Reproductive biology of the deep-water coral Acanella arbuscula (Phylum Cnidaria: Class Anthozoa: Order Alcyonacea), northwest Atlantic

Knowledge of the reproductive life-history of deep-water corals is important for assessing their vulnerability to anthropogenic impacts. Yet, the reproductive biology of many deep-water corals, especially members of the subclass Octocorallia, has not been examined. We used histological techniques to describe the reproductive biology of the deep-water gorgonian coral Acanella arbuscula from the northwest Atlantic. All colonies examined were gonochoric, and no embryos or planula larvae were observed in the polyps. Mean polyp-level fecundity (females: 21.0±17.5 oocytes polyp−1, and males: 13.9±13.5 sperm sacs polyp−1) is high compared to other deep-water gorgonians, and polyps closer to the branch tips had the highest fecundities in both females and males. The presence of large oocytes (maximum diameter 717.8 μm) suggests that A. arbuscula produces lecithotrophic larvae. Despite the potentially high fecundity and small size at first reproduction, the paucity of information on dispersal and recruitment, combined with its longevity, vulnerability to bottom fishing gear, and ecological role as a structure-forming species, still warrants the classification of A. arbuscula as a vulnerable marine ecosystem indicator.

► We examine the reproductive biology of the deep-water gorgonian Acanella arbuscula.
► The number of gametes polyp−1 is high in A. arbuscula compared to other deep-water gorgonians.
► Colonies of A. arbuscula are gonochoric, and no planula larvae were observed.
► As in other octocorals, A. arbuscula shows a high degree of intra-colony variation in polyp-level fecundity.