Reproductive strategies of two invasive sun corals (Tubastraeaspp.) in the southwestern Atlantic

Abstract

The azooxanthellate sun coralsTubastraea coccineaandT. tagusensisare invasive species which were introduced into Brazilian shallow-water tropical rocky reefs by oil and gas platforms. Both species are simultaneous hermaphrodites and brooders. Histological analysis shows a continuous reproduction with the presence of different stages of development of oocytes, spermatic cysts and larvae occurring together in the same polyps (overlapping). Gametogenesis, embryogenesis, planulation and settlement were observed. Although most of the colonies showed only oocytes, none had only testes. Spermatic cysts were observed in 8.3% ofT. coccineacolonies and in 5.5% of colonies ofT. tagusensis. The maximum diameter of oocyte ofT. tagusensis(1252.5 µm) was greater thanT. coccinea(901.8 µm) and mature spermaries 700 µm in diameter formed the typical arrangement of ‘bouquets’. Although all colonies showed oocytes throughout the year, two reproductive peaks of 3–4 months duration were observed. The larvae ofT. coccineaandT. tagusensishad a competency period of 18 d in aquaria and settled near the parental colony. The investigation of gametogenesis, temporal patterns of reproduction, fecundity and sexual maturation helps to explain the rapid expansion in to new habitats and high population growth in these invasive sun corals.