Boring clam (Tridacna crocea), also known as the crocus clam, crocea clam or saffron-coloured clam. The colours come from symbiotic zooxanthellae dinoflagellates in the clam's tissues. Recent research confirms that the foot of this bivalve contains a molecular pump which is able to make the surface of the foot acidic, thereby facilitating the ability to bore into solid coral rock. Photographed in Indonesia.