Chelycypraea testudinaria, Marshall Islands

Chelycypraea testudinaria (Linnaeus, 1758)
Tortoise cowry, 77-132mm

Chelycypraea testudinaria grows the longest of the Marshall Islands cowries. It lives in numerous locations, but living animals are most often found beneath large rocks on tops of large, flat-topped pinnacles (such as those at Gea Pass and Kwadak Island) or in shallower surge channel caves and on the knee of the seaward reef dropoff. Depths for most specimens range from 0-16m. The smallest specimens live under large boulders at about 8-13m on the hard flat reef on the windward seaward reef. Specimens are also occasionally found under rocks or hiding in crevices intertidally. Empty shells are seen far more frequently than living animals. Dead shells, often occupied by the hermit crab Dardanus guttatus, are common in seaward reef surge channels and along some lagoon interisland reefs, such as that between Bigej and Meck Islands. Chelycypraea testudinaria is distributed widely in the Indo-Pacific with the apparent exception of the Hawaiian Islands and Western Australia.

This cowry's mantle is brownish gray with slightly irregular lighter and darker longitudinal lines. Simple spiked papillae of the same brownish gray color but with lighter tips are scattered over the mantle. The mantle color almost but does not quite obscure the color pattern of the shell beneath it. Anterior tentacles are dark gray, nearly black. We once found a specimen that appeared to be empty but after bringing it home, discovered the animal was still inside. We dropped it into an aquarium, where it took several days before the animal peeked out of its shell. Turned out one anterior tentacle and the eye at its base were gone, amputated probably by a predator who left the shell, possibly as we approached. We kept the shell for some months in the aquarium, where it fully regenerated its lost tentacle and eyestalk, then released it back on the reef.