Larval development and survivorship in the corals Favia favus and Platygyra lamellina

Two Red Sea faviid species, Favia favus and Platygyra lamellina spawn eggs and sperm once a year, during the summer. External fertilization occurs 0.5 h after spawning, and mobile gastrulae appear 20 h later. Four stages in the early ontogenesis of these corals are described. The slow development (2–3 months) to the polyp stage in broadcasting species is attributed to the lack of zooxanthellae in their planulae and their appearance in the primary polyp only at a later stage. Survivorship of one-month-old primary polyps is ca 0.21% and 0.25% in F. favus and P. lamellina respectively, from the populations of 2–9-day-old planulae. Despite these low rates of survival, both species form dense populations in the Gulf of Eilat.