Researches on the Coast of Somalia. The Shore and the Dune of Sar Uanle

SUMMARYOcypode ryderi Kingsley (Crustacea Brachyura) from South Somalia dig Y-shaped or unbranched (slightly arched) burrows. The secondary branch of the Y usually does not lead to the surface. Female O. ryderi dig burrows at higher levels than males, while no relationship exists between sex and shape, nor between shape and distance from the sea. A sand pile is usually present just near the entrance of the male burrow. Burrows never inter-communicate, they are oriented roughly seawards and have the sand pile almost in front of the entrance. Sand is always carried out with the minor claw and the two adjacent walking legs. The crab always exits from the burrow leading with the major claw free of sand. The excavated sand (scattered or heaped in a pile) is periodically flattened by a typical trampling movement. The burrow structure and digging behaviour of O. ryderi were compared to those of known Ocypode species and other digging crabs. The shapes of the burrows of a few O. cordimana Desmarest, O. ceratophthalmus (Pallas) and other digging crabs were also recorded.