Reproductive biology of the hairy crab Pilumnus vespertilio (Brachyura: Pilumnidae) in the East African region

Abstract

Reproductive patterns such as gonad maturation, production and release of gametes, fecundity and moulting play a major role in the continuity of populations and their adaptations to the environment they inhabit. The present study assesses the breeding cycle, moult activity and egg production in the hairy crab Pilumnus vespertilio, a typical inhabitant of intertidal pebble and rocky substrates of East African coasts. A total of 930 crabs was collected between January and December 2002 at Inhaca Island, southern Mozambique. Both oogenesis and spermatogenesis exhibit a continuous and synchronized pattern. Maturation of the female and male gonads occurs from early winter to mid summer and spawning is in summer. Moulting females showed two major peaks (January–March and October–December) whereas a single peak was recorded in males (October–December). Pilumnus vespertilio breeds continuously with high incidence in March and December and a strong decrease from April to July. Results revealed that both temperature and rainfall were positively associated with the relative abundance of egg-bearing females. The number of eggs carried by ovigerous females increased with size, ranging from 300 to 8000. The high reproductive activity of P. vespertilio may enhance larval survival and development, which guarantees juvenile recruitment in the study area.