On Some Octocorallia (Cnidaria: Anthozoa: Alcyonacea) From Singapore, With A Description Of A New Cladiella Species

Abstract

Octocorallia (Cnidaria: Anthozoa) from Singapore were collected and identifi ed in a survey conducted in 1999. Colonies collected previously, between 1993 and 1997, were also studied. The entire collection of ~170 specimens yielded 25 species of the families Helioporidae, Alcyoniidae, Paraclcyoniidae, Xeniidae and Briareidae. Their distribution is limited to six m depth, due to high sediment levels and limited light penetration. The collection also yielded Cladiella hartogi, a new species (family Alcyonacea), which is described. All the other species are new zoogeographical records for Singapore. A comparison of species composition of octocorals collected in Singapore between 1993 and 1977 and those collected in 1999 revealed that out of the total number of species, 12 were found in both periods, whereas seven species, which had been collected during the earlier years, were no longer recorded in 1999. Notably, however, six species that are rare on Singapore reefs were recorded only in the 1999 survey and not in the earlier ones. It is not yet clear whether these differences in species composition indeed imply changes over time in the octocoral fauna, or may refl ect a sampling bias. The inclusion of octocorals in Singapore reef-monitoring programs will undoubtedly shed light on possible temporal changes in their species composition. The fi ndings do indicate, however, that the fl eshy octocoral fauna of Singapore is rather impoverished compared to other reefs in the region.