Postcard from the Reef – The Horn of Urchin Death

Horned helmet snails feed on sea urchins. The snails are easy to spot once you know what to look for, a shape in the sand. The snail may appear like an abandoned shell on first examination, the top covered with algae. It is the size that is surprising, these snails are huge, the shell well over a foot long and almost as much in diameter.

If an urchin wanders by this snail comes to life, heaving itself out of the sand and moving towards its prey. The large foot appears, lifting the ponderous mass off the ground. A pair of tentacles with small black eyes on the sides appear, sweeping about to search for prey. Once the urchin is located the reaction is surprisingly swift, the snail heaves forward to engulf the hapless urchin.

Horned Helmet Snail
Horned helmet snail (Cassis cornuta) pouncing on a collector urchin (Tripneustes gratilla)

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on the island of Hawaiʻi.

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