Parasite communities and diet of Coris Batuensis (Pisces Labridae) from Lizard Island, Great Barrier Reef

Parasite infracommunities of the wrasse Coris batuensis (Bleeker, 1857) were analysed, and the relationship between endoparasites, diet, and host body weight inferred. Thirty-two fish were collected from Lizard Island, Australia. Percentage frequency of occurrence of prey categories in the gut was determined and abundance, prevalence and species richness of parasites were calculated. Fish mainly ate snails, bivalves and crustaceans and this did not vary with body weight. Thirty-one fish were parasitised with at least one of 21 taxa of parasites (4 ectoparasite and 17 endoparasite species), with an average of 4 species and 47 individuals per host. Tetraphyllidean cestode larvae were the most common and abundant group. Parasite life cycles are not known in detail, but small crustaceans, such as copepods and amphipods, are likely to be intermediate hosts for the cestodes, nematodes and digeneans found in C. batuensis. Molluscs, although frequent in the diet, may not be transmitting any parasite species. Numbers of prey and parasite species richness were not correlated. Composition, abundance and species richness of the parasite fauna were similar in hosts with different body weight, corresponding with C. batuensis having a similar diet throughout life. © Queensland Museum.

Dietary selectivity for the toxic cyanobacterium Lyngbya majuscula and resultant growth rates in two species of opisthobranch mollusc

Trophodynamics of blooms of the toxic marine cyanobacterium Lyngkya majuscula were investigated to determine dietary specificity in two putative grazers: the opisthobranch molluscs, Stylocheilus striatus and Bursatella leachii. S. striatus is associated with L. majuscula blooms and is known to sequester L. majuscula metabolites. The dietary specificity and toxicodynamics of B. leachii in relation to L. majuscula is less well documented. In this study we found diet history had no significant effect upon dietary selectivity of S. striatus when offered a range of plant species. However, L. majuscula chemotype may alter S. striatus' selectivity for this cyanobacterium. Daily biomass increases between small and large size groups of both species were recorded in no-choice consumption trials using L. majuscula. Both S. striatus and B. leachii preferentially consumed L. majuscula containing lyngbyatoxin-a. Increase in mass over a 10-day period in B. leachii (915%) was significantly greater than S. striatus (150%), yet S. striatus consumed greater quantities of L. majuscula (g day(-1)) and thus had a lower conversion efficiency (0.038) than B. leachii (0.081) based on sea hare weight per gram of L. majuscula consumed day(-1). Our findings suggest that growth rates and conversion efficiencies may be influenced by sea hare maximum growth potential, acquisition of secondary metabolites or diet type. (C) 2005 Elsevier B.V. All rights reserved.