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.