The plasticity of gonad development of sexual reproduction in a scleractinian coral, Porites lichen

Abstract

Metazoans have evolved a complexity of sexual system and gonad development, however, sexual reproduction of scleractinian corals is not well understood. This study aimed to address the sexual system and gametogenesis in Parkes lichen, a common species in the Indo-West Pacific. This study represents the first description of sexual system, which were determined by histological analysis of the samples collected in northern Taiwan. In addition, female and hermaphroditic colonies were separately cultured in aquarium to further monitor the release of eggs/larvae and thereby confirm the breeding system. The results demonstrate that P. lichen is a polygamodioecious brooder and displays seasonal gametogenesis and embryogenesis that ends in late summer. In hermaphroditic colonies, male polyps are predominant and hermaphroditic polyps make up a very small percent (1%-19.3%). In addition, two new gametogenic features were observed from the histological analysis: 1) oocytes developed within the spermaries in hermaphroditic polyps during the early stage of gametogenesis and 2) melanin granular cells were clustered in spermaries in both male and hermaphroditic colonies. This study demonstrated the plasticity of gametogenesis and melanin related cells appeared in corals, which provides an important information to explore hormones and molecular mechanism involving in gonadal arrangement and production of melanin for further studies.