Potential spawn induction and suppression agents in Caribbean Acropora cervicornis corals of the Florida Keys

The enhanced ability to direct sexual reproduction may lead to improved restoration outcomes for Acropora cervicornis. Gravid fragments of A. cervicornis were maintained in a laboratory for two sequential trials in the seven days prior to natural spawning in the Florida Keys. Ten replicates of five chemicals known to affect spawning in various invertebrate taxa were tested. Hydrogen peroxide at 2 mM (70%) and L-5-hydroxytryptophan (5-HTP) at 5 (40%) and 20 µM (30%) induced spawning within 15.4 h, 38.8 h and 26.9 h of dosing at or above the rate of release of the control (30%) within 14.6 h. Serotonin acetate monohydrate at 1 µM (20%) and 10 µM (20%), naloxone hydrochloride dihydrate at 0.01 µM (10%) and potassium phosphate monobasic at 0.25 µM (0%) induced spawning at rates less than the control. Although the greatest number of fragments spawned using hydrogen peroxide, it was with 100% mortality. There was a significantly higher induction rate closer to natural spawn (Trial 2) compared with Trial 1 and no genotype effect. Mechanisms of action causing gamete release were not elucidated. In Caribbean staghorn corals, 5-HTP shows promise as a spawning induction agent if administered within 72 h of natural spawn and it will not result in excessive mortality. Phosphate chemicals may inhibit spawning. This is the first study of its kind on Caribbean acroporid corals and may offer an important conservation tool for biologists currently charged with restoring the imperiled Acropora reefs of the Florida Keys.