Reproductive morphology of three species of deep-water precious corals from the Hawaiian Archipelago : Gerardia Sp., Corallium secundum, and Corallium lauuense

Abstract

Three species of deep-sea corals were collected from several locations in the Hawaiian Archipelago. These species have been called "precious corals" because of their extensive use in the jewelry industry. Two octocorals Corallium lauuense Bayer, 1956 (red coral) and Corallium secundum Dana, 1846 (pink coral), and a zoanthid, Gerardia sp. (gold coral) collected between August and November in 1998-2004, were all histologically analysed for reproductive tissues. All three species of precious corals appear to be gonochoric (both males and females of all species being identified—though with C. lauuense more reproductive polyps are needed to conclusively confirm this), with the two species of Corallium having reproductive material contained within siphonozooids rather than the main polyp (autozoid). Maximum oocyte sizes were: Gerardia sp. ∼300 μm, C. secundum ∼600 μm, and C. lauuense ∼660 μm. All three species are hypothesized to have spawned during the collection season. Gerardia was observed spawning during collection, and histological sections of the two Corallium species show areas where gametes appear to be missing. Gerardia sp. has a single cohort of gametes developing, which may suggest seasonal reproduction, and the two Corallium species show multiple sizes present in single individuals, suggesting a periodic or quasi-continuous reproductive periodicity.