>> 2.  Why are spines and flutes found primarily on those bivalves that
>> are LEAST likely to be swallowed (sessile types like Spondylus,
>> massive types like Tridacna)?
>--It might be tough to find the right spots to hold a clam closed with
>--lots of spines sticking out. (See my description some time back about
>--how lobsters 'strangle' bivalves.) As for Tridacna, show me its
>--natural predator and I'll try to walk on water getting away from it!
 
 
The "use" of sculpture may change during the growth of the animal. The
scales of adult Tridacna may be useless, but may have been very important to
a 1/2 inch juvenile. Adult scales may simply be a holdover from juvenile ones.
 
We shouldn't write off all spines as being stick-in-the-mouth defenses
against fishes. If you look at a lot of the cemented bivalves (Spondylus,
Chama, Crassadoma, Ostraea, etc), they often have spines or scales. It has
been suggested that these surfaces collect algae and junk, camouflaging the
animal. I doubt it, because I don't think their predators locate them by
sight - they probably "smell/taste" them. I think the camouflage is probably
coincidental with the real purpose of the spines - to keep drilling
gastropods at bay. Important if you're not going anywhere for a while.
 
*  G Thomas Watters               *
*  Ohio Biological Survey &       *
*  Aquatic Ecology Laboratory     *
*  Ohio State University          *
*  1315 Kinnear Rd.               *
*  Columbus, OH 43212 USA         *
*  v:614-292-6170 f:614-292-0181  *
 
"The world is my oyster, except for months with an "R" in them" - Firesign
Theater