ABSTRACT: A diverse assemblage of 16 species of hermit crabs occurs on the shores of the Quirimba Archipelago, northern Mozambique. Each species illustrated marked zonation such that they formed a distinct sequence from the subtidal across the wide intertidal zone to the supra-littoral. In addition to shore height zonation, there was distinct variation in type and range of habitat preferences. Of the 5 study islands, Quirimba and Quisiva had the greatest intertidal habitat variety and the largest number of resident hermit crab species. The number of hermit crab species peaked at 10 in the lower-shore zone and decreased upshore to 3 supra-littoral species and downshore to 8 subtidal species. In contrast, the density of hermit crab individuals peaked in the upper mid-shore, at 3 m^-2. The mid-shore zone was also the primary region of cluster formation, principally involving Clibanarius laevimanus and Clibanarius virescens, although 3 other species were also involved. The activity of the 2 semi-terrestrial species, Coenobita rugosus and Coenobita cavipes, on Quirimba Island was principally related to the light:dark cycle but was strikingly different between open and mangrove habitats. Some degree of activity took place in both species throughout a 24 h period in the mangrove habitat, where the peak of feeding activity was twice that of the open sand-scrub habitat. Wind strength was a major influence on the activity of C. rugosus and C. cavipes, reducing the number of active individuals to zero at higher wind speeds, even in thinly mangroved habitats.

KEY WORDS: Hermit crab · Intertidal · Diversity · Activity · Mangrove · Africa

Published in MEPS Vol. 154 (1997) on July 31
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997