Ovula ovum
Glossy white oval shell with a jet-black mantle, most often spotted on reefs in Zanzibar, the Visayas and KwaZulu-Natal year-round.
A smooth, glossy white oval shell about 7 cm long is the giveaway, but you will usually see it wrapped in a jet-black or dark brown mantle that only pulls back to reveal the porcelain-white shell underneath when disturbed. The body is egg-shaped with no obvious markings beyond that stark black-and-white contrast, and it sits fully exposed on top of soft corals rather than tucked into crevices. There is no meaningful colour difference between individuals, so any egg-shaped cowrie with a black mantle on a soft coral is almost certainly this species.
Look for it grazing slowly across the surface of soft corals and gorgonians, often in full view during both day and night dives since it has little reason to hide. It reacts to a close light or a diver's hand by retracting its mantle to expose the bare white shell, which is a useful trick for getting a clean ID shot. Most sightings are of single animals moving unhurriedly over their host coral rather than in groups.
It feeds directly on the soft coral polyps it crawls over, and its black mantle is thought to help camouflage the otherwise conspicuous white shell against the coral's tissue while it grazes.
No clear season shows up in the sighting data, and its comfort range of roughly 23 to 30 C covers most tropical reef conditions year-round, so it is a fair bet on any dive regardless of month.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged on reefs in Zanzibar (Tanzania), the Visayas in the Philippines, and KwaZulu-Natal in South Africa, with strong numbers also out of Diani in Kenya and Nusa Tenggara in Indonesia. It turns up widely across the Philippines, Australia (both New South Wales and Queensland) and Taiwan too, so it is a fair bet on almost any Indo-Pacific soft coral reef within its depth range.
Mapping where Common Egg Cowrie is logged…
It is most consistently logged in Zanzibar, Tanzania and the Visayas in the Philippines, with strong sightings also in KwaZulu-Natal, South Africa and Diani, Kenya. It is widespread across Indo-Pacific reefs generally, including Indonesia, Australia and Taiwan.
There is no strong seasonal pattern in sightings, and it tolerates a wide temperature range from about 23 to 30 C, so divers spot it on tropical reefs throughout the year.
Look for an egg-shaped shell around 7 cm long, glossy white, usually covered by a black or dark brown mantle as it grazes over soft coral. Touch or light disturbance makes it retract the mantle, revealing the smooth white shell fully.
They reach around 7 cm in shell length, making them one of the larger cowrie-family molluscs divers encounter on Indo-Pacific reefs.
Its dark mantle is thought to camouflage an otherwise bright white shell while it feeds directly on the soft coral polyps it crawls across, blending in with the coral's own colour.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Warty Egg Cowrie
87 sites
