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Checkerboard Helmet Shell Phalium areola
Ranging from Africa across to Samoa and north to at least the Philippines the Checkerboard Helmet Shell Phalium areola is easy to identify and dead shells are seen on a regular basis; very commonly displayed in shell shops.
However, as they live in sandy areas and only come to the surface when hunting, mating and laying eggs (mostly at night), few divers are familiar with live ones. Although they do have eyes these are merely light receptors and have no focussing functions. The Checkerboard Helmet Shell animal lives in a world of chemoreception where every part per millionth of a chemical smell carried along by the currents transmits a signal giving the mollusc all the environmental information it requires to live.
A hungry helmet shell comes up out of the sand at night. To find its prey it crawls along on the sand surface with its breathing siphon pointing into the current to pick up any chemical signal from the exhaled water from the Sea Urchins it feeds on. Some hunt sand dwelling Heart Urchins and others hunt regular Sea Urchins living along the edges of reefs.
Whenever a Helmet Shell gets close to a Heart Urchin, the urchin senses danger and literally jumps up out of the sand and sets off at speed. However, the helmet shell is also very quick and immediately produces voluminous amounts of thick mucus which it proceeds to dump on the urchin. The mucus glues up the heart urchins mobile walking spines and slows it down. Once trapped in this sticky substance the Heart Urchin is doomed. The Helmet Shell turns it over and proceeds to eat out its insides by inserting its proboscis into the Heart Urchin's mouth.
The Checkerboard Helmet Shell Phalium areola powering along at night in search of prey. (Anilao, Batangas, Philippines).
(Photo Neville Coleman)
With its Heart Urchin prey Maretia planulata completely at its mercy the Checkerboard Helmet Shell animal virtually eats it alive, slowly rasping out the urchins insides with its radula-tipped proboscis.
(Photo Neville Coleman)