| MadSci Network: General Biology |
Hi Richard,
What an interesting question! I'm not aware of any crab that builds any structures using composite materials (crabs, like all arthropods, have their own exoskeleton that functions as a shell and is secreted by the epidermis), but there is a polychaete tubeworm that lives along certain shores here in California, that might suit your purposes.
This worm, Phragmatopoma californica, builds a tube out of sand grains, which
it cements together around a lining of chitinous material. The worms' tubes form large
aggregations in the intertidal along rocky shores that have appropriately sized sand grains.
Here's a photo of a clump of Phragmatopoma that I've been keeping in the lab:
Each tube is about 5 mm wide, and up to 10 cm long, even though the worms themselves are only about 3 cm long. The worms build their tubes next to each other, and all of the tubes' openings face the same direction:
The worms are pretty choosy when it comes to selecting sand grains for the tubes. Generally, only sand grains in a particular size range are used, while grains that are too large or too small are discarded. Here's a close-up photo that I took of a single tube from which the worm has been removed, so you can see for yourself the similarity in grain sizes:
I hope this is the kind of example you were looking for. If you wish to use any of these photographs, please notify me via the MadSci website. I think that if you were to submit an e-mail to webadmin@www.madsci.org, it would find its way to me.
Allison J. Gong
Mad Scientist
References:
Ricketts, E.F.; Calvin, J.; and Hedgpeth, J.W. 1985. Between Pacific Tides, 5th edition. Stanford University Press.
Morris, R.H.; Abbott, D.P.; and Haderlie, E.C. 1980. Intertidal Invertebrates of
California. Stanford University Press.
Try the links in the MadSci Library for more information on General Biology.