Distribution and reproductive ecology of the Antarctic octocoral Ainigmaptilon antarcticum in the Weddell Sea

Abstract

The spatial distribution, density and reproductive ecology of Ainigmaptilon antarcticum was studied using samples (colonies) collected during the EASIZ (Ecology of the Antarctic Sea Ice Zone) cruises I, II, and III, (1996, 1998, and 2000). Samples were taken using Agassiz and bottom trawls between 150 and 600 m depth in conjunction with a Remotely Operated Vehicle (ROV, video recording transects). A. antarcticum showed a very patchy distribution with a mean density of 12 per 100 m2 (SD ± 23) in the study area. This gorgonian species is gonochoric with a sex ratio of 1:1. Two size classes of oocytes in different developmental stages were observed in summer (January to March) and autumn (April to May), ranging from 25 to 700 µm in summer, and from 20 to 900 µm in autumn. Differences in developmental stages among different zones of the colony were observed. The apical and medial part showed the highest fecundity. The distribution of gonad size differed between summer and autumn. The relative frequency of the largest oocyte size class decreased in the autumn samples. No larvae were found. The results are discussed in the context of the relationship between reproductive strategies of marine invertebrates and environmental factors.