ABSTRACT: Parasitic gnathiid isopod larvae on coral reef teleosts and elasmobranchs were quantified at Lizard and Heron Islands (Great Barrier Reef), and Moreton Bay, Australia. The relationship between gnathiid abundance and host size was examined across and within species. Of the 56 species examined, 70% had gnathiids, with counts ranging from 1 to 200 per fish and the elasmobranchs having the highest numbers. Pomacentrids rarely had gnathiids. In contrast, most labrids had gnathiids. Gnathiid abundance was positively correlated with host size in the species Chlorurus sordidus, Ctenochaetus striatus, Hemigymnus melapterus, Siganus doliatus, and Thalassoma lunare, but not for Scolopsis bilineatus. Mean gnathiid abundance per host species also correlated with host size across species, even after controlling for the potential confounding effects of uneven sampling effort and host phylogeny. Thus host size explains much of the intraspecific and interspecific variation in gnathiid abundance on fish.

KEY WORDS: Gnathiidae · Ectoparasites · Coral reef fish · Host-parasite interactions · Fish size · Great Barrier Reef

Published in MEPS Vol. 164 (1998) on April 9
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998