Living Seashells: Egg Cowries

Overview

This issue features three colourful marine gastropod molluscs from the family Ovulidae, commonly called false cowries or ovulids. Approximately 264 species of ovulids are found worldwide, mainly in the tropical and sub-tropical Indo-West Pacific region. The ovulids depicted on the stamps have egg-like shaped shells and are most readily distinguished by their very differently coloured animals.

Ovulids are carnivorous and parasitic, living and feeding on various types of soft corals and sea fans or gorgonians, using their radula, a rasping tongue-like organ, to consume the soft tissue. The snail spends its life anchored to the host by a long, narrow foot. The smooth, shiny shells of ovulids are usually white or pink and vary from pear or egg-shaped to narrow and elongate. In living ovulids, a colourful mantle flap covers the shell, the colour patterns of which may closely resemble the host species. Along with noxious chemicals stored in the skin, this camouflage helps protect the snail from fish predation. When not camouflaged, as is the case with the three species here, the distinctive patterns advertise that the snail is toxic to predators.

The small egg cowries depicted on the stamps were all photographed by Brian R Mayes in the subtropical waters of Nelson Bay, New South Wales.

Technical specifications