Reproductive biology of the deep-sea pennatulacean Anthoptilum murrayi (Cnidaria, Octocorallia)

Abstract

Anthoptilum murrayi has been reported from the North Atlantic, northern Mid-Atlantic Ridge, Indian Ocean and in waters around New Zealand and Australia. Recently, this species was also recorded in deep waters off Brazil, southwestern Atlantic. It was from this region (13° to 22° S) that specimens were collected, in 1300 to 1799 m, to determine the reproductive biology of A. murrayi using histological methods. The colony polyparium was divided into 3 zones (distal, medial and basal) to evaluate differences in gamete development between zones; dissected polyps were examined from the 3 zones to estimate fecundity. The species appears to display a continuous and long breeding activity rather than any seasonal reproductive pattern. Most oocytes were in the earliest stages of development and basal polyps presented the highest frequency of small eggs. The large mature oocytes (up to 1200 μm) indicate that A. murrayi produces lecithotrophic larvae. Females had 0 to 90 oocytes per polyp and 25 713 to 35 918 oocytes per colony. Male colonies of similar size to the female samples were shown to have 6 to 76 cysts per polyp and 14 014 to 27 019 cysts per colony. A. murrayi is a sessile gonochoric species with a 1:1 sex ratio and is most likely a broadcast spawner. The species has high fecundity, large eggs that could represent larger targets for sperm, primitive spermatophores, as well as a large number of polyps per colony. These factors, along with a patchy distribution, would enhance the chance of fertilization for A. murrayi and may guarantee a successful reproductive strategy for this species.