Environmental control of gonadal development in the tropical damselfish Chrysiptera cyanea

Abstract

Photoperiod and temperature are potent environmental factors regulating the reproductive cycle of temperate fish. It is unclear whether fish in the tropics utilize these environmental factors for initiation and termination of their reproductive activity. The aim of this study was to examine the involvement of photoperiod and temperature in ovarian development of sapphire devil, Chrysiptera cyanea, which is a reef-associated tropical damselfish. Monthly collections of individuals in the experimental region (26°42′N, 127°52′E) revealed an increase in the gonadosomatic index (GSI) and appearance of vitellogenic oocytes in ovaries from March to August. Post-ovulated follicles and yolk-laden oocytes coexisted in some ovaries from May to August. These results suggest that the sapphire devil in this region has a restricted reproductive season with repeated spawnings. Rearing the fish during the resting phase (December) under experimental conditions of a long photoperiod (LD 14:10) at 31°C for 15 days and at 25 or 31°C for 60 days resulted in a significant increase in GSI and induction of vitellogenic oocytes, whereas a short photoperiod (LD 10:14) at the same temperatures failed to induce oocytes at the yolk stages. Long-term rearing of the fish at 31°C caused regression of vitellogenic oocytes. During the reproductive season, the fish reared at 25°C had higher spawning frequency than those at 20 and 30°C. It is concluded that photoperiod and temperature are involved in the regulation of gonadal development and a long photoperiod within a suitable range of water temperatures is required for continuity of reproductive activities.

Keywords:

• Histology
• ovary
• photoperiod
• Pomacentridae
• reproductive cycle
• temperature

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

All experiments were performed in compliance with the animal care and use committee guidelines of the University of the Ryukyus, and with the regulations for the care and use of laboratory animals in Japan. This study was supported in part by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS) to AT and by the 21st Century COE program of the University of the Ryukyus ‘The Comprehensive Analyses on Biodiversity in Coral Reef and Island Ecosystems in Asian and Pacific Regions’ from the Ministry of Education, Culture, Sports, Science and Technology, Japan. This is a contribution of Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Additional information

Notes on contributors

Pouvave Fainuulelei

Present address: Department of Fisheries and Agriculture, Government of Samoa, Apia, Samoa