Species Descriptions and Ecological Observations of Black Corals (antip a Tharia) from Trinidad

Eight species of. black coral were found off northwest Trinidad, West Indies. Antipathes thamnea n. sp. is described and compared with specimens of the closely related species A. hirta Gray, 1857 and A. barbadensis (Brook), 1889. Two other species, A. atlantica Gray, 1857 and A. gracilis Gray, 1860, are-redescribed and compared. A sheltered site and one exposed to strong currents were sampled; A. gracilis was commoner at the former site and A. thamnea at the latter. Most species formed fan-shaped colonies orientated normal to the mainly unidirectional currents~ Fans were usually dishshaped with polyps borne on the convex downcurrent side~ Colonies of A. atlantica from the exposed site were found to be more densely branched and to have thicker stems than sheltered colonies. Stems from both sites were elliptical in cross section with the long axis of the ellipse at right angles to the fan. Stomachs of polyps of four species were found to contain copepod remains. The occurrence of epizoites was noted; stalked barnacles were common. The results are discussed with relation to the nutritional and mechanical aspects of suspension feeding in currents. . Between north-west Trinidad and Venezuela lies a chain of islands separated by deep (200-300 m) channels of "bocas." These channels comprise the Dragon's Mouth through which a part of the Guyana Current flows north into the Caribbean Sea (Gade, 1961). The current can be swift, particularly when aided by a falling tide, and creates turbulence in the bocas bringing relatively cool water (about 20°C) up close to the surface. The water contains considerable quantities of seston, and light attenuates with depth more rapidly than is normal in the Caribbean. The result is that, within aqualung diving depth, a cool dark environment exists in which a number of relatively deep-water organisms occur. These include ahermatypic corals, deep-water gorgonians, euryalous brittle-stars and black corals. Difficulty was experienced in the identification of three species of black coral which had pinnate branches resembling bottle-brushes. One of these is new to science and is described here under the name ofAntipathes thamnea new species. The other two ar~ referred to A. hirta Gray, 1857 and A. barbadensis (Brook), 1889 and these species are redescribed on the basis of the new material. Difficulty was also experienced in distinguishing two fan-shaped species, A. atlanlica Gray, 1857 and A. gracilis Gray, 1860. These two species are contrasted and redescribed. Little is known of the way of life of black corals (Grigg, 1965; Opresko, 1972) and this area provided a rare opportunity for the direct observation of colonies in the field. Observations were made on distribution,. orientation, morphology of colonies under different conditions of water movement, feeding and epizoites.