Arestorides argus, Marshall Islands

Arestorides argus (Linnaeus, 1758)
Eyed cowry, 49-100mm

Arestorides argus has an unmistakable pattern. These cowries live in a variety of locations throughout the atoll, but are most often found on lagoon pinnacles (such as R-Buoy and Marita Shoals), on the oceanside in surge channel caves and on the slope, and along some interisland reefs such as that between Bigej and Meck Islands. By day the shells live beneath large dead coral rocks, buried several layers down in dead table coral rubble, or well back in dark caves and crevices. At night, they graze on walls and ceilings of small caves or rocky surfaces. We have seen them as shallow as about 5m and as deep as at least 40m. Living animals are infrequently seen, but empty shells in good condition can be found on surge channel floors and along the edge of interisland reefs. Oceanside specimens average larger than those from lagoon pinnacles, and the ones along Bigej-Meck reef seem to be the smallest of all. The name argus refers to the circular “eyes” covering the shell. This species ranges across the Indo-Pacific with the exception of Hawaii and Eastern Australia. The subspecies found in most of the Pacific is Arestorides argus argus.