Ex situspawning, larval development, and settlement in the massive reef-building coralPorites lobatain Palau

Abstract

AbstractReproduction, embryological development, and settlement of corals are critical for survival of coral reefs through larval propagation. Yet, for many species of corals, a basic understanding of the early life-history stages is lacking. In this study, we report our observations forex situreproduction in the massive reef-building coralPorites lobataacross two years. Spawning occurred in April and May, on the first day after the full moon with at least two hours of darkness between sunset and moonrise, on a rising tide. Only a small proportion of corals observed had mature gametes or spawned (17 – 35%). Eggs were 185 – 311 μm in diameter, spherical, homogenous, and provisioned with 95 – 155 Symbiodiniaceae algae. Males spawned before females, andex situfertilization rates were high for the first 2 hours after egg release.P. lobatalarvae were elliptical, approximately 300 μm long, and symbiotic. Just two days after fertilization, many larvae swam near the bottom of culture dishes and were competent to settle. Settlers began calcification two days after metamorphosis, and tentacles were developed 10 days after attachment. Our observations contrast with previous studies by suggesting an abbreviated pelagic larval period inP. lobata, which could lead to the isolation of some populations. The high thermal tolerance and a broad geographic range ofP. lobatasuggest this species could locally adapt to a wide range of environmental conditions, especially if larvae are locally retained. The results of this study can inform future work on reproduction, larval biology, dispersal, and recruitment ofP. lobata, which could have an ecological advantage over less resilient coral species under future climate change.