Gametogenesis and Early Development of the Temperate Coralastrangia Danae(anthozoa: Scleractinia)

The coral Astrangia danae is dioecious, with an early age of first reproduction. 2. In Narragansett Bay, this species exhibits an annual reproductive cycle with gametogenesis starting in March-April. Spawning occurs during August, and vestigial gametes are absorbed during the winter months. 3. Gametes originate from interstitial cells which differentiate in the mesenterial mesoglea. 4. Ova are 100-130-µm in diameter and sperm are 2-3-µm in length, excluding the tails. Egg production was estimated at up to 6000 eggs per polyp. 5. Fertilization and development are external; no fertilization membrane was seen even though a layer of cortical vesicles was present before fertilization. 6. Embryonic cell divisions are around 30 min apart and the larval planual stage is reached within 12-15 hr after fertilization. Larval settlement was not observed. 7. Ova from colonies containing zooxanthellae did not contain zooxanthellae when spawned.