Sexual reproduction in the Mediterranean endemic orange coral Astroides calycularis (Scleractinia, Dendrophylliidae).

Astroides calycularis (Pallas, 1766) is a common endemic azooxanthellate scleractinian coral living in the southwestern Mediterranean Sea, generally in shaded habitats, below overhangs, or at cave entrances, from the surface to 50 m depth. The annual reproductive cycle of A. calycularis (gamete development in relation to environmental parameters, planulation timing, size at sexual maturity, fecundity, and sex ratio) was studied at Palinuro in the southern Tyrrhenian Sea (Italy) from April 2004 to September 2005. Colonies were gonochoric, were mature at 3–4 cm2 in area, and had a sex ratio of 1:1. Polyps were sexually mature at 3–4 mm length (maximum diameter of the oral disc), and the females brooded their larvae. The maturation of spermaries took 7 mo and that of oocytes took over 12 mo. The rate of gamete development increased significantly from November to March. Fertilization occurred from April to May, with planulation in June. Mature oocytes ranged from 400 to 1590 μm and planulae size was 1850 μm (oral–aboral axis). Seasonal variation in seawater temperature and photoperiod likely play an important role in regulating reproductive events. The amount of energy devoted to male gametogenesis (quantified by gamete index) was significantly higher than female gametogenesis. In relation to other dendrophylliids, A. calycularis presents an intermediate reproductive strategy on the r-K continuum.