Ovarian structure and mode of egg production in the seaweed pipefish Syngnathus schlegeli (Syngnathidae)
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This study investigated ovarian structure and mode of egg production in the seaweed pipefish, Syngnathus schlegeli. The ovary had a rolled sheet-like structure where developing follicles were arranged serially in sequence according to their development, with a single germinal ridge running along the edge of the sheet. Oocytes of various developmental stages were concomitantly present in the ovary, and the number of mature eggs increased continuously over time, indicating that egg production is asynchronous. This would be a physiological basis for multiple spawning within a short time span associated with polygamy in this fish.
KeywordsOogenesis Spawning Syngnathus schlegeli Syngnathidae Mating system
We are grateful to S. Iwasaki for technical support in field and laboratory work. We thank K. Hidaka, H. Issiki, Y. Kamimura, H. Kinoshita, T. Morita, Y. Nakata, E. Sawai, J. Shoji, and A. Tada for their help in collecting fish. We also thank S. Watanabe for technical advice for rearing fish, J. Shibata for advice on statistical analyses, and anonymous reviewers for helpful comments. This research was supported by the Japan Society for the Promotion of Science for Young Scientists to A.S.