Female sexual receptivity in the sandy-beach isopod Tylos granuliferus (Crustacea)

Abstract

The reproductive cycle of female Tylos granuliferus was investigated in laboratory conditions. We focused our experiments on female copulative timing for effective insemination and on female sexual receptivity for reproduction. We used females who were isolated from males along with delayed copulation. The female reproductive cycle of T. granuliferus is related to the parturial moult cycle. Females copulate soon after shedding the posterior half of their body cuticle through anterior shedding with a shedding interval of 2 days. Copulation ends just before oviposition. The optimum timing for copulation is within a few days after completion of the parturial moult. Oviposition immediately follows insemination. Without copulation, females do not oviposit their eggs. Pre-copulatory mate guarding by males and sperm storage by females for future broods do not appear to occur in this species. Isolated females have a sexual receptive period of 12 days during the early stages of the reproductive cycle and cannot produce mancas if insemination is more than 10 days later after the parturial moult. We propose that females are exposed to oviposition-stimulating factors at copulation to oviposit the fertilized eggs into their marsupium.

Keywords:

• copulation
• sexual receptivity
• isopod
• female reproduction
• parturial moult cycle

Acknowledgements

We thank Dr. T. Kimura (University of Kitasato) for allowing us to use his laboratory facilities and for assisting us in completing this manuscript. We are grateful to Mrs. C. Uno and Mr. T. Suzuki for their help during our field work.