BULLETIN OF MARINE SCIENCE, 81(3): 469–479, 2007 469 Bulletin of Marine Science © 2007 Rosenstiel School of Marine and Atmospheric Science of the University of Miami MODIFICATIONS OF CORALLUM MORPHOLOGY IN BLACK CORALS AS AN EFFECT OF ASSOCIATED FAUNA T. Molodtsova and N. Budaeva ABSTRACT Antipatharians, or black corals, are colonial anthozoans characterized by a chi- tinous skeletal axis covered to a varying degree with small spines. Important taxo- nomic features in this group are the size and the structure of polyps, as well as the skeleton morphology, including the mode of branching and/or pinnulation and the spine morphology. Black corals are a characteristic component of seamount suspension-feeding fauna and they often host abundant associated fauna. We ex- amined ~300 antipatharians with symbiotic polychaetes from oceanic rises of the Indo-Paciic region, representing the two families Myriopathidae and Antipathi- dae. All examined specimens had symbiotic polychaetes of the families Polynoidae [Benhamipolynoe antipathicola (Benham, 1927)] and Eunicidae (Eunice marianae Hartmann-Schröeder, 1998 and Eunice kristiani Hartmann-Schröeder, 1998). It ap- peared that the morphology of corallum and to some degree the morphology of the skeletal spines was inluenced by symbiotic polychaetes. As these features are of a high taxonomic value in antipatharians, they should be used with a caution in black corals with associated polychaete fauna. Antipatharians, or black corals, are colonial hexacorallians with a chitinous skel- eton covered with numerous tiny spines, which gave another name to this taxon: “spiny corals”. Some features of the soft tissue, such as the number of mesenteries and the size of polyps, are used as taxonomic characters in antipatharians. However, the main characters used to distinguish species of antipatharians are the morphol- ogy and arrangement of spines as well as branching and pinnulation of the corallum. Antipatharians are known to host abundant associated fauna. Among symbionts of antipatharians are more than 40 species of crustaceans, 11 species of polychaetes, mollusks, ophiuroids and others (Totton, 1923; Humes and Stock, 1973; Zevina, 1982; Humes, 1990; Pettibone, 1991; Glasby, 1994; Hartmann-Schröder and Zibrow- ius, 1998; Young, 1998; Kaizer and Hertz, 2001; Vega et al., 2002; Castro et al., 2004). Despite a growing interest in the modern literature in interrelations in ecosystems and host-symbiont and host-parasite relationships, little is known about the efect of symbiotic organisms on a hard skeleton and growth forms of colonial cnidarians. In the course of numerous cruises organized by Muséum national d’Histoire na- turelle (MNHN) in Paris and Institut de recherche pour le développement (IRD) in Nouméa in the Indo-West Paciic region, an extensive collection of black corals was obtained (Molodtsova, 2005). his collection includes numerous specimens of two groups of bottlebrush-like antipatharians associated with polychaetes of the two families Polynoidae and Eunicidae. he present study is an attempt to review inlu- ences of symbiotic polychaetes on the host antipatharians and to discuss the reliabil- ity of key taxonomic characters afected by symbiotic polychaetes. he description of antipatharian species found in the material will be published separately.