Analysis of the reproductive biology of the non-zooxanthellate colonial coral Astroides calycularis (Scleractinia, Dendrophyllidae) in CO2 vent habitats of Ischia Island.

Natural populations living near underwater volcanic CO₂ vents offer a valuable model for understanding how species may cope with future ocean acidification driven by global climate change. This study examines the reproductive biology of Astroides calycularis, a temperate non-zooxanthellate colonial scleractinian coral. The reproductive pattern of a population in a CO2 vent site, at Grotta del Mago, was compared to a control population at ambient pH along the coast of Ischia (Italy). Histological analysis and measurement of germ cells were performed to determine abundance, size, and developmental stages of oocytes and spermaries in the two compared populations.