The reproductive biology of Parazoanthus parasiticus (Hexacorallia: Zoanthidea) in Bermuda

The zooxanthellate macrocnemic zoanthid Parazoanthus parasiticus lives at densities of 3–10 cm^–2 in the chimney sponge Callyspongia vaginalis in Bermuda. It is gonochoric and oviparous. Small oocytes appear in the mesenteries in February–March, grow slowly at first, then increase volume rapidly as seawater temperature passes 27 °C in July. In 1993, oocytes were found to have been shed over 2–3 days around the full moon on 1 September, with inferred small spawnings over the preceding and following full moons. Reproduction had finished by November. In 1999, spawning of azooxanthellate eggs ~250 μm diameter took place on 28 August, two nights after full moon. Spawnings therefore precede those known for four oviparous scleractinians and one gorgonian in Bermudian waters by about a week. The eggs are not shed in bundles and lack zooxanthellae. The unknown embryonic development and larval type in macrocnemic zoanthids is discussed and remains to be resolved by further study with P. parasiticus.

Key words: Macrocnemina, zoanthina, gonochorism, spawning, Castle Harbour, zooxanthellae