JournalofFish Diseass 1985, 8, 129-134 SHORT COMMUNICATION Lesions of a rock beauty, Holacanthus tricolor (Bloch), from Puerto Rico J. M. GRIZZLE Department of Fisheries and Allied Aquacultures, Auburn University, Alabama, U.S.A. E. H. WILLIAMS JR Department of Marine Sciences, University of Puerto Rico, Mayaguez, Puerto Rico Abnormal cutaneous melanin pigmentation was noted in rock beauties, Holacanthus tricolor (Bloch), collected off south-western Puerto Rico (Colin 1982). An 18-cm standard length rock beauty collected at a depth of 18-3 m at the Department of Marine Sciences buoy on the insular shelf edge off La Parguera, Puerto Rico in May 1978 had three black nodules on the external body surfaee, as well as areas of abnormally dark skin without nodule formation over the lateral head and the dorsal and ventral caudal peduncle (Fig. 1; see normal pigmentation of the rock beauty in Bohlke & Chaplin [1968], p. 17). This fish was photographed freshly dead in the laboratory, and preserved in 10% formalin. One of the black nodules was located on the lips and the other two were on the body, one adjacent to the insertion of the right pelvic fin and the other immediately anterior to the anal fin (Figs 1 & 2). The labial mass was oval, 50 mm long and was elevated 10 mm above the surrounding skin. The truncal nodules were round, 43-45 mm in diameter and 8-10 mm high. All three nodules were firm and had roughened surfaces. Sections of lesions were made from paraffin-wax-embedded material and stained with haematoxylin and eosin (H&E) or periodic acid-Schiff s stains. Microscope slides of the lesions were deposited in the Registry of Tumors of Lower Animals, Smithsonian Institution, Washington, D.C, U.S.A (RTLA 2554) (Harshbarger 1982). The melanistic areas of the caudal peduncle of this specimen were dark because of accumulation of large numbers of melanophores in the deep epidermis and superficial dermis. The epidermis was intact over the caudal peduncle. Associated with the hyperpigmentation of the caudal peduncle of this fish were encysted turbellarian parasites in the connective tissue between fin rays (Fig. 3). Spherical, encapsulated masses of acellular debris, probably the result of earlier helminth infections of the fins, were also present (Fig. 4). Areas of increased melanin production in fishes are frequently associated with encysted parasites (Roberts 1975). The melanism reported in rock beauties by Colin (1982) may have been caused by encysted turbellarians. Histologically, the labial mass consisted of highly vascularized connective tissue with numerous blunt to knobby papillae radiating peripherally. The epidermis was eroded, and a layer of melanophores outlined the edges of the papillae (Figs 5 c& 6). Melanophores Correspondence: Dr J. M. Grizzle, Dcparinicnt of Fisheries and Allied Aquacultures, Auburn University Alabama 36849, U.S.A. ^' 9 129