MetaFilter posts tagged with evolution

Important communication skills

Brandon Blatcher — Wed, 15 May 2013 14:55:53 -0800

Use "Metatalk" skill to discuss communication problems.

Why I Study Duck Genitalia

Blasdelb — Fri, 03 May 2013 14:28:46 -0800

In the past few days, the Internet has been filled with commentary on whether the National Science Foundation should have paid for my study on duck genitalia, and 88.7 percent of respondents to a Fox news online poll agreed that studying duck genitalia is wasteful government spending. The commentary supporting and decrying the study continues to grow. As the lead investigator in this research, I would like to weigh in on the controversy and offer some insights into the process of research funding by the NSF.

Come for the passionate defense of basic science, stay for the explosive eversion of a duck penis.

Open access research published from this work:

The limits of sexual conflict in the narrow sense: new insights from waterfowl biology PLR Brennan & RO Prum Sexual conflict occurs when the evolutionary interests of the sexes differ and it broadly applies to decisions over mating, fertilization and parental investment. Recently, a narrower view of sexual conflict has emerged in which direct selection on females to avoid male-imposed costs during mating is considered the distinguishing feature of conflict, while indirect selection is considered negligible. In this view, intersexual selection via sensory bias is seen as the most relevant mechanism by which male traits that harm females evolve, with antagonistic coevolution between female preferences and male manipulation following. Under this narrower framework, female preference and resistance have been synonymized because both result in a mating bias, and similarly male display and coercion are not distinguished. Our recent work on genital evolution in waterfowl has highlighted problems with this approach. In waterfowl, preference and resistance are distinct components of female phenotype, and display and coercion are independent male strategies. Female preference for male displays result in mate choice, while forced copulations by unpreferred males result in resistance to prevent these males from achieving matings and fertilizations. Genital elaborations in female waterfowl appear to function in reinforcing female preference to maintain the indirect benefits of choice rather than to reduce the direct costs of coercive mating. We propose a return to a broader view of conflict where indirect selection and intrasexual selection are considered important in the evolution of conflict. Coevolution of Male and Female Genital Morphology in Waterfowl PLR Brennan, RO Prum, KG McCracken, MD Sorenson, RE Wilson & TR Birkhead Most birds have simple genitalia; males lack external genitalia and females have simple vaginas. However, male waterfowl have a phallus whose length (1.5–>40 cm) and morphological elaborations vary among species and are positively correlated with the frequency of forced extra-pair copulations among waterfowl species. Here we report morphological complexity in female genital morphology in waterfowl and describe variation vaginal morphology that is unprecedented in birds. This variation comprises two anatomical novelties: (i) dead end sacs, and (ii) clockwise coils. These vaginal structures appear to function to exclude the intromission of the counter-clockwise spiralling male phallus without female cooperation. A phylogenetically controlled comparative analysis of 16 waterfowl species shows that the degree of vaginal elaboration is positively correlated with phallus length, demonstrating that female morphological complexity has co-evolved with male phallus length. Intersexual selection is most likely responsible for the observed coevolution, although identifying the specific mechanism is difficult. Our results suggest that females have evolved a cryptic anatomical mechanism of choice in response to forced extra-pair copulations. Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia PLR Brennan, CJ Clark & RO Prum Coevolution of male and female genitalia in waterfowl has been hypothesized to occur through sexual conflict. This hypothesis raises questions about the functional morphology of the waterfowl penis and the mechanics of copulation in waterfowl, which are poorly understood. We used high-speed video of phallus eversion and histology to describe for the first time the functional morphology of the avian penis. Eversion of the 20 cm muscovy duck penis is explosive, taking an average of 0.36 s, and achieving a maximum velocity of 1.6 m s−1. The collagen matrix of the penis is very thin and not arranged in an axial-orthogonal array, resulting in a penis that is flexible when erect. To test the hypothesis that female genital novelties make intromission difficult during forced copulations, we investigated penile eversion into glass tubes that presented different mechanical challenges to eversion. Eversion occurred successfully in a straight tube and a counterclockwise spiral tube that matched the chirality of the waterfowl penis, but eversion was significantly less successful into glass tubes with a clockwise spiral or a 135° bend, which mimicked female vaginal geometry. Our results support the hypothesis that duck vaginal complexity functions to exclude the penis during forced copulations, and coevolved with the waterfowl penis via antagonistic sexual conflict.

The rise of the tick

Blasdelb — Thu, 02 May 2013 09:28:57 -0800

With incisor-like claws that can tunnel beneath your skin in seconds, ticks are rapidly establishing themselves as the Swiss Army knife of disease vectors. Carl Zimmer walks into the woods to find out why these tiny beasts appear to be skyrocketing in number – and outsmarting environmental scientists trying to control them with every bite.

“Rituals are the glue that holds social groups together.”

the man of twists and turns — Tue, 23 Apr 2013 20:56:15 -0800

Social Evolution - The Ritual Animal "Praying, fighting, dancing, chanting — human rituals could illuminate the growth of community and the origins of civilization."

Legare presented Brazilians with a variety of simpatias, and found that people judged them as more effective when they involved a large number of repetitive procedural steps that must be performed at a specific time and in the presence of religious icons. “We're built to learn from others,” she says, which leads us to repeat actions that seemed to work for someone else — “even if we don't understand how they produce the desired outcomes”.

Human Rites: "Rituals bind us, in modern societies and prehistoric tribes alike. But can our loyalties stretch to all of humankind?"

Human populations living side-by-side tend to have a lot in common. They adopt the same basic techniques of production, use similar tools and natural resources, live in similar kinds of houses and so on. At the level of practical affairs, there might be little to tell them apart. However, their rituals are a different story altogether. Arbitrary conventions on how to achieve certain goals — placate the gods, or ensure an adequate crop — can assume any pattern: in straightforward physical terms, they don’t actually have to do anything. And yet they are far from impotent. Indeed, in social terms they can have very significant effects. To start with, they serve as admirable group markers precisely because they are of no use to those outside the group. And they don’t just demarcate people. Rituals also bind them together. How? And how far can they stretch?

via Overcoming Bias: Farmer's New Rituals The University of Oxford's Institute Of Cognitive And Evolutionary Anthropology's Ritual, Community & Conflict Project. Markets, Community Size, And The Evolution Of Fairness And Punishment (PDF)

These results suggest that modern prosociality is not solely the product of an innate psychology, but also reflects norms and institutions that have emerged over the course of human history.

The Adaptive Value Of Religious Ritual (PDF)

Religion has probably always served to enhance the union of its practitioners; unfortunately, there is also a dark side to this unity. If the intragroup solidarity that religion promotes is one of its significant adaptive benefits, then from its beginning religion has probably always played a role in intergroup conflicts. In other words, one of the benefits for individuals of intragroup solidarity is the ability of unified groups to defend and compete against other groups.

The Glue That Binds Ritual Is Power The Primacy Of Ritual Over Language Emile Durkheim: religion – the very idea, part 1: the analysis of moral life "Durkheim's work on the sacred offers a starting point for a public language for thinking about the moral basis for society"

Selection pressure

Blazecock Pileon — Mon, 08 Apr 2013 14:49:29 -0800

Researchers have found that size does matter as it relates to overall proportions of the male body (PNAS link, PDF)

Iterated learning using YouTube

knile — Tue, 02 Apr 2013 08:09:45 -0800

"What happens if you repeatedly run Kafka's Metamorphosis through YouTube's auto-transcription? Structure emerges!" via Sean Roberts

Evolution: Maybe It's Not Just for the Fittest Anymore

saulgoodman — Thu, 28 Mar 2013 07:48:40 -0800

Is it time to put natural selection in its place? Jello Biafra once famously wrote that "If evolution is outlawed, only outlaws will evolve." But while it likely comes as no surprise to specialists working in the field or to those who've been following developments in evolutionary biology closely, there's an emerging view among experts that Darwin's view of natural selection as the primary driver of speciation and evolutionary change may be incorrect or at least drastically overstated. It's long been understood that non-adaptive evolutionary mechanisms like "genetic drift" and random mutation also play non-trivial roles in evolutionary processes, but a recent study (link to abstract with full-text PDF available) casts new doubts on the primary role of natural selection, finding that "Neutral models, in which genetic change arises through random variation without fitness differences have proven remarkably successful in describing observed patterns of biodiversity." Meanwhile, America's obsession with competitive fitness as virtue remains a conspicuous feature of the culture despite the evolving science of evolution, and newer scientific fields like Evolutionary Psychology continue to operate under the assumption that adaptive fitness is the primary driver of evolutionary processes.

Nagel on the Materialist Neo-Darwinian Conception of Nature

shivohum — Tue, 19 Mar 2013 07:02:18 -0800

Andrew Ferguson explains and defends eminent philosopher Thomas Nagel, who has been stirring up outraged refutations (e.g. here or here) with his new book Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False. Also in the defense column is philosopher Edward Feser's extensive series on Nagel's book.

sea & sky

kliuless — Mon, 18 Mar 2013 20:11:11 -0800

seaQuest: what if we could learn to live on/underneath the oceans (or in orbit)? [prev iou sly(er)] also btw... -Why Utopia? -Envisioning Real Utopias -Utopianism, Conservatism, Ideal Theory: Who is Trying to Get Where, From Here?

Faces of Human Ancestors

lazaruslong — Mon, 04 Mar 2013 13:30:52 -0800

To put a human face on our ancestors, scientists from the Senckenberg Research Institute used sophisticated methods to form 27 model heads based on tiny bone fragments, teeth and skulls collected from across the globe. Here is a video showing those different models morphing into one another. Original article here. [via] The Discovery article has descriptions of the various models and sources and stuff in the caption bar.

♫

Fizz — Sat, 23 Feb 2013 07:59:58 -0800

Evolution of Mom Dancing [SLYT] In honor of the First Lady's "Let's Move" campaign, and to encourage parents everywhere to get up and get moving with their kids, Jimmy Fallon and Michelle Obama present the "Evolution of Mom Dancing."

It is raining spiders in Brazil.

Blasdelb — Sat, 09 Feb 2013 12:20:13 -0800

"Hundreds (maybe thousands) of spiders congregate between poles in the town of Santo Antonio de Plantina / PR." According to G1 (Portugese), "A biologist who specializes in spiders of the Pontifical Catholic University of Paraná (PUC-PR), Marta Fischer, examined the picture and said that the phenomenon is normal and occurs mainly in the cities of São Paulo. "It is the kind of spider known as Anelosimus Eximius, which are social spiders. They are usually in trees during the day and in the late afternoon and early evening construct a sort of sheet webs, each makes his and then they come together. The goal is to capture insects," she explains, "During the day they destroy the webs to prevent birds do it," concludes Marta, who also said that the venom of this species causes no risks to humans." These spiders work together to take down much larger prey than they could otherwise alone, as David Attenborough beautifully demonstrates on film

Benefits of cooperation with genetic kin in a subsocial spider Interaction within groups exploiting a common resource may be prone to cheating by selﬁsh actions that result in disadvantages for all members of the group, including the selﬁsh individuals. Kin selection is one mechanism by which such dilemmas can be resolved This is because selﬁsh acts toward relatives include the cost of lowering indirect ﬁtness beneﬁts that could otherwise be achieved through the propagation of shared genes. Kin selection theory has been proved to be of general importance for the origin of cooperative behaviors, but other driving forces, such as direct ﬁtness beneﬁts, can also promote helping behavior in many cooperatively breeding taxa. Investigating transitional systems is therefore particularly suitable for understanding the inﬂuence of kin selection on the initial spread of cooperative behaviors. Here we investigated the role of kinship in cooperative feeding. We used a cross-fostering design to control for genetic relatedness and group membership. Our study animal was the periodic social spider Stegodyphus lineatus, a transitional species that belongs to a genus containing both permanent social and periodic social species. In S. lineatus, the young cooperate in prey capture and feed communally. We provide clear experimental evidence for net beneﬁts of cooperating with kin. Genetic relatedness within groups and not association with familiar individuals directly improved feeding efﬁciency and growth rates, demonstrating a positive effect of kin cooperation. Hence, in communally feeding spiders, nepotism favors group retention and reduces the conﬂict between selﬁsh interests and the interests of the group.

More information on the spider:

Social spiders catch larger prey: a study of Anelosimus eximius (Araneae: Theridiidae) During a 1-year-study in tropical Panama, prey of the social theridiid Anelosimus eximius was analysed at two locations and compared with the potential prey spectrum according to sweepnet catches, pitfall traps and bowl traps. Compared with other web-building spiders, A. eximius catch an unusually high number of large insects: about 90% are flying ants, beetles,lepidopterans hemipterans, cockroaches and grasshoppers. This is the result of a communal strategy to overwhelm prey. Webs are maintained commonly, and several spiders attack an entangled insect simultaneously. More spiders participate on insects that are larger and struggle more. The ability to catch large prey insects is discussed as a major driving factor for sociality in spiders. Population genetics of Anelosimus eximius (Araneae, Theridiidae) Anelosimus eximius is a cooperative, group-living neotropical spider. Colonies consist of up to several thousand individuals, and colonies may be aggregated into local colony clusters. The colony clusters are patchily distributed, and are often separated from their neighbors by a km or more. In this study individuals were collected from colonies located in Panama and Suriname. These individuals were subjected to horizontal starch gel electrophoresis and screened for polymorphisms in 46 enzyme systems. A total of 51 scorable loci were found, of which seven were polymorphic. The results were analyzed with Wright's F statistics which were used to investigate the amount of genetic differentiation in the population attributable to subdivision of the population into colonies, colony clusters, local populations and the geographic regions of Panama and Suriname. Most of the genetic differentiation in the A. eximius sampled was due to subdivision of the population into colony clusters and into geographic regions. There was no evidence of differentiation among colonies in a colony cluster, and little differentiation among collection sites within Panama or Suriname. In contrast, within a local population, samples from adjacent colony clusters were sometimes fixed for different alleles at one or more loci, and the Panama and Suriname samples were fixed for different alleles at three loci.

(The spider previously)

"In the future, everything will be terrifying."

the man of twists and turns — Wed, 30 Jan 2013 11:35:30 -0800

Dougal Dixon is a scientist, author, and illustrator. While he is most famous for his work on dinosaurs, his books After Man: A Zoology of the Future and Man After Man: An Anthropology Of The Future attempt to explore what might happen in the far future. The Posthuman Art Of Dougal Dixon. Obscure Dougal Dixon stuff!, including a Japanese documentary.

For the study of nature and the search for truth

barnacles — Tue, 29 Jan 2013 00:15:51 -0800

Even though you've heard of Darwin, it's quite possible that you're not familiar with Alfred Russel Wallace (previously), co-discoverer of the theory of evolution (a shame; in many respects he's the more interesting of the two!). Fortunately you can now learn more about the man through transcripts and scans of his letters with family and colleagues, which the UK Natural History Museum have just published online. This is part of the Wallace100 project, celebrating the centenary of his death.

A pelican that looks like a urinal

escabeche — Wed, 16 Jan 2013 18:04:17 -0800

Go home, evolution, you're drunk. A photo of a pelican that looks like a urinal. Brought to you by WTF, Evolution?

Eight criticisms not to make about group selection

Blasdelb — Tue, 15 Jan 2013 08:35:01 -0800

Group selection, which was once widely rejected as a significant evolutionary force, is now accepted by all who seriously study the subject. There is still widespread confusion about group selection, however, not only among students and the general public, but among professional evolutionists who do not directly study the subject. We list eight criticisms that are frequently invoked against group selection, which can be permanently laid to rest based upon current knowledge. Experts will always find something to critique about group selection, as for any important subject, but these eight criticisms are not among them. Laying them to rest will enable authors to openly use the term group selection without being handicapped during the review process. [HTML], [PDF]

"it's quite clear that there's tons of cultural transmission that's just strictly by observational learning."

the man of twists and turns — Fri, 04 Jan 2013 08:52:07 -0800

How Culture Drove Human Evolution

Projectile Shit Vomiting For the Win

Blasdelb — Thu, 03 Jan 2013 12:32:25 -0800

The Norovirus: A Study in Puked Perfection, "Each norovirus carries just nine protein-coding genes (you have about 20,000). Even with that skimpy genetic toolkit, noroviruses can break the locks on our cells, slip in, and hack our own DNA to make new noroviruses. The details of this invasion are sketchy, alas, because scientists haven’t figured out a good way to rear noroviruses in human cells in their labs. It’s not even clear exactly which type of cell they invade once they reach the gut. Regardless of the type, they clearly know how to exploit their hosts. Noroviruses come roaring out of the infected cells in vast numbers. And then they come roaring out of the body. Within a day of infection, noroviruses have rewired our digestive system so that stuff comes flying out from both ends." Linked articles cited by Zimmer:

Noroviruses: The Perfect Human Pathogens? Noroviruses are perhaps the perfect human pathogens. These viruses possess essentially all of the attributes of an ideal infectious agent: highly contagious, rapidly and prolifically shed, constantly evolving, evoking limited immunity, and only moderately virulent, allowing most of those infected to fully recover, thereby maintaining a large susceptible pool of hosts. These characteristics have enabled noroviruses to become the leading cause of endemic diarrheal disease across all age groups [1], the leading cause of foodborne disease [2], and the cause of half of all gastroenteritis outbreaks worldwide [3]. In the United States alone, noroviruses are responsible for an estimated 21 million cases of acute gastroenteritis annually, including >70 000 hospitalizations and nearly 800 deaths [2] [4] [5]. In developing countries, where the greatest burden of diarrheal disease occurs, noroviruses have been estimated to cause up to 200 000 deaths each year in children < 5 years of age [6]. Although recognition of this immense disease burden is relatively recent, it is unclear whether it has long been present and failed to be recognized because of lack of sensitive diagnostics or if, in fact, noroviruses represent a truly emergent public health issue [7]. Regardless, attempts to address the overwhelming burden of norovirus disease first require an understanding of the complexity and efficiency with which these viruses spread. Pathogenesis of Noroviruses, Emerging RNA Viruses Human noroviruses in the family Caliciviridae are a major cause of epidemic gastroenteritis. They are responsible for at least 95% of viral outbreaks and over 50% of all outbreaks worldwide. Transmission of these highly infectious plus-stranded RNA viruses occurs primarily through contaminated food or water, but also through person-to-person contact and exposure to fomites. Norovirus infections are typically acute and self-limited. However, disease can be much more severe and prolonged in infants, elderly, and immunocompromised individuals. Norovirus outbreaks frequently occur in semi-closed communities such as nursing homes, military settings, schools, hospitals, cruise ships, and disaster relief situations. Noroviruses are classified as Category B biodefense agents because they are highly contagious, extremely stable in the environment, resistant to common disinfectants, and associated with debilitating illness. The number of reported norovirus outbreaks has risen sharply since 2002 suggesting the emergence of more infectious strains. There has also been increased recognition that noroviruses are important causes of childhood hospitalization. Moreover, noroviruses have recently been associated with multiple clinical outcomes other than gastroenteritis. It is unclear whether these new observations are due to improved norovirus diagnostics or to the emergence of more virulent norovirus strains. Regardless, it is clear that human noroviruses cause considerable morbidity worldwide, have significant economic impact, and are clinically important emerging pathogens. Despite the impact of human norovirus-induced disease and the potential for emergence of highly virulent strains, the pathogenic features of infection are not well understood due to the lack of a cell culture system and previous lack of animal models. This review summarizes the current understanding of norovirus pathogenesis from the histological to the molecular level, including contributions from new model systems. Tracking Environmental Norovirus Contamination in a Pediatric Primary Immunodeficiency Unit Norovirus strains were detected in two patients and in environmental swabs from a pediatric primary immunodeficiency unit in London, United Kingdom, during an infection control incident in November and December 2007. Detailed analyses of the gene encoding the P2 domain demonstrated that the majority of the strains were not related to the patients and that the environmental contamination was most likely due to secondary transfer by the hands of staff or visitors. A Point-Source Norovirus Outbreak Caused by Exposure to Fomites We investigated a norovirus outbreak (genotype GII.2) affecting 9 members of a soccer team. Illness was associated with touching a reusable grocery bag or consuming its packaged food contents (risk difference, 0.636; P < .01). By polymerase chain reaction, GII norovirus was recovered from the bag, which had been stored in a bathroom used before the outbreak by a person with norovirus-like illness. Airborne contamination of fomites can lead to subsequent point-source outbreaks. When feasible, we recommend dedicated bathrooms for sick persons and informing cleaning staff (professional or otherwise) about the need for adequate environmental sanitation of surfaces and fomites to prevent spread. Recurring Norovirus Transmission on an Airplane Previously reported outbreaks of norovirus gastroenteritis associated with aircraft have been limited to transmission during a single flight sector. During October 2009, an outbreak of diarrhea and vomiting occurred among different groups of flight attendants who had worked on separate flight sectors on the same airplane. We investigated the cause of the outbreak and whether the illnesses were attributable to work on the airplane. Information was obtained from flight attendants on demographic characteristics, symptoms, and possible transmission risk factors. Case patients were defined as flight attendants with diarrhea or vomiting <51 hours after the end of their first flight sector on the airplane during 13–18 October 2009. Stool samples were tested for norovirus RNA. A passenger had vomited on the Boeing 777-200 airplane on the 13 October flight sector. Sixty-three (82%) of 77 flight attendants who worked on the airplane during 13–18 October provided information, and 27 (43%) met the case definition. The attack rate among flight attendants decreased significantly over successive flight sectors from 13 October onward (P < .001). Working as a supervisor was independently associated with development of illness (adjusted odds ratio, 5.8; 95% confidence interval, 1.3–25.6). Norovirus genotype GI.6 was detected in stool samples from 2 case patients who worked on different flight sectors. Sustained transmission of norovirus is likely to have occurred because of exposures on this airplane during successive flight sectors. Airlines should make provision for adequate disinfection of airplanes with use of products effective against norovirus and other common infectious agents after vomiting has occurred. Norovirus Vaccine against Experimental Human Norwalk Virus Illness Noroviruses cause epidemic and sporadic acute gastroenteritis. No vaccine is available to prevent norovirus illness or infection. We conducted a randomized, double-blind, placebo-controlled, multicenter trial to assess the safety, immunogenicity, and efficacy of an investigational, intranasally delivered norovirus viruslike particle (VLP) vaccine (with chitosan and monophosphoryl lipid A as adjuvants) to prevent acute viral gastroenteritis after challenge with a homologous viral strain, Norwalk virus (genotype GI.1). Healthy adults 18 to 50 years of age received two doses of either vaccine or placebo and were subsequently inoculated with Norwalk virus and monitored for infection and gastroenteritis symptoms. Ninety-eight persons were enrolled and randomly assigned to receive vaccine (50 participants) or placebo (48 participants), and 90 received both doses (47 participants in the vaccine group and 43 in the placebo group). The most commonly reported symptoms after vaccination were nasal stuffiness, nasal discharge, and sneezing. Adverse events occurred with similar frequency among vaccine and placebo recipients. A Norwalk virus–specific IgA seroresponse (defined as an increase by a factor of 4 in serum antibody levels) was detected in 70% of vaccine recipients. Seventy-seven of 84 participants inoculated with Norwalk virus were included in the per-protocol analysis. Vaccination significantly reduced the frequencies of Norwalk virus gastroenteritis (occurring in 69% of placebo recipients vs. 37% of vaccine recipients, P=0.006) and Norwalk virus infection (82% of placebo recipients vs. 61% of vaccine recipients, P=0.05). This norovirus VLP vaccine provides protection against illness and infection after challenge with a homologous virus. (Funded by LigoCyte Pharmaceuticals and the National Institutes of Health; ClinicalTrials.gov number, NCT00973284.)

Parasite manipulation of host behavior previously: Deciphering the Tools of Nature’s Zombies

Woese once said of himself and his work that when a wise man points out the moon, only a fool looks at the finger. Let us all be fools if just for a moment .

Blasdelb — Wed, 02 Jan 2013 07:29:30 -0800

Microbiology's Scarred Revolutionary^(PDF), Carl Woese (pron.: /ˈwoʊz/), a biophysicist and evolutionary microbiologist whose discovery 35 years ago of a “third domain” of life in the vast realm of micro-organisms altered scientific understanding of evolution, died on Sunday at his home in Urbana, Ill. He was 84. “Imagine walking out in the countryside and not being able to tell a snake from a cow from a mouse from a blade of grass, that’s been the level of our ignorance.”-Woese

Carl Woese's distinguished career was dominated by his idea that divisions between different kinds of living organisms could be better defined by their small subunit ribosomal RNA^{(smaller bottom piece here)} sequences than by their morphology, biochemistry, outer membrane, or even necessarily the most basic of divisions like multicellularity or the presence of cellular organelles. Indeed, seeing life through this much clearer lens, he was able to show that the microbes known as Archaea are at least as different from Bacteria as they are from Eukaryotes like plants and animals, a finding he presented here to much controversy and derision:
Woese, Carl R.; George E. Fox (1977). "Phylogenetic structure of the prokaryotic domain: the primary kingdoms.^(PDF)". Proceedings of the National Academy of Sciences of the United States of America 74 (11): 5088–5090 A phylogenetic analysis based upon ribosomal RNA sequence characterization reveals that living systems represent one of three aboriginal lines of descent: (i) the eubacteria, comprising all typical bacteria; (ii) the archaebacteria, containing methanogenic bacteria; and (iii) the eurkaryotes, now represented in the cytoplasmic component of eukaryotic cells.
Fought for eloquently here:
Woese, Carl R. (1987-06-01). "Bacterial evolution.^(PDF)". Microbiological Reviews 51 (2): 221–271 A revolution is occurring in biology: perhaps it is better characterized as a revolution within a revolution. I am, of course, referring to the impact that the increasingly rapid capacity to sequence nucleic acids is having on a science that has already been radically transformed by molecular approaches and concepts. While the impact is currently greatest in genetics and applied areas such as medicine and biotechnology, its most profound and lasting effect will be on our perception of evolution and its relationship to the rest of biology. The cell is basically an historical document, and gaining the capacity to read it (by the sequencing of genes) cannot but drastically alter the way we look at all of biology. No discipline within biology will be more changed by this revolution than microbiology, for until the advent of molecular sequencing, bacterial evolution was not a subject that could be approached experimentally. With any novel scientific departure it is important to understand the historical setting in which it arises-the paradigm it will change. Old prejudices tend to inhibit, distort, or otherwise shape new ideas, and historical analysis helps to eliminate much of the negative impact of the status quo. Stch analysis is particularly importaht in the present instance since microbiologists do not deal with evolutionary considerations as a matter of course and so tend not to appreciate them. Therefore, I begin this discussion with a brief look at how the relationship between microbiology and evolution (i.e., the lack thereof) developed.
And presented again thirteen years later, this time as core scientific dogma:
Woese, C R; O Kandler, M L Wheelis (1990). "Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya.^(PDF)". Proceedings of the National Academy of Sciences of the United States of America 87 (12): 4576–4579. Molecular structures and sequences are generally more revealing of evolutionary relationships than are classical phenotypes (particularly so among microorganisms). Consequently, the basis for the definition of taxa has progressively shifted from the organismal to the cellular to the molecular level. Molecular comparisons show that life on this planet divides into three primary groupings, commonly known as the eubacteria, the archaebacteria, and the eukaryotes. The three are very dissimilar, the differences that separate them being of a more profound nature than the differences that separate typical kingdoms, such as animals and plants. Unfortunately, neither of the conventionally accepted views of the natural relationships among living systems--i.e., the five-kingdom taxonomy or the eukaryote-prokaryote dichotomy--reflects this primary tripartite division of the living world. To remedy this situation we propose that a formal system of organisms be established in which above the level of kingdom there exists a new taxon called a "domain." Life on this planet would then be seen as comprising three domains, the Bacteria, the Archaea, and the Eucarya, each containing two or more kingdoms. (The Eucarya, for example, contain Animalia, Plantae, Fungi, and a number of others yet to be defined). Although taxonomic structure within the Bacteria and Eucarya is not treated herein, Archaea is formally subdivided into the two kingdoms Euryarchaeota (encompassing the methanogens and their phenotypically diverse relatives) and Crenarchaeota (comprising the relatively tight clustering of extremely thermophilic archaebacteria, whose general phenotype appears to resemble most the ancestral phenotype of the Archaea.

“It’s clear to me that if you wiped all multicellular life-forms off the face of the earth, microbial life might shift a tiny bit, if microbial life were to disappear, that would be it — instant death for the planet.”-Woese

Later in life he became something of an elder statesman of evolutionary microbiology publishing the occasional review:
Woese, Carl R.; Nigel Goldenfeld (2009). "How the Microbial World Saved Evolution from the Scylla of Molecular Biology and the Charybdis of the Modern Synthesis". Microbiology and Molecular Biology Reviews 73 (1): 14–21. In this commentary, we provide a personal overview of the conceptual history of microbiology and molecular biology over the course of the last hundred years, emphasizing the relationship of these fields to the problem of evolution. We argue that despite their apparent success, all three reached an impasse that arose from the influence of dogmatic or overly narrow perspectives. Finally, we describe how recent developments in microbiology are realizing Beijerinck's vision of a field that is fully integrated with molecular biology, microbial ecology, thereby challenging and extending current thinking in evolution.

Today, whenever a student of biology opens their textbook what they see first is a blown up image of the tripartite tree of life – a small tribute to a man and a discovery that changed our view of nature forever."

State of Nature

escabeche — Sat, 29 Dec 2012 18:21:47 -0800

“When I spoke at the two Ron Paul events in Tampa, a young man kind enough to pick me up at the airport told me a fascinating story. The vast majority of young Ron volunteers in offices he visited all over the country were paleo. If a kid ordered pizza — which was always the primary or perhaps only campaign food — he was practically booed,” Atossa Araxia Abrahamian writes in The New Inquiry about the paleo diet, libertarianism, and the appealing idea of a healthy, undistorted state of nature to which we can return if we are only pure enough. Abrahamian makes much use of the work of Marlene Zuk, an evolutionary biologist at the University of Minnesota who wrote in the New York Times three years ago: "As an evolutionary biologist, I was filled with enthusiasm at first over the idea of a modern mismatch between everyday life and our evolutionary past. But a closer look reveals that not all evolutionary ideas are created equal; even for Darwinians, the devil is in the details. The notion that there was a time of perfect adaptation, from which we’ve now deviated, is a caricature of the way evolution works."

Japan

kliuless — Thu, 27 Dec 2012 15:56:07 -0800

What's Going On In Japan? "Really Japan is quite a remarkable case, since neither fiscal nor monetary policy seems to be working to achieve the anticipated results. This year Japan will have a fiscal deficit of around 10% of GDP and gross government debt will hit 235% of GDP, yet the country is still struggling to find growth. Instead of reiterating old dogmas (whether they come from Keynes or from Hayek) more people should be asking themselves what is happening here. This is not a simple repetition of something which was first time tragedy and is now second time tragedy, it is something new, and could well be a harbinger for more that is to come, elsewhere. Oh, why oh why are economists not more curious?" Time to Japanic? "About half of the Japanese government's annual budget now goes to pensions and interest payments... With projected annual budget deficits between 7 and 10 percent of GDP, Japanese savers are essentially tendering their savings in return for newly issued government debt, which is not backed by hard assets. It is backed only by an aging, shrinking population of taxpayers... A crisis in Japan would most likely manifest as a collapse of confidence in the yen: At some point, Japanese citizens will decide that saving in any yen-denominated asset is not worth the risk. Then interest rates will rise; the capital position of banks, insurance companies, and pension funds will worsen (because they all hold long-maturing bonds, which fall in value when rates rise); and fears of insolvency will surface..."

If Japan doesn't change course, it will have a major crisis within the next decade. If. But what people need to understand is, the Japanese government does have the power to avert a crisis. It is not inevitable. There is one way that the crisis can definitely be averted: Raise taxes. Japan's fiscal woes can be boiled down to one sentence: Japan has European levels social spending and European levels of aging with American levels of taxation. But this could change; if Japan raised taxes to European levels, crisis would be instantly averted. According to analyses I've seen, this would require raising Japan's taxes from their current level of 32.5% of GDP to somewhere between 40% and 50% of GDP. That's comparable to France or Sweden. Painful, but not impossible. Now for the rumor (rumor always being a large component in Western analyses of Japan). My sources at the Bank of Japan and Ministry of Finance tell me that domestic Japanese investors are betting that, after all the grumbling and fighting and ending of political careers, Japan's government will suck it up and raise taxes. This, my shadowy sources say, is why pension funds are still willing to put the Japanese people's money into JGBs. But this story is not really outlandish. It's similar to what we're observing in America right now. U.S. borrowing is at all-time highs, but demand for Treasuries shows no sign of flagging, and most of that demand - more than in the past - is from domestic U.S. investors. Yes, we have shown a reluctance to raise taxes - witness the apocalyptic debt ceiling fight from last year. But if the public really thought the U.S. government was willing to default, domestic Treasury buyers would be heading for the exits. That they are not heading for the exits probably indicates that they believe that when push comes to shove, the U.S. government will suck it up and raise taxes. There are signs that the Republicans are quietly recognizing the necessity of this. At this point, it's just a fight between Democrats and Republicans to see who takes the fall for raising taxes - that's what the "fiscal cliff" is really all about. Japan seems to be in a similar situation. It is not really unusual or outlandish at all. Everyone in the country still seems to believe that the government will continue to function. The day that that belief falters - or is proven wrong by main force, when interest payments swamp the primary budget - is the day that Japan collapses (the same goes for the U.S.). But if Japan's government is less dysfunctional than the often skittish Western press believes, that day will never come. (Anyway... oh yeah, I did mention that there might be two ways out of Japan's fiscal trap, didn't I? The other way is to use monetary policy to create negative real interest rates for a very long period of time. If that can be done in a stable way (without accelerating inflation) and if stable growth persists, then Japan can use an "inflation tax" to erode the value of its government debt instead of an actual tax. Econ bloggers (and commenters), who tend to believe that central banks can hit any NGDP target they want, will probably advocate this "solution"...)

Is Japan set to lead after 20 years of torpor?

But while a revolution is under way in the attitude to economic targets, the new tools and instruments required to hit these targets have hardly begun to be discussed. The unemployment and GDP targets suggested by Bernanke and Carney are empty promises in the absence of policy tools that could convincingly boost jobs and growth in the present deflationary environment. Which is where Japan comes in. No other economy has (yet) suffered anything like Japan's 20 years of economic stagnation. It would not be surprising, therefore, if truly radical measures to deal with deflation were pioneered in Japan. Outside Japan, no central banker or politician has yet gone beyond pumping money into bond markets through quantitative easing. And nobody has suggested, at least officially, that central banks should directly lend to governments or finance one-off tax cuts.

This election may be different in Japan

The Japanese election on 16 December is attracting intense interest in the global financial markets. In part, this is because the LDP's election campaign, led by Mr Shinzo Abe, is based on forcing an entirely new monetary strategy on the Bank of Japan, with obvious consequences for the yen and the equity market. On top of that, the Japanese election is the first in a major democracy where the role and mandate of the central bank has taken centre stage in a national political campaign. Is this the shape of things to come in other democracies facing low growth, subdued inflation and rising government debt ratios? Politicians in many other developed economies will be watching the Japanese experiment with rapt attention... As the population ages, the savings ratio will fall further, and the government will be forced to look overseas for the financing of its rising debt burden. An important recent study by Takeo Hoshi and Takatoshi Ito concludes that this is likely to result in a government debt crisis well within a decade. Markets are forward looking, and will see this coming well in advance. Japan has defied the debt crisis doom-mongers for more than a decade now, but its long term deteriorating trends on demography, government debt and export performance cannot be held at bay indefinitely. Shinzo Abe has concluded that the only way out of this dilemma is to force the Bank of Japan to raise the inflation rate and (though he does not say this specifically) push the yen down. Unsterilised purchases of foreign assets may be the only way the central bank can do this. Of course, there are severe risks with the Abe programme. If inflation expectations rise, bond yields may follow suit, undermining the capital base of the financial sector which holds all the bonds. But the Japanese political wind is now blowing strongly in the direction of co-opting the central bank as an integral arm of the government. If Mr Abe does not do it, someone else almost certainly will.

A Conversation with Ray Dalio

I give the example of Japan because when you're looking at the United States, the Japan example, I think, is a very good example. We have -- Japan has total debt-to-GDP of about 500 percent, and it has government debt-to-GDP of about 270 percent. So it is way, way, way more leveraged, in a sense, than the United States is. And so then the question is, as we go through this, the magnitude of monetization. You have to go back to say, who are the buyers of the debt and what are the motivations? There is a "greater fool" theory. The "greater fool" theory can go on for a really long time. The timing of when that shift takes place is very much dependent on that. So as we look in terms of, let's say, the United Sates, certainly it's the case -- and in Japan -- certainly it's the case that we can't support these kinds of debt. Anybody with a sharp pencil will know that we're not going to be able to support that. That doesn't mean there won't be adequate buy, just like in Japan's case. You can have plenty of buy. You provide enough liquidity, and the question is, what are the choices?

Rational astrologies: "The process by which rational astrologies are chosen is the process by which the world is ruled. The United States is the world's financial power because it is conventional to pretend that the US dollar is a safe asset, and so long as it is conventional it is true and so the convention is very difficult to dislodge. Economics as a discipline has not performed very well from the perspective of commonsensical outside observers like the Queen of England. But the conventions of economic analysis are the rational astrology of technocratic government, and decisions that can't be couched and justified according to those conventions cannot be safely taken by policy makers. Policy is largely a side effect of the risk-averse behavior of political careerists, who rationally parade their adherence to this moment's conventions as enthusiastically as noblemen deferred to pronouncements of a court astrologer in an earlier time. We can only hope that our era's conventions engender better policy as a side-effect than attention to the movement of the stars. (As far as I am concerned, the jury is still out.) But it is not individuals' independent judgment of the wisdom of these conventions that guides collective behavior. Our behavior, and often our sincere beliefs, are largely formed in reaction to the terrifying accountability that comes with making consequential choices unconventionally. Our rational astrologies are at the core of who we are, as individuals and as societies." Central banks make an historic turn

When the economic history of the 21st century is written, September 2012 is likely to be recorded as a defining moment, almost as important as September 2008. This month's historic events – Ben Bernanke’s promise to buy bonds without limit until the U.S. returns to something approaching full employment, Angela Merkel's support for the European Central Bank bond purchase plans and the Bank of Japan's decision to accelerate greatly its easing program – may not seem earth-shattering in the same way as the near-collapse of every major bank in the U. S. and Europe. Yet the upheavals now happening in central banking represent a tectonic shift that could transform the economic landscape as dramatically as the financial earthquake four years ago. To see why, we must go back in history 40 years, to the early 1970s. Maintaining full employment was at that time regarded as the main objective of all economic policy, and this had been the case for roughly 40 years, since the Great Depression. But by the early 1970s, voters had enjoyed decades of more or less full employment and were starting to focus on inflation rather than depression as the main threat to their prosperity. Economists and politicians were responding to this shift. Milton Friedman led a monetarist "counterrevolution" against the Keynesian obsession with unemployment, designing new economic models to challenge the Keynesian view that market economies were naturally prone to long-term stagnation. By restoring the pre-Keynesian assumption that market economies were automatically self-stabilizing, the monetarist models produced two powerful policy prescriptions directly opposed to the Keynesian views. First, the monetarists insisted that price stability, rather than full employment, was the only legitimate target for monetary policy and government macroeconomic management more generally. Second, they argued that central bankers should not accept any direct responsibility for unemployment, since sustainable job creation depended solely on private enterprise – full employment would be achieved automatically if inflation were conquered and market forces were allowed to operate freely, with the minimum of government interference or union constraints. A few years later, Margaret Thatcher and Ronald Reagan turned Friedman's intellectual revolution into practical politics. On top of its economic impact, monetarism had huge ideological effects by absolving government macroeconomic management of any direct responsibility for jobs and instead attributing unemployment to regulations, unions, welfare policies and other market distortions.

Japan, Corporate Profits, Kalecki and Living Standards - "Saying that the government's deficit is the non-government's surplus is only a slice of the overall story and really tells us very little about the overall health of the economy. It's more important to understand how domestic investment plays the primary role in how increases in living standards are generated." also btw... -Effects of QE3 -A time of hoarding and inflation fears, 1930s edition -When Banks Were Able to Print Their Own Money, Literally [1,2,3] -Is a revolution in economic thinking under way? [1,2,3] -Judge Posner's Remarkable New Ideas About Taxation, Regulation, and the Constitution [1,2,3] -Robots and Liberalism [1,2,3] -Japan's women hold key to growth

Hint. It's not sugary breakfast cereal.

panaceanot — Thu, 20 Dec 2012 05:20:16 -0800

'If you’re like me, you’ll have asked yourself many times, “Why do toucans have such ridiculously big bills?”' A toucan walks into a 7-11 and asks for a tube of Chapstick. The clerk asks, “Will that be cash or charge?” The toucan replies, “Just put it on my bill!” “Our computer modeling shows that the beak is optimized to an amazing degree for high strength and very little weight,” said Meyers. “It's almost as if the toucan has a deep knowledge of mechanical engineering. Bird beaks are typically either short and thick or long and thin." A discussion of what evolutionary factors might be at play. Bonus! Ugly/cute toucan chicks Credit to comments on both articles for the lame intro joke and the link to baby toucans... this is not a beaking story... can't believe this is the first toucan focused post on metafilter

Wired admires inspired spiders

oulipian — Wed, 19 Dec 2012 11:53:05 -0800

It is common behavior for humans to develop an avatar to present a larger-than-life version of themselves on the web, often as a defense mechanism. For the first time, this activity has been observed in another species.

Nudibranch of the Forest

AceRock — Tue, 11 Dec 2012 12:53:38 -0800

The Translucent Jewel Caterpillar, the Nudibranch of the Forest. Gorgeous caterpillar covered in break-off gumdrops that may help it escape predators. Turns into a bright orange furry moth.

Deciphering the Tools of Nature’s Zombies

Blasdelb — Sun, 09 Dec 2012 07:21:57 -0800

Deciphering the Tools of Nature’s Zombies: The ability of parasites to alter the behaviour of their hosts fascinates both scientists and non-scientists alike. One reason that this topic resonates with so many is that it touches on core philosophical issues such as the existence of free will. If the mind is merely a machine, then it can be controlled by any entity that understands the code and has access to the machinery. This special issue of The Journal of Experimental Biology highlights some of the best-understood examples of parasite-induced changes in host brain and behaviour, encompassing both invertebrate and vertebrate hosts and micro- and macro-parasites. Full issue annotated inside: AN INTRODUCTION:

HOW PERNICIOUS PARASITES TURN VICTIMS INTO ZOMBIES Parasites come in all shapes and forms. From skinny tapeworms that infest intestines to the microscopic infectious agent of malaria (Plasmodium), parasites are usually inconvenient and sometimes lethal. But there is one group of parasites that is particularly pernicious – they are the parasites that hijack their host’s nervous system, turning their victims into zombies. ‘The fact that parasites can so efficiently alter host behaviour is fascinating’, says JEB Editor Michael Dickinson, from the University of Washington, USA, adding, ‘There is something horrifying and wondrous about a tiny “implant” being able to control such a large animal machine’. What is more, it appears that these minute manipulators can have a significant, and often under-appreciated, impact on ecology, physiology and evolution, orchestrating the behaviour of vertebrates and invertebrates alike. ‘Neuroparasitology is a science where science meets science fiction’, Dickinson observes. However, the community tackling the thorny question of how parasites take possession of their hosts by manipulating their nervous systems, and the large-scale implications of these behavioural changes, is tiny. Shelley Adamo – an insect behavioural physiologist from Dalhousie University, Canada – adds that working with parasitic systems is particularly challenging because of the necessity of raising two different organisms in the lab. ...

ALTERATION OF HOST BEHAVIOR

Parasites: evolution’s neurobiologists For millions of years, parasites have altered the behaviour of their hosts. Parasites can affect host behaviour by: (1) interfering with the host’s normal immune–neural communication, (2) secreting substances that directly alter neuronal activity via non-genomic mechanisms and (3) inducing genomic- and/or proteomic-based changes in the brain of the host. Changes in host behaviour are often restricted to particular behaviours, with many other behaviours remaining unaffected. Neuroscientists can produce this degree of selectivity by targeting specific brain areas. Parasites, however, do not selectively attack discrete brain areas. Parasites typically induce a variety of effects in several parts of the brain. Parasitic manipulation of host behaviour evolved within the context of the manipulation of other host physiological systems (especially the immune system) that was required for a parasite’s survival. This starting point, coupled with the fortuitous nature of evolutionary innovation and evolutionary pressures to minimize the costs of parasitic manipulation, likely contributed to the complex and indirect nature of the mechanisms involved in host behavioural control. Because parasites and neuroscientists use different tactics to control behaviour, studying the methods used by parasites can provide novel insights into how nervous systems generate and regulate behaviour. Studying how parasites influence host behaviour will also help us integrate genomic, proteomic and neurophysiological perspectives on behaviour. An overview of parasite-induced behavioral alterations – and some lessons from bats An animal with a parasite is not likely to behave like a similar animal without that parasite. This is a simple enough concept, one that is now widely recognized as true, but if we move beyond that statement, the light that it casts on behavior fades quickly: the world of parasites, hosts and behavior is shadowy, and boundaries are ill-defined. For instance, at first glance, the growing list of altered behaviors tells us very little about how those alterations happen, much less how they evolved. Some cases of parasite-induced behavioral change are truly manipulative, with the parasite standing to benefit from the changed behavior. In other cases, the altered behavior has an almost curative, if not prophylactic, effect; in those cases, the host benefits. This paper will provide an overview of the conflicting (and coinciding) demands on parasite and host, using examples from a wide range of taxa and posing questions for the future. In particular, what does the larger world of animal behavior tell us about how to go about seeking insights – or at least, what not to do? By asking questions about the sensory–perceptual world of hosts, we can identify those associations that hold the greatest promise for neuroethological studies of parasite-induced behavioral alterations, and those studies can, in turn, help guide our understanding of how parasite-induced alterations evolved, and how they are maintained. Parasite manipulation of host personality and behavioural syndromes The past decades have seen mounting evidence that parasites alter their host’s behaviour in ways that benefit transmission, based on differences in the expression of behavioural traits between infected and control individuals, or on significant correlations between trait expression and infection levels. The multidimensional nature of host manipulation has only recently been recognised: parasites do not target single host traits, but instead suites of interrelated traits. Here, I use recent research on animal personality (behavioural differences among individuals consistent across time and situations) and behavioural syndromes (correlations at the population level among distinct behavioural traits, or between the same trait expressed in different contexts) to provide a framework from which simple testable patterns of host behavioural changes can be predicted. Following infection, a manipulative parasite could (i) change the temporal consistency of its host’s behavioural responses, (ii) change the slope of a host reaction norm, i.e. the way host behavioural traits are expressed as a function of an environmental gradient, or (iii) decouple two or more host behavioural traits and/or change the way in which they correlate with each other. Two case studies involving trematode parasites and their freshwater hosts are used to provide empirical illustrations of the above scenarios. These clearly illustrate the full richness of behavioural alterations induced by parasites, and how these effects would go unnoticed using the classical trait-by-trait comparisons of mean values between parasitised and non-parasitised individuals. However, the power of animal personality and behavioural syndromes to inform research on host manipulation by parasites will only be fully realised when underlying mechanisms are elucidated and linked to their phenotypic impacts. Multidimensionality in parasite-induced phenotypic alterations: ultimate versus proximate aspects In most cases, parasites alter more than one dimension in their host phenotype. Although multidimensionality in parasite-induced phenotypic alterations (PIPAs) ^{[FULL TEXT]} seems to be the rule, it has started to be addressed only recently. Here, we critically review some of the problems associated with the definition, quantification and interpretation of multidimensionality in PIPAs. In particular, we confront ultimate and proximate accounts, and evaluate their own limitations. We end up by introducing several suggestions for the development of future research, including some practical guidelines for the quantitative analysis of multidimensionality in PIPAs. Diversity and evolution of bodyguard manipulation Among the different strategies used by parasites to usurp the behaviour of their host, one of the most fascinating is bodyguard manipulation. While all classic examples of bodyguard manipulation involve insect parasitoids, induced protective behaviours have also evolved in other parasite–host systems, typically as specific dimensions of the total manipulation. For instance, parasites may manipulate the host to reduce host mortality during their development or to avoid predation by non-host predators. This type of host manipulation behaviour is rarely described, probably due to the fact that studies have mainly focused on predation enhancement rather than studying all the dimensions of the manipulation. Here, in addition to the classic cases of bodyguard manipulation, we also review these ‘bodyguard dimensions’ and propose extending the current definition of bodyguard manipulation to include the latter. We also discuss different evolutionary scenarios under which such manipulations could have evolved. How much energy should manipulative parasites leave to their hosts to ensure altered behaviours? Although host manipulation is likely to be costly for parasites, we still have a poor understanding of the energetic aspects underlying this strategy. It is traditionally assumed that physiological costs are inevitably associated with mechanisms evolved by parasites to induce the required changes in host behaviours. While most energetic expenditures of parasites relate primarily to bringing about the altered behaviours, manipulative parasites also have to consider the condition of their host during the manipulation. Here, we suggest that because of this trade-off, the energy required to accomplish parasite-induced behaviours may represent a key energetic constraint for parasites. Depending on the energetic expenditures specific to each type of manipulation, parasites should undergo selection to secure resources for their host to allow them to perform manipulated behaviours. What can parasitoid wasps teach us about decision-making in insects? Millions of years of co-evolution have driven parasites to display very complex and exquisite strategies to manipulate the behaviour of their hosts. However, although parasite-induced behavioural manipulation is a widespread phenomenon, the underlying neuronal mechanisms are only now beginning to be deciphered. Here, we review recent advancements in the study of the mechanisms by which parasitoid wasps use chemical warfare to manipulate the behaviour of their insect hosts. We focus on a particular case study in which a parasitoid wasp (the jewel wasp Ampulex compressa) performs a delicate brain surgery on its prey (the American cockroach Periplaneta americana) to take away its motivation to initiate locomotion. Following a brief background account of parasitoid wasps that manipulate host behaviour, we survey specific aspects of the unique effects of the A. compressa venom on the regulation of spontaneous and evoked behaviour in the cockroach host.
(Big awesome post about parasitoid wasps previously: The players in a mutualistic symbiosis: insects, bacteria, viruses, and virulence genes.)
Comparing mechanisms of host manipulation across host and parasite taxa Parasites affect host behavior in several ways. They can alter activity, microhabitats or both. For trophically transmitted parasites (the focus of our study), decreased activity might impair the ability of hosts to respond to final-host predators, and increased activity and altered microhabitat choice might increase contact rates between hosts and final-host predators. In an analysis of trophically transmitted parasites, more parasite groups altered activity than altered microhabitat choice. Parasites that infected vertebrates were more likely to impair the host’s reaction to predators, whereas parasites that infected invertebrates were more likely to increase the host’s contact with predators. The site of infection might affect how parasites manipulate their hosts. For instance, parasites in the central nervous system seem particularly suited to manipulating host behavior. Manipulative parasites commonly occupy the body cavity, muscles and central nervous systems of their hosts. Acanthocephalans in the data set differed from other taxa in that they occurred exclusively in the body cavity of invertebrates. In addition, they were more likely to alter microhabitat choice than activity. Parasites in the body cavity (across parasite types) were more likely to be associated with increased host contact with predators. Parasites can manipulate the host through energetic drain, but most parasites use more sophisticated means. For instance, parasites target four physiological systems that shape behavior in both invertebrates and vertebrates: neural, endocrine, neuromodulatory and immunomodulatory. The interconnections between these systems make it difficult to isolate specific mechanisms of host behavioral manipulation.

NEUROIMMUNOLOGY

Parasite-induced alterations of sensorimotor pathways in gammarids: collateral damage of neuroinflammation? Some larval helminths alter the behavior of their intermediate hosts in ways that favor the predation of infected hosts, thus enhancing trophic transmission. Gammarids (Crustacea: Amphipoda) offer unique advantages for the study of the proximate factors mediating parasite-induced behavioral changes. Indeed, amphipods infected by distantly related worms (acanthocephalans, cestodes and trematodes) encysted in different microhabitats within their hosts (hemocoel, brain) present comparable, chronic, behavioral pathologies. In order to evaluate the potential connection between behavioral disturbances and immune responses in parasitized gammarids, this Review surveys the literature bearing on sensorimotor pathway dysfunctions in infected hosts, on the involvement of the neuromodulator serotonin in altered responses to environmental stimuli, and on systemic and neural innate immunity in arthropods. Hemocyte concentration and phenoloxidase activity associated with melanotic encapsulation are depressed in acanthocephalan-manipulated gammarids. However, other components of the arsenal deployed by crustaceans against pathogens have not yet been investigated in helminth-infected gammarids. Members of the Toll family of receptors, cytokines such as tumor necrosis factors (TNFs), and the free radical nitric oxide are all implicated in neuroimmune responses in crustaceans. Across animal phyla, these molecules and their neuroinflammatory signaling pathways are touted for their dual beneficial and deleterious properties. Thus, it is argued that neuroinflammation might mediate the biochemical events upstream of the serotonergic dysfunction observed in manipulated gammarids – a parsimonious hypothesis that could explain the common behavioral pathology induced by distantly related parasites, both hemocoelian and cerebral. The significance of cerebral toxocariasis: a model system for exploring the link between brain involvement, behaviour and the immune response Toxocara canis is a parasitic nematode that infects canines worldwide, and as a consequence of the widespread environmental dissemination of its ova in host faeces, other abnormal hosts including mice and humans are exposed to infection. In such abnormal or paratenic hosts, the immature third-stage larvae undergo a somatic migration through the organs of the body but fail to reach maturity as adult worms in the intestine. The presence of the migrating larvae contributes to pathology that is dependent upon the intensity of infection and the location of the larvae. A phenomenon of potential public health significance in humans and of ecological significance in mice is that T. canis larvae exhibit neurotrophic behaviour, which results in a greater concentration of parasites in the brain, as infection progresses. Toxocara larval burdens vary between individual outbred mice receiving the same inocula, suggesting a role for immunity in the establishment of cerebral infection. Although the systemic immune response to T. canis has been widely reported, the immune response in the brain has received little attention. Differential cytokine expression and other brain injury-associated biomarkers have been observed in infected versus uninfected outbred and inbred mice. Preliminary data have also suggested a possible link between significant memory impairment and cytokine production associated with T. canis infection. Mice provide a useful, replicable animal model with significant applicability and ease of manipulation. Understanding the cerebral host–parasite relationship may shed some light on the cryptic symptoms of human infection where patients often present with other CNS disorders such as epilepsy and mental retardation. Immune–neural connections: how the immune system’s response to infectious agents influences behavior Humans and animals use the classical five senses of sight, sound, touch, smell and taste to monitor their environment. The very survival of feral animals depends on these sensory perception systems, which is a central theme in scholarly research on comparative aspects of anatomy and physiology. But how do all of us sense and respond to an infection? We cannot see, hear, feel, smell or taste bacterial and viral pathogens, but humans and animals alike are fully aware of symptoms of sickness that are caused by these microbes. Pain, fatigue, altered sleep pattern, anorexia and fever are common symptoms in both sick animals and humans. Many of these physiological changes represent adaptive responses that are considered to promote animal survival, and this constellation of events results in sickness behavior. Infectious agents display a variety of pathogen-associated molecular patterns (PAMPs) that are recognized by pattern recognition receptors (PRRs). These PRR are expressed on both the surface [e.g. Toll-like receptor (TLR)-4] and in the cytoplasm [e.g. nucleotide-binding oligomerization domain (Nod)-like receptors] of cells of the innate immune system, primarily macrophages and dendritic cells. These cells initiate and propagate an inflammatory response by stimulating the synthesis and release of a variety of cytokines. Once an infection has occurred in the periphery, both cytokines and bacterial toxins deliver this information to the brain using both humoral and neuronal routes of communication. For example, binding of PRR can lead to activation of the afferent vagus nerve, which communicates neuronal signals via the lower brain stem (nucleus tractus solitarius) to higher brain centers such as the hypothalamus and amygdala. Blood-borne cytokines initiate a cytokine response from vascular endothelial cells that form the blood–brain barrier (BBB). Cytokines can also reach the brain directly by leakage through the BBB via circumventricular organs or by being synthesized within the brain, thus forming a mirror image of the cytokine milieu in the periphery. Although all cells within the brain are capable of initiating cytokine secretion, microglia have an early response to incoming neuronal and humoral stimuli. Inhibition of proinflammatory cytokines that are induced following bacterial infection blocks the appearance of sickness behaviors. Collectively, these data are consistent with the notion that the immune system communicates with the brain to regulate behavior in a way that is consistent with animal survival.

TOXOPLASMOSIS

Toxoplasma gondii infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour? We examine the role of the protozoan Toxoplasma gondii as a manipulatory parasite and question what role study of infections in its natural intermediate rodent hosts and other secondary hosts, including humans, may elucidate in terms of the epidemiology, evolution and clinical applications of infection. In particular, we focus on the potential association between T. gondii and schizophrenia. We introduce the novel term ‘T. gondii–rat manipulation–schizophrenia model’ and propose how future behavioural research on this model should be performed from a biological, clinical and ethically appropriate perspective. Toxoplasma gondii infection and behaviour – location, location, location? Parasite location has been proposed as an important factor in the behavioural changes observed in rodents infected with the protozoan Toxoplasma gondii. During the chronic stages of infection, encysted parasites are found in the brain but it remains unclear whether the parasite has tropism for specific brain regions. Parasite tissue cysts are found in all brain areas with some, but not all, prior studies reporting higher numbers located in the amygdala and frontal cortex. A stochastic process of parasite location does not, however, seem to explain the distinct and often subtle changes observed in rodent behaviour. One factor that could contribute to the specific changes is increased dopamine production by T. gondii. Recently, it was found that cells encysted with parasites in the brains of experimentally infected rodents have high levels of dopamine and that the parasite encodes a tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of this neurotransmitter. A mechanism is proposed that could explain the behaviour changes due to parasite regulation of dopamine. This could have important implications for T. gondii infections in humans. Parasite-augmented mate choice and reduction in innate fear in rats infected by Toxoplasma gondii Typically, female rats demonstrate clear mate choice. Mate preference is driven by the evolutionary need to choose males with heritable parasite resistance and to prevent the transmission of contagious diseases during mating. Thus, females detect and avoid parasitized males. Over evolutionary time scales, parasite-free males plausibly evolve to advertise their status. This arrangement between males and females is obviously detrimental to parasites, especially for sexually transmitted parasites. Yet Toxoplasma gondii, a sexually transmitted parasite, gets around this obstacle by manipulating mate choice of uninfected females. Males infected with this parasite become more attractive to uninfected females. The ability of T. gondii to not only advantageously alter the behavior and physiology of its host but also secondarily alter the behavior of uninfected females presents a striking example of the ‘extended phenotype’ of parasites. Toxoplasma gondii also abolishes the innate fear response of rats to cat odor; this likely increases parasite transmission through the trophic route. It is plausible that these two manipulations are not two distinct phenotypes, but are rather part of a single pattern built around testosterone-mediated interplay between mate choice, parasitism and predation. Influence of latent Toxoplasma infection on human personality, physiology and morphology: pros and cons of the Toxoplasma–human model in studying the manipulation hypothesis The parasitic protozoan Toxoplasma gondii infects about one-third of the population of developed countries. The life-long presence of dormant stages of this parasite in the brain and muscular tissues of infected humans is usually considered asymptomatic from the clinical point of view. In the past 20 years, research performed mostly on military personnel, university students, pregnant women and blood donors has shown that this ‘asymptomatic’ disease has a large influence on various aspects of human life. Toxoplasma-infected subjects differ from uninfected controls in the personality profile estimated with two versions of Cattell’s 16PF, Cloninger’s TCI and Big Five questionnaires. Most of these differences increase with the length of time since the onset of infection, suggesting that Toxoplasma influences human personality rather than human personality influencing the probability of infection. Toxoplasmosis increases the reaction time of infected subjects, which can explain the increased probability of traffic accidents in infected subjects reported in three retrospective and one very large prospective case-control study. Latent toxoplasmosis is associated with immunosuppression, which might explain the increased probability of giving birth to a boy in Toxoplasma-infected women and also the extremely high prevalence of toxoplasmosis in mothers of children with Down syndrome. Toxoplasma-infected male students are about 3 cm taller than Toxoplasma-free subjects and their faces are rated by women as more masculine and dominant. These differences may be caused by an increased concentration of testosterone. Toxoplasma also appears to be involved in the initiation of more severe forms of schizophrenia. At least 40 studies confirmed an increased prevalence of toxoplasmosis among schizophrenic patients. Toxoplasma-infected schizophrenic patients differ from Toxoplasma-free schizophrenic patients by brain anatomy and by a higher intensity of the positive symptoms of the disease. Finally, five independent studies performed in blood donors, pregnant women and military personnel showed that RhD blood group positivity, especially in RhD heterozygotes, protects infected subjects against various effects of latent toxoplasmosis, such as the prolongation of reaction times, an increased risk of traffic accidents and excessive pregnancy weight gain. The modern human is not a natural host of Toxoplasma. Therefore, it can only be speculated which of the observed effects of latent toxoplasmosis are the result of the manipulation activity of the Toxoplasma aimed to increase the probability of its transmission from a natural intermediate to the definitive host by predation, and which are just side effects of chronic infection.

NEW APPROACHES

Investigating candidate neuromodulatory systems underlying parasitic manipulation: concepts, limitations and prospects Studies addressing the functional basis of parasitic manipulation suggest that alteration of the neuromodulatory system is a common feature of manipulated hosts. Screening of the neuromodulatory system has so far been carried out by performing ethopharmacological analysis, biochemical quantification of neurotransmitters and neuromodulators, and/or immunocytochemistry. Here, we review the advantages and limitations of such approaches through the analysis of case studies. We further address whether the analysis of candidate neuromodulatory systems fits the current view of manipulation as being multidimensional. The benefits in combining ethopharmacology with more recent molecular tools to investigate candidate neuromodulatory pathways is also emphasized. We conclude by discussing the value of a multidisciplinary study of parasitic manipulation, combining evolutionary (parasite transmission), behavioural (syndrome of manipulation) and neuroimmunological approaches. Pathways to understanding the extended phenotype of parasites in their hosts The study of the adaptive manipulation of animal behavior by parasites is entering very exciting times. Collectively the field has moved from its important and instructional natural history phase into proximate-level studies aiming to elucidate the mechanisms by which one organism controls another. Because many cases studies involve cross-kingdom control of behaviour, the findings are sure to be exciting. In this review I examine what possible pathways we can take to understanding the controlling behavior of parasites and how host behavior has become an extended phenotype of the parasites that is often hidden from view. Host–parasite molecular cross-talk during the manipulative process of a host by its parasite Many parasite taxa are able to alter a wide range of phenotypic traits of their hosts in ways that seem to improve the parasite’s chance of completing its life cycle. Host behavioural alterations are classically seen as compelling illustrations of the ‘extended phenotype’ concept, which suggests that parasite genes have phenotype effects on the host. The molecular mechanisms and the host–parasite cross-talk involved during the manipulative process of a host by its parasite are still poorly understood. In this Review, the current knowledge on proximate mechanisms related to the ‘parasite manipulation hypothesis’ is presented. Parasite genome sequences do not themselves provide a full explanation of parasite biology nor of the molecular cross-talk involved in host–parasite associations. Recently, first-generation proteomics tools have been employed to unravel some aspects of the parasite manipulation process (i.e. proximate mechanisms and evolutionary convergence) using certain model arthropod-host–parasite associations. The pioneer proteomics results obtained on the manipulative process are here highlighted, along with the many gaps in our knowledge. Candidate genes and biochemical pathways potentially involved in the parasite manipulation are presented. Finally, taking into account the environmental factors, we suggest new avenues and approaches to further explore and understand the proximate mechanisms used by parasite species to alter phenotypic traits of their hosts.