Those who live in glass houses

May 12, 2017 12:06 AM

Glass sponges, or hexactinellida, are uncommon sponges with siliceous skeletons found in deep waters all over the world and renowned for their intricately beautiful forms. They are among the oldest animals on Earth, and individuals can be literally unbelievably long-lived. Although not composed of actual glass, the spicules that form their characteristic skeletons are made of silica, used to produce glass and optical fiber. Starting today, you can watch livestreamed deep research off the coast of British Columbia into glass sponges living there and the ecosystem supporting them.
posted by byanyothername (8 comments total)

From an article linked by the Scientific American article:

Unlike other sponges, hexactinellids form spicules exclusively inside their cells.

So, how can a sponge make giant spicules inside cells? The hexactinellid sponges are said to display the syconoid pattern of organization. To put it mildly, this understates the weirdness of the hexactinellid body plan. In fact, hexactinellids have perhaps the strangest of all animal bodies. Most of the tissue consists of a single giant, multinucleate syncytium. This syncytium forms both "the inner and outer layers of the sponge and is joined by cytoplasmic bridges to uninucleate cellular regions." Leys et al. (2006).

That is, a hexactinellid can make giant spicules because its body is composed largely of one giant cell.

That is wonderfully wonderful. IIRC, fruit fly eggs briefly develop into a multinucleate syncytium, and some slime molds live that way, but none of those are building ten-foot-tall glass(ish) houses.
posted by clawsoon at 12:40 AM on May 12, 2017 [3 favorites]

[Or ten-foot-tall glass-ish "roots", anyway.]

Do the new results from Antarctica about how fast they're growing undermine the previous estimates of how long-lived they can get, since the longevity estimates were based on their previously observed incredibly slow rate of growth? Or is something else going on?

Great post, BTW.
posted by clawsoon at 1:02 AM on May 12, 2017

Being around for many hundreds of millions of years, living up to thousands of years. Seems like they might have about the same number of generations as humans.
posted by StickyCarpet at 3:22 AM on May 12, 2017

The factoid about the shrimp living trapped inside the Venus' flower basket was interesting; more about them here, including a picture. Apparently they must be pretty camera-shy, as there don't seem to be very many photos of the shrimp on the internet.
posted by TedW at 5:58 AM on May 12, 2017 [2 favorites]

I heard about these on the CBC yesterday and was excited to see the photos of what they look like! They're beautiful and amazing. Great post!
posted by hurdy gurdy girl at 8:29 AM on May 12, 2017

I like the image with the crab--it's as if he's at a museum, observing a piece of sculpture.
posted by praemunire at 8:34 AM on May 12, 2017

These things are getting more interesting the more I look into them. Here is a scientist saying that they use their fibre-optic fibres in conjunction with bioluminescent bacteria to light up like a Christmas tree.
posted by clawsoon at 12:01 PM on May 12, 2017

Fun fact: my dad co-authored the series of three papers in 1983 which split the phylum Porifera (sponges) into two sub-phyla Symplasma (Hexactinellida -- glass sponges) and Cellularia (all the others), which was a fairly deep-level re-organization in the world of taxonomy.

"Two new subphyla are proposed and defined, the Symplasma to include the single class Hexactinellida, and the Cellularia to include all other extant sponges of the classes Calcarea, Demospongiae and Sclerospongiae."
posted by Rumple at 1:45 PM on May 13, 2017 [2 favorites]