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November 25, 2008 9:04 PM   Subscribe

"Leaves that crawl".... Assimilated chloroplasts give a species of sea slug its deep green glow; and to keep it, Elysia Chlorotica becomes even a little more plant-like....
posted by Kronos_to_Earth (23 comments total) 13 users marked this as a favorite

 
Free yourself from the chains of middlemanism, and food! Transhuman photosynthesis is the future!
posted by finite at 9:32 PM on November 25, 2008


Could we even run on photosynthesis alone? Don't we need a higher output energy source or can photosynthesis really power a human in real time, and not in like, bursts after long periods of charging (so to speak)?
posted by TwelveTwo at 10:09 PM on November 25, 2008


According to this website the sun sends down about 164 Watts per square metre. We supposedly have about 2 metres of skin surface area.

A person with 2 metres of skin surface area probably burns about 2400 kilocalories a day, which is about 420000 joules an hour, which is about 115 watts.

Assuming we could only get about 1/3 of our skin covered by sunlight, then if we had perfect photosynthesis - i.e., we got every last joule out of sunlight we could, then yes. We could just about do it.

Otherwise, since we can't do such a perfect conversion of sunlight, we would have to scale our daily energy expenditure in accordance with the efficiency of our photosynthesis.

Anyway, that was all in my head, so hopefully I didn't screw up somewhere.
posted by Alex404 at 10:36 PM on November 25, 2008 [5 favorites]


Sweet! Let's get to work.
posted by TwelveTwo at 10:44 PM on November 25, 2008


Could we even run on photosynthesis alone? Don't we need a higher output energy source or can photosynthesis really power a human in real time, and not in like, bursts after long periods of charging (so to speak)?
posted by TwelveTwo at 1:09 AM on November 26 [+] [!]
.

Oh it's worse than that. If you want to evolve sentience you're going to be an omnivore with a mild preference for meat (higher energy/protein density), period.
posted by Ryvar at 10:56 PM on November 25, 2008


*not intended to imply that vegans are non-sentient. Just that vegan rhesus monkeys aren't going to be bridging the gap anytime soon.
posted by Ryvar at 10:59 PM on November 25, 2008


wow. The language itself is marvelous:

"The sacoglossan sea slug [certainly this must be the name of an extraterrestrial relative of Dr. Pangloss], Elysia crispata [a fried dessert in Greek paradise], sequesters chloroplasts [so poetic] from its algal food source [sounds like something in the Jabberwocky] within specialized cells lining the digestive diverticulum [a diverting tickle?]. These stolen chloroplasts photosynthesize within the slug cell cytoplasm as long as four months--one of the longest kleptoplastic [whoa stolen fake orgasms? no that would be kleptogasmic] associations known"

What an exciting discovery. Here's what the scientist, Mary E. Rumpho, looks like. A video interview with her.

Some icing on the cake: "In addition, we are exploring the possibility that the sea slug produces anti-cancer metabolites as an anti-predator defense mechanism."
posted by nickyskye at 11:09 PM on November 25, 2008 [3 favorites]


Woah, this is so cool.

The New Scientist article says:

Other animals are able to harness sunlight after eating plants, says Rumpho, but this is only because they acquire entire plant cells, which is very different to transforming an animal cell into a solar-powered plant-animal hybrid.


Anyone know what these other animals are?
posted by overglow at 11:46 PM on November 25, 2008 [1 favorite]


Anyone know what these other animals are?

May I present the 44th President of the United States? I tell you, the man has thought of everything.
posted by maxwelton at 12:42 AM on November 26, 2008


So, it's not easy being green.
posted by Phanx at 1:27 AM on November 26, 2008 [1 favorite]


Anyone know what these other animals are?

Well, some flatworms (Convoluta roscoffensis) host entire algae and some jellyfish have a similar tactic, eg Cassiopea andromeda - the Upside Down Jelly fish, which has dinotlagellate endosymbionts in its scyphomedusae (ooh!) and whose reverse habit apparently stems from the need to keep its photosynthesising bits near the sun. Sea anemones like anthopleura also go in for symbiotic algae.

In fact this sort of recklessly opportunistic cohabitation appears to be rife in some quarters, but I believe the authorities have said they are powerless to act.
posted by Phanx at 1:58 AM on November 26, 2008 [2 favorites]


Yes, cnidarians, I am looking at you.
posted by Phanx at 2:58 AM on November 26, 2008


Previously

If you want to evolve sentience you're going to be an omnivore with a mild preference for meat (higher energy/protein density), period.

Meat has a high protein density but the highest energy density is from fats. Which many plants have in seeds, which is where we get corn oil, coconut oil, olive oil, etc.

Could we even run on photosynthesis alone?

Obviously we'd need some bioengineering to make this work anyway--implanting the chloroplasts at the very least. So while we're at it, we could bump up our efficiency a little, change our behavior a little (more sun-seeking, etc) and maybe increase our surface area and/or sun-pointed cross section.
posted by DU at 5:01 AM on November 26, 2008 [1 favorite]


If you want to evolve sentience you're going to be an omnivore with a mild preference for meat (higher energy/protein density), period.

Meat has a high protein density but the highest energy density is from fats. Which many plants have in seeds, which is where we get corn oil, coconut oil, olive oil, etc.


DU, you're right of course. The point Ryvar missed is that it's not just energy density, but a diverse and rich source of proteins that is needed to fuel brain growth. Seeds aren't enough for that.

Why Ryvar brought up the point about evolving sentience is beyond me, though. I don't particularly feel the need to evolve any more of it, do you?
posted by IAmBroom at 5:39 AM on November 26, 2008


I don't get why I have to eat meat to get these proteins (evolutionarily speaking I mean--I'm not a vegetarian). The proteins are only found in the bodies of animals, not plants, I get that. But that just pushes the problem down a level. Where did the proteins in the bodies of those animals come from? They made them from plant inputs, right? So....if my body needs those proteins to build a brain, why not just make them from plant inputs and skip the middleman? (Modulo every step of the chain being evolutionarily blah blah blah)
posted by DU at 5:48 AM on November 26, 2008


I guess this isn't too surprising. Many similar sea slugs eat jellyfish polyps and absorb the nematocysts (stinging cells). Without digesting the stinging cells, they redeposit them into the serrata on their back and use the cells as their own defensive mechanism.
posted by cyclopticgaze at 5:49 AM on November 26, 2008


You had me at "kleptoplasts".
posted by Mister_A at 7:39 AM on November 26, 2008


Yes, cnidarians, I am looking at you.

I think it's OK....
posted by Kronos_to_Earth at 7:53 AM on November 26, 2008


It's a beautiful creature, eh? And, I would totally eat it.
posted by not_on_display at 9:32 AM on November 26, 2008


/derail
stolen fake orgasms is actually kleptoplasticgasmic
posted by nickyskye at 9:56 AM on November 26, 2008


This is fantastic. Now just please let those algal genes be as compatible with my mammalian genome as they are with yonder mollusc.

I love the site in the 3rd link. They have really done their homework.
posted by eritain at 11:22 AM on November 26, 2008


DU, I guess that the point in eating meat/animals to get those essential amino acids/oils/fats for brain growth is that the animals have done all the tedious finding, consumption and, in a lot of cases anabolic conversion of huge amaounts of plant matter for you already.

Think of the tasty animals as walking resource concentrators
posted by JustAsItSounds at 4:09 PM on November 26, 2008


DU: I don't have the answer to your question, but I can offer some information in the hope that someone more knowledgeable will fill in the blanks. I hope I'm not being a pedant, but you have misused some biological terms and I think it'd be helpful to set them straight:

1) Amino acids are the building blocks of protein (and the sequence of the amino acid determines the structure of the protein, and the structure of the protein determines its function). It only takes about two dozen different amino acids to form all of the proteins needed by life on our planet. Many bacteria and plants are able to synthesize all their amino acids from other basic molecular building blocks. Us humans are only able to make some of our needed amino acids and forced to rely on consuming other organisms, both plant (yes plants do contain protein) and animal, to provide our protein building blocks. The amino acids that humans cannot produce are known as essential amino acids, meaning we must obtain these building blocks from the things we eat.

2) Your DNA carries instructions to build the all proteins you need to live*. Any animal or plant protein you consume will be broken down to its constituent amino acids. Your metabolic pathways break down incoming protein to the basic amino acids then build them back up into the proteins as you need them. Because proteins vary slightly between species, you cannot use another organism's protein without first breaking it down to its building blocks then putting it back together, your body would reject any foreign protein as an invader. *Yes, I'm probably over-simplifying: there are all sorts of bacteria in your gut that help you break down food, plus without yeasts there would be no bread or beer and life wouldn't be worth living...

3) The NewScientist article points out that this sea slug does not have genes that build the proteins that are required to maintain its stolen chloroplasts. That's the crazy thing going on there, the sea slugs aren't just stealing an organelle but also taking the genes to maintain them. It's be like if you ate a chicken then you'd be able to grow feathers -- that is to say by consuming chicken flesh you'd be able to express chicken genes to produce feathers. These sea slugs have a method for incorporating the protein producing genes of their prey into their own metabolic pathways. That's the exciting thing going on here.

But I'm at the edge of my knowledge domain, so it'd be super if a molecular biologist could point to reasons why humans can't synthesize all on their amino acids and provide some conjecture on why we have lost this ability.
posted by peeedro at 9:20 PM on November 26, 2008


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