I'm writing about sea cucumbers. They look like a sort of tube, or a dog turd, or a fat caterpillar. They live in the sea and are an animal, despite the name. In particular, I'm writing about the way a sea cucumber can turn itself almost liquid, ooze through a crack, then solidify the other side so that it can't be prised out. Cool, eh?
I found out about the sea cucumber trick on WebEcoist, which is not a specialist zoology site. It says this about the SC trick:
The sea cucumber can literally take on different body states – from hard to liquid – in order to defend itself. From wikipedia: “Like other echinoderms the cuke has a type of collagen in its skin capable of excreting or absorbing more water effectively changing from a ‘liquid’ to a ‘solid.’ They can turn their bodies into mush, climb through small cracks and then solidify into small lumps so that they cannot be extracted.”
It cites Wikipedia as its source, so off to Wikipedia.... but unfortunately this links to the page on antipredator adaptation which doesn't talk about the liquifying of sea cucumbers. The page on sea cucumbers, however, does:
A remarkable feature of these animals is the catch collagen that forms their body wall. This can be loosened and tightened at will, and if the animal wants to squeeze through a small gap, it can essentially liquefy its body and pour into the space. To keep itself safe in these crevices and cracks, the sea cucumber will hook up all its collagen fibres to make its body firm again.
Now that's not quite the same thing, is it? Hooking of collagen fibres is not the same thing as absorbing or losing water. So off to the first source Wikipedia cites for this info - it's an article in English, apparently in a French journal, but its website is in German. And it's moved. So... follow the link to another German website, which is not looking promising as this the University of Gottingen and the journal was supposed to be from the Université de Bourgogne. Searching finds nothing related. Googling the article title gives the same broken link. Move on...
Second source cited by Wikipedia is a book. But a book that is not in Cambridge University Library.
Back to Google, with sea cucumber and catch collagen, and thence to an advanced aquarists' site which says:
they have a compound in their skin called catch collagen - this tissue is under neurological control and is capable of changing from a 'liquid' to a 'solid' form very quickly (Brusca and Brusca 1990; Motokawa 1984a; Motokawa 1984b; Ruppert and Barnes 1994). This is one of the coolest things about echinoderms in general, and is one of the reasons that this group has been so successful. The ability of the catch collagen to change from liquid to solid form at will is how sea cucumbers manage to get themselves into such tiny holes in the live rock structure - they are able to ‘goopify’ their bodies (for lack of a better description), literally pour themselves into the hole they have chosen, and then solidify their skin to prevent anything from being able to remove them (Motokawa 1984a; Motokawa 1984b).
Real references - good:
Motokawa, T. 1984a. Catch connective tissue: the connective tissue with adjustable mechanical properties. Pp. 69-73 in B. F. Keegan and B. D. S. O'Connor, eds. Proceedings of the Fifth International Echinoderm Conference. Balkema, Rotterdam, NL.
Motokawa, T. 1984b. The viscosity change of the body-wall dermis of the sea cucumber Stichopus japonicus caused by mechanical and chemical stimulation. Comp. Biochem. Physiol. A, 77A:419-423.
But they're not in CUL either. Back to Google:
The compound is made of a material called 'catch collagen' which can change from liquid to solid when neurologically triggered. It does this so can squeeze into small spaces and then harden again. Another defense is they "pee" out all the water in their system and shrink into a small, hard rock.
So what is actually going on in this animal? By happy good fortune, I have a bint doing zoology at Oxford, with a tutor who is a world expert on marine thingies like these. Last port of call - Facebook.
But it wasn't last, because people are not always on Facebook when you need them to be. More fiddling around on Google reveals that 'catch collagen' is more properly called 'mutable collagenous tissue' or MCT. And now we get somewhere: there is an article in The Journal of Experimental Biology, 2002, that describes research into MCT in echinoderms. Current thinking, it appears, is that the sea cucumber controls the connections between fibrils of collagen by releasing chemicals into its tissues:
mutable collagenous structures consist of discontinuous collagen ﬁbrils organised into bundles (ﬁbres) by an elastomeric network of ﬁbrillin microﬁbrils and interconnected by a stress-transfer matrix consisting partly of stiparin, a glycoprotein that binds to and aggregates the ﬁbril…[etc]
There are chemicals that can prevent bridges forming between fibrils, so the creature loses its structure entirely, becoming flobbly. The chemical release is under neurological control. Hurray! Got there! (And Wikipedia was right this time, saying it 'hook[s] up its collagen fibres'.)
What will all this amount to? About 30 words in a book for reluctant readers on animals that do amazing things. But - and here's the real point - it is AT LEAST as important to do the research properly for a children's book as for an adult book. And although the book won't mention collagen or fibrils or MCT or any of that, at least it will NOT now say that the sea cucumber sucks water into its cells to make itself more liquid.
And, to the next person who asks, that is why I am paid £2 a word for a book like this. It took an hour's research to prevent me writing 'sea cucumbers absorb water to make their bodies gloopy' and write 'sea cucumbers use chemicals to change their bodies to gloop.' An hour well spent.
Disclaimer: This doesn't mean there are no errors in my books. But I do work hard to avoid them!