"If we and the rest of the backboned animals were to disappear overnight, the rest of the world would get on pretty well. But if the invertebrates were to disappear, the land's ecosystems would collapse."
David Attenborough

Tuesday, December 7, 2010

Mollusc Giants- Giant Clams are, well, GIANT!

In the first in this series I thought I'd opt for a beast which is often (unfairly) overlooked when considering the larger invertebrates; the Giant Clam Tridacna gigas.
Its main disadvantage in the wildlife popularity stakes are its general bivalve-y-ness. It has no front or back, no eyes, no face. I personally think that makes bivalves especially intriguing- we really struggle to, er, walk a mile in their shoes as it were. Its just too damn hard to imagine life as a metre long 200kg shelled marine mollusc.
They are deeply weird, but I like that.
They have florid mantle tissue which they extrude from their shells in their daily doings- some of those funky colours are actually symbiotic zooxanthellae living in the clams tissue photosynthesising goodies in exchange for basic nutrients and a home.
They are huge and long lived- they embed in coral but can live for over 100 years in which time the reef can grow around them so that they are completely 'bricked-in' to the coral structure with only the lips of their shell protruding.
Like all bivalves they have an excellent and exotic life history which I will perhaps cover in more depth in future posts.
Giant clams were once common throughout the Indo-pacific coral zone but over hunting and reef decay has taken its toll so now they are unfortunately scarce. I was lucky to encounter a few while diving in Australia's Great Barrier Reef years back. An unforgettable mollusc, and a worthy animal to kick off Mollusc POWs 'Mollusc Giants' series.

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