Mate guarding behaviour in the supralittoral isopod, Ligia dentipes (Oniscidea) from the Andaman and Nicobar Islands

Abstract

Precopulatory mate guarding is a characteristic feature in the mating behaviour of many Malacostraca, and a necessary prerequisite for those species in which female receptivity for males is restricted to a short period of time after the pubertal/reproductive moult. This study deals with the pre-mate guarding behaviour of the semi-terrestrial isopod Ligia dentipes living in the crevices of coral boulders and rocks in the supralittoral region of the Andaman Islands. As in other isopods, moulting in L. dentipes is biphasic, in which the posterior body part invariably moults first. The guarding male aids the female partner in the removal of the moulted exoskeleton. Mating occurs immediately after the posterior body exuviates. The male leaves the female after copulation and goes in search of another receptive female, demonstrating a polygamous mating system in these isopods. The mated females also re-mate with several other males without mate guarding. Females that had mated several times produced more young, compared to females mated only once in the laboratory. Female receptivity ceases following moulting of the anterior half. Intrasexual encounters among males lead to the large males acquiring receptive females. This study reveals interesting deviations from the general pattern of mate guarding already reported in other isopods and decapods. The evolutionary and ecological significances of mate guarding, intrasexual and intersexual conflicts, found in these semi-terrestrial isopods, are discussed.

Keywords:

• Crustacea
• sexual conflicts
• biphasic moulting
• female receptivity

Acknowledgements

The authors gratefully acknowledge the financial support given by the Earth System Sciences Organization (ESSO), Ministry of Earth Sciences, Government of India. The authors are thankful to Dr M.A. Atmanand, Director, ESSO-National Institute of Ocean Technology, Ministry of Earth Sciences, Government of India, for constant suggestions and encouragements to carry out this work. We profoundly thank Dr M. Vijayakumaran and two anonymous reviewers for their critical comments and suggestions to improve this paper. We are also thankful to Mrs Mary Leema Thilakam for statistical analysis. Dr T. Subramoniam is thankful to Indian National Science Academy, New Delhi, India for offering him honorary Scientist position at NIOT.