Histological description of new specialized reproductive structures in Atlantic Tubastraea corals (Scleractinia, Dendrophylliidae)

Abstract

Abstract The family Dendrophylliidae comprises a genus of azooxanthellate corals, Tubastraea (also known as ‘sun corals’ or ‘cup corals’), native from the Indo-Pacific and introduced into the Atlantic Ocean in the early 1940s. In Brazil, Tubastraea colonies were first registered on oil platforms on the northern coast of Rio de Janeiro state (22°S) in the late 1980s. Two decades later, these corals were for the first time identified in the Todos-os-Santos Bay (Bahia state, 13°S), a warmer environment with diverse marine ecosystems including estuaries, mangroves, and coral reefs. Intending to describe the biological cycle of exotic dendrophylliids from the Brazilian northeastern coast, histological analyses revealed three new reproductive structures for Scleractinia: (1) a mucin layer composed of acid glycoproteins surrounding immature sun coral oocytes, (2) trophonema or specialized cells connecting the oocyte to the adjacent gastrodermis, and (3) nucleolini, small condensations in nucleoli.