Population structure and breeding biology of the hairy crab Pilumnus vespertilio (Fabricius, 1793) (Crustacea: Brachyura: Pilumnidae) in southern Mozambique

Abstract

The population structure and reproduction of Pilumnus vespertilio were studied for the first time in Mozambique. Random samples of crabs were taken monthly from January to December 2002 from a pebble area of Inhaca Island, southern Mozambique. A clear sexual dimorphism was observed in the present population with males reaching greater sizes than females. Sex ratio was female‐biased, and the monthly size–frequency distributions were often bimodal. The annual reproductive cycle of Pilumnus vespertilio was continuous with peaks of breeding in summer. Results suggest that embryonic development may be synchronized within the population as a result of the very high reproductive activity observed in summer. Juveniles are recruited mostly in winter in the study area.

Keywords:

• Breeding biology
• Inhaca Island
• Mozambique
• Pilumnus vespertilio
• population structure
• sex ratio

Acknowledgements

I would like to thank the Marine Biological Station of Inhaca Island (EBMI) for support and especially Sergio Mapanga for tireless help. Thanks are due to the National Institute of Meteorology for providing the environmental data. Daniela Abreu, Juan Antonio Baeza and Winston D. Emmerson provided helpful suggestions on an earlier draft of the manuscript. Thanks are also extended to two anonymous referees for useful comments that improved this manuscript.

Notes

n, number of individuals.

^aSignificant difference from the expected 1:1 ratio (χ²‐test, P<0.05).