The occurrence, distribution and pathology associated with gnathiid isopodlarvae infecting the epaulette shark, Hemiscyllium ocellatum

Gnathiid isopod praniza larvae were found to infect the epaulette shark Hem iscyllium ocellatum. All sharks carried larvae on their external body surfa ce, with the preferred attachment site in both sexes around the cloaca (P<0 .05). The claspers were the second site of preference in male sharks. Withi n the buccal and branchial cavities, about 16% of larvae were attached to t he roof and floor of the mouth and 84% attached to the gills. A significant positive correlation existed between larval number and fish size. Histolog ical examination showed that larval attachment in the buccal cavity elicite d variable responses, the most severe being a loss of epithelium and compre ssion of underlying tissue. No host cellular response or tissue proliferati on was observed. Praniza attached preferentially to the efferent side of gi ll filaments (relative to blood flow), and caused loss of epithelium, compr ession of tissue, and a small amount of connective tissue proliferation. At tachment to the gill septum or to the afferent side of the gill filament ca used lamellar disruption, a cellular inflammatory response, and connective tissue proliferation. Scanning electron microscopy showed little obvious pr aniza-induced gill damage, other than localised tissue distortion to form " pockets" around larvae attached between filaments. The results suggest that praniza larvae do not cause sufficient tissue damage to adversely affect t he health of this shark species. (C) 1999 Australian Society for Parasitolo gy. Published by Elsevier Science Ltd. All rights reserved.