Reproduction and growth of Anthomastus ritteri (Octocorallia: Alcyonacea) from Monterey Bay, California, USA

Anthomastus ritteri Nutting, 1909 is a deep-sea alcyonacean from the Pacific coast of California, USA, and Baja California, Mexico. Although descriptive studies exist, detailed information on the reproduction and life history of any species of Anthomastus or on deep-sea octocorals in general is sparse. Laboratory specimens of A. ritteri were studied with respect to their reproductive biology, timing of larval settlement, and growth rates. Collected A. ritteri colonies were dioecious larval brooders that exhibited continuous reproduction. Developing larvae were brooded in the siphonozooids, with large colonies capable of containing over 4000 oocytes and larvae. The demersal planula larvae were capable of settlement 2 days after release. The longest competency period recorded in the laboratory was 123 days. A Gompertz growth model was based on the size-specific growth rates of 15 colonies. Growth was slow for the first 1-2 years, but increased when colonies comprised three to four feeding polyps. Growth slowed in adult colonies, approaching an asymptotic size. In the model, A. ritteri approached asymptotic size between 25 and 30 years of age. This age is greater than those reported for tropical gorgonian colonies. These results agree with the general notion that growth rates are reduced and longevity increased in deep-sea species.