Abstract.The distribution ofIbla cumingiDARWIN on different types of hard substrata along 30 km of coast in the Gulf of Elat was studied.I. cumingiwas found among and underneathTetraclita squamosa rufotincta, in oyster beds, underneath slabs of beachrock, and in fissures in igneous rocks. In theTetraclitabelt,I. cumingiis most frequent in empty shells of deadTetraclitawhile in the oyster bed it is common inside the meshwork made by the oysters. The distribution is regarded as clustered distribution. The density and size of the clusters ofI. cumingiis determined by the available sheltered space within the midlittoral zone. The form of the habitat determines the shape of the animals. Those found in the oyster bed and fissures are usually longer than those found in theTetraclitabelt due to the depth of the fissures or to the bigger spaces within the oyster bed.I. cumingiis orientated so that the capitulum with the cirri is projecting towards the open water, and the water current. It is concluded thatI. cumingican withstand the physical stress encountered in a tropical intertidal zone, but that the distribution pattern is caused by predation.
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