DETECTION OF ESTRADIOL-17-BETA DURING A MASS CORAL SPAWN

The steroid estradiol-17-beta (E2) is associated with female gametogenesis in all vertebrates and many invertebrates. This is the first report of estrogens in scleractinian corals. Seawater and egg slicks were collected during a mass coral spawn at Ningaloo reef, Western Australia for the measurement of total phosphate (TP) and E2. Total P in the water column increased 600 times, from 0.5-mu-M to 300-mu-M. Concentrations of E2 increased nearly 8 fold during the spawn, from 55 to 420 pg/100 ml seawater. Coral eggs collected from egg slicks contained 368 +/- 40 pg E2/g dry wt of eggs. Estrogen may be a key hormone in a simple endocrine system of scleractinian corals that synchronizes growth and development of coral oocytes. Its potential role in triggering spawning via chemical messengers in the water column warrants further research.