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Published online 16 November 2009 | Nature | doi:10.1038/news.2009.1088
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How the sponge stays slim
One species' rapid cell shedding explains its huge carbon-catching capacity.
Biologists have discovered how a reef-dwelling species of sponge can filter enormous amounts of carbon without growing in size.
The sponge Halisarca caerulea can absorb up to two-thirds of its own weight in carbon each day by shedding cells at a rapid rate, according to research by Jasper De Goeij at the Royal Netherlands Institute for Sea Research in Texel, the Netherlands, and his colleagues.
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Could the shed cells be reproductively competent?
Cnidarians have very flexible cells – specialized, but apparently not permanently differentiated. Jellyfish can reproduce by polyp defection, and hydra can regenerate amazingly. Since sponges are also Precambrian, they may have similarly flexible cells.
In that case, the shedding of cells could be an act of reproduction, not just dumping toxins.
If Precambrian cells don't differentiate, then they may not be a very good model for cancer or regeneration in higher animals. (I suspect epigenetics-on-command is the differentiation mechanism.)
I have a paper in press on the conjecture that cellular differentiation was the final trigger for the Cambrian Explosion. Email me at cphoenix at gmail dot com for a copy.