ECOLOGICAL ASPECTS OF THE POPULATIONS OF THE CRAB DOTILLA-FENESTRATA (HILGENDORF, 1869) (BRACHYURA, OCYPODIDAE), IN THE TIDAL FLATS OF INHACA ISLAND (MOZAMBIQUE)

The population of Dotilla fenestrata of Inhaca island was studied, on the basis of fortnightly sampling during a period of four months. At t hree tidal levels and in two collecting transects, crabs were counted, sexed and measured, and eggs counted. Results indicate a preference o f the crabs for the lower level, although there is a high degree of va riability of abundance in relation to the unstable profiles of the san d banks. Diameter of burrow entrance is strongly correlated to crab si ze, which may prevent predation by larger animals. The rhythm of emerg ence was studied, comparing neap to spring tides. Results indicate tha t crabs are more rapid in initiating surface activity, mainly feeding, during neap tides, and during spring tides the delay is related to ti de level. Feeding rhythm is independent of animal size, but weight of feeding pellets produced increases with crab size. Sponging rhythm dec reases with crab size, which suggests a more efficient water intake by larger animals.