Parasites and cleaning behaviour in damselfishes

Abstract

Pomacentrids (damselfishes) are one of the most common and diverse group of marine fishes found on coral reefs. However, their digenean fauna and cleaning interactions with the bluestreak cleaner wrasse, Labroides dimidiatus, are poorly studied. This thesis explores the digenean trematode fauna in damselfishes from Lizard Island, Great Barrier Reef (GBR), Australia and examines several aspects of the role of L. dimidiatus in the recruitment of young damselfishes.My first study aimed to expand our current knowledge of the digenean trematode fauna of damselfishes by examining this group of fishes from Lizard Island on the northern GBR. In a comprehensive study of the digenean trematodes of damselfishes, 358 individuals from 32 species of damselfishes were examined. I found 19 species of digeneans, 54 host/parasite combinations, 18were new host records, and three were new species (Fellodistomidae n. sp., Gyliauchenidae n. sp.and Pseudobacciger cheneyae). Combined molecular and morphological analyses show that Hysterolecitha nahaensis, the single most common trematode, comprises a complex of cryptic species rather than just one species. This work highlights the importance of using both techniques in conjunction in order to identify digenean species. The host-specificity of digeneans within this group of fishes is relatively low. Most of the species possess either euryxenic (infecting multiple related species) or stenoxenic (infecting a diverse range of hosts) specificity, with only a handful of species being convincingly oioxenic (only found in one host species). Overall, the trematode richness in pomacentrid fishes is relatively low compared with that of many other coral reef fish families. The richness is probably best explained by the small size of most pomacentrids. In terms of beta diversity, of the total 23 trematode species having now been reported for the GBR in pomacentrids, just 14 are shared between Heron and Lizard Island. Five species have been recorded only from Lizard Island and four only from Heron Island. A total of 14 species reported from the two sites can be classified as core pomacentrid-specific parasites.I then examined whether the abundance and diversity of damselfish recruits differed on reefs relative to reefs from which cleaner wrasse had been removed for 12 years. Past studies have shown that cleaner wrasse enhance abundance and diversity of adult resident damselfishes (species that are site-attached), however, it is not known whether this effect occurs at recruitment or is driven by post-settlement events such as migration or differential mortality. I characterised the abundance of damselfish recruits on reefs with and without cleaner wrasse for five days in each of three lunar cycles, beginning four days after the new moon (November, December and January). The total abundance of damselfish recruits and specifically two species, Chrysiptera rollandi and P. amboinensis, was higher on reefs with cleaner wrasse than on reefs without. However, overall iii species diversity of damself...