Parasites and cleaning behaviour in damselfishes Derek Sun BMarSt, Honours I A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2015 School of Biological Sciences i 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, 18 were 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 ii species diversity of damselfish recruits did not differ. This study shows that the effects of the presence of cleaner wrasse begin at recruitment. Although the presence of cleaner wrasse increases the abundance of recruiting damselfish, it is unclear what mechanism(s) are involved in this process. I conducted aquarium experiments to examine whether young P. amboinensis preferentially select a microhabitat that is adjacent to a cleaner wrasse. The study showed that both settlement-stage and juvenile P. amboinensis spend a greater proportion of time in a microhabitat adjacent to a cleaner wrasse than in one adjacent to a control wrasse (a non-cleaner wrasse, Halichoeres melanurus) or where no fish was present. More time was spent next to juvenile than adult cleaner wrasse. I then conducted field observations to determine if recruits that are in a 1 m radius of a juvenile cleaner wrasse receive any direct benefits (cleaning) and whether juvenile cleaner wrasse preferentially cleaned larger individuals. The size and identity of all fish that were cleaned within a 1 m radius of a cleaner were recorded, along with nearby non-cleaned conspecifics. I showed that only 2 % of the clients that a juvenile cleaner wrasse clean per 20 min observation were small recruits (< 20 mm, TL) whereas larger damselfishes comprised 58 % of clients. Juvenile cleaner wrasse also preferred to clean larger individuals than the median size of the surrounding nearby non-cleaned conspecifics. These results show that cleaner wrasse serve as a positive cue during microhabitat selection but that direct benefits to a small recruit are not obvious. The possibilities of indirect rather than direct (cleaning) benefits are discussed. I then used sentinel traps to investigate the cumulative number of gnathiid isopods infecting the ambon damselfish, Pomacentrus amboinensis, on patch reefs with and without cleaner wrasse. Previous studies may have under surveyed the number of gnathiids on a host related to the presence or absence of cleaner fish, due to the sampling techniques used (wired cages or handnets). As gnathiids are temporary parasites, they can drop off a host and return to the benthos before the fish is sampled; sentinel traps are able to retain such individuals. Nocturnal collections produced almost three times more gnathiids than diurnal collections. These results are consistent with previous studies. There was no difference in the number of gnathiids found in sentinel traps placed on reefs with and without a cleaner wrasse. These results appear initially to be at variance with the many advantages to fishes reported as being associated with the presence of L. dimidiatus. These observations lead to the novel hypothesis that the advantage to clients from cleaners is in the reduction in the length of parasitism rather than the number of infections being reduced. This research has provided important information regarding the parasites of damselfishes, from the starting point of the characterisation of the parasite fauna to how cleaning behaviour affects the ecology of recruiting fish, thus increasing our understanding of recruitment processes on coral reefs. My study has demonstrated that the richness of damselfishes exceeds that of their iii trematode parasites on the GBR although the parasite diversity (11 families) is remarkable. The work has contributed insight into both host range and species richness, having uncovered both novel trematode species, and novel hosts for known species. Regarding cleaning interactions, I have shown that 1) the abundance of damselfish recruits is higher on reefs with cleaner wrasse than on those without; 2) damselfish recruits preferentially select a microhabitat that is adjacent to a cleaner wrasse; and 3) that the benefits for young fish to be near cleaners are likely to be indirect rather than direct. These aspects of my study demonstrates the importance of cleaning mutualism not only for adult fishes, but for juvenile fishes during the recruitment period. iv Declaration by author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my research higher degree candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis. v Publications during candidature Sun D, Bray RA, Yong R, QY, Cutmore SC, Cribb TH (2014) Pseudobacciger cheneyae n. sp. (Digenea: Gymnophalloidea) from Weber’s chromis (Chromis weberi Fowler & Bean) (Perciformes: Pomacentridae) at Lizard Island, Great Barrier Reef, Australia. Systematic Parasitology 88:141-152 Sun D, Blomberg SP, Cribb TH, McCormick MI, Grutter AS (2012) The effects of parasites on the early life stages of a damselfish. Coral Reefs 31:1065-1075 Publications included in this thesis Incorporated as part of Chapter 2: Sun D, Bray RA, Yong R, QY, Cutmore SC, Cribb TH (2014) Pseudobacciger cheneyae n. sp. (Digenea: Gymnophalloidea) from Weber’s chromis (Chromis weberi Fowler & Bean) (Perciformes: Pomacentridae) at Lizard Island, Great Barrier Reef, Australia. Systematic parasitology 88:141-152 TH Cribb, RA Bray and SC Cutmore provided feedback and comments on the manuscript. R. Q-Y Yong provided editorial advice and assistance with specimen measurements. SC Cutmore assisted with phylogenetic analyses. D Sun collected and analysed the data and wrote the manuscript. vi Contributions by others to the thesis Chapter 1: TH Cribb provided feedback and comments. D Sun was responsible for the remainder of the work. Chapter 2: TH Cribb, RA Bray and R. Q-Y Yong provided feedback and comments on the manuscript. SC Cutmore assisted with phylogenetic analyses.