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The use of the pleopods was investigated in two species of Diogenid hermit crabs, Dardanus arrosor and D. calidus. A transparent glass shell was used to observe the movements of the pleopods in hermit crabs. The movements consisted of periodic, irregular beating, which generated an irregular flow of the water within the shell. A strong, regular beating movement was elicited when there was detritus or faeces in the shell, as was occupation of a new shell. Injection of water with a low oxygen concentration into the shell failed to induce any variation in the pleopod beating frequency (PBF), while the injection of water with a high CO2 concentration induced a sudden PBF increase. When pH was varied and CO2 concentration held at normal atmospheric level, there was a change in PBF. However, CO2 variation alone, at constant pH, did not trigger any visible reaction. This suggests that there is a receptor for pH, which acts independently of the CO2 concentration. The function of males hermit crabs pleopods has always been obscure. However, at least in Dardanus, they are actively involved in water circulation within the shell for shell-cleaning and probably for ventilation. [ABSTRACT FROM AUTHOR]

The ecology and taxonomy of an interesting species of tree-living freshwater crab from the East Usambara mountains, Tanzania, and from the Shimba Hills, Kenya, East Africa is described. This phytotelmic decapod crustacean belongs to a new species of potamonautid freshwater crab in the genus Potamonautes MacLeay, 1838, which is described. This is one of only a few reports of the phenomenon of the use of water-filled tree holes by any species of true freshwater crab. [ABSTRACT FROM AUTHOR]

The article offers information about the first record of the land crab, Discoplax rotunda, from East Africa. It tries to inquire the geographical distribution of this specie. According to authors, Discoplax rotunda is a land crab inhabiting islands in the Indo-West Pacific oceans, from Aldabra and Mauritius to the Ryukyu Islands, Hawaii, and French Polynesia. The specie commonly lives in the supralittoral or in inland habitats.