Reproductive periodicity, spawning and development of the deep-sea scleractinian coral Flabellum angulare
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Increasing threats to deep-sea corals highlight the need to expand knowledge of these taxa so that conservation measures can be developed. The present study focused on the reproductive patterns of the deep-sea solitary coral Flabellum angulare. A series of samples (n = 398) collected in 2006–2008 in the northwest Atlantic at depths of 925–1,430 m revealed that gametogenesis was synchronous among males and females and fluctuated seasonally. Initiation of gamete synthesis was estimated to be in August–September and spawning in June. Further analysis and daily monitoring of 30–60 individuals maintained in a flow-through mesocosm showed that gamete release occurred in March–June with a peak in May. Release of oocytes coincided with rising seawater temperatures and high deposition rates indicative of elevated water column productivity. Oocytes (900–1,200 μm diameter) were released through the oral cavity, generally in bundles of 3–5 surrounded by mesenterial filaments and attached to a thread (30–50 mm long). As oocytes became free in the water column, ovulation occurred followed by fertilization. Eggs/embryos initially remained on the tentacles of the spawner before either falling onto the substratum or floating to the surface. The embryos developed into planula larvae measuring 2–3 mm in length within about 24 h. Together, these findings shed new light on the strategies used by deep-sea corals to maximize their reproductive success.
KeywordsScleractinian Coral Mature Oocyte Vitellogenic Oocyte Gamete Release Solitary Coral
We gratefully acknowledge the financial support and assistance of the Department of Fisheries and Oceans Canada (DFO) aboard the CCGS Teleost and Hudson as well as the technical skills of the ROPOS team. Special thanks to V. Wareham for her help during the collection and cataloguing of specimens, G. Doyle for long hours of sample processing and J. Foote for assisting with histology. Additional funding was obtained from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI).
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