Embriogenesis, desarrollo larval y sobrevivencia post-asentamiento del coral Orbicella annularis (Scleractinia: Merulinidae)

Introduction: Populations of the coral Orbicella annularis have shown low recruitment in the Caribbean. One of the demographic bottlenecks is the high mortality in the early stages of development. Detailed knowledge of the cycle and survival rates of these phases will allow us to assist in population recovery and reef restoration. Objective: To describe the embryogenesis and larval stages obtained by assisted fertilization and measure the settlement and survival rates of larvae on artificial substrates, before being outplanted to the reef. Methods: Six days after the full moon in September 2021, gamete bundles were collected from eight O. annu-laris colonies in Los Corales del Rosario and San Bernardo National Natural Park, Colombia and brought to the laboratory. Cross fertilization was carried out and embryonic and larval development were followed until larval settlement and survival was recorded until day 41. The larvae were kept in three tanks with filtered sea water with 126 tagged substrates, previously conditioned with crustose coralline algae. The substrates were then outplanted to the reef. Results: The onset of embryonic development occurred 1.11 hAF (hours after fertilization), when cells showed signs of the first cleavage, and lasted until 104.59 hAF when they began to metamorphose. Larvae settlement was observed on the sixth day AF. Twenty-one days after fertilization, zooxanthellae were found. Post-settlement larval survival was 27.5 %. Conclusions: In this first sexual propagation effort using O. annularis in Colombia, 1.4 % of competent larvae completed the entire development process. Although low survival rate, these results add to coral restoration efforts in the Caribbean in which species are assisted to increase the survival of corals in their early stages of development.