Reproductive biology of the Antarctic sea pen Malacobelemnon daytoni (Octocorallia, Pennatulacea, Kophobelemnidae).

NATALIA SERVETTO; LUCIANA TORRE; RICARDO SAHADE

Polar Research

Norwegian Polar Institute

Año: 2013 vol. 32

1751-8369

The reproductive biology of the sea pen Malacobelemnon daytoni was studied atPotter Cove, South Shetland Islands, where it is one of the dominant species inshallow waters. Specimens collected at 1522 m depth were examined byhistological analysis. M. daytoni is gonochoristic and exhibited a sex ratio of 1:1.Oocyte sizes (300 mm) and the absence of embryos or newly developedlarvae in the colonies suggest that this species can have lecithotrophic larvaeand experience external fertilization. This life strategy is in line with othermembers of the group and supports the hypothesis that this could be aphylogenetically fixed trait for pennatulids. It was observed that oocytes weregenerated by gastrodermic tissue and released to the longitudinal canal.Thereafter, they migrate along the canal until they reach maturity and arereleased by autozooids at the top of the colonies. This striking feature has notyet been reported for other pennatulaceans. Mature oocytes were observedfrom colonies of 15 mm in length, suggesting that sexual maturity can bereached rapidly. This is contrary to what is hypothesized for the vast majorityof Antarctic benthic invertebrates, namely that rates of activities associatedwith development, reproduction and growth are almost universally very slow.This strategy may also explain the ecological success of M. daytoni in areas withhigh ice impact as in the shallow waters of Potter Cove.