Spatial and Temporal Variations of the Ectoparasites of Seven Reef Fish Species from Lizard Island and Heron Island, Australia
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MARINE ECOLOGY PROGRESS SERIES Vol. 115: 21-30,1994 Published December 1 Mar. Ecol. Prog. Ser. Spatial and temporal variations of the ectoparasites of seven reef fish species from Lizard Island and Heron Island, Australia Alexandra S. Grutter Department of Marine Biology, James Cook University of North Queensland, Townsville, Queensland 4811. Australia ABSTRACT: Spat~aland temporal variations in abundance of ectoparasites from 7 coral reef fish species [Hemigyrnnus melapterus (Labridae), Siganus doliatus (Siganidae), Scolopsis bilinea tus (Nemipteridae), Thalassoma lunare (Labridae), Scarus sordidus (Scaridae), Ctenochaetus stn'atus (Acanthuridae),and Acanthochromis polyacanthus (Pomacentridae)]at 2 locations, Lizard Island and Heron Island in the Great Barner Reef, were investigated. The study demonstrates that there is a significant species-specific parasite fauna wh~chis conserved over space and time. Host identity explained most of the variation in parasite composition and abundance while host size explained a smaller proportion of the variation. For each species the parasite assemblage showed little variation among local, but physically varied, sites. Species-specific patterns of parasite abundance were similar between widely separated locations, although there were more categories of parasites at the northern locat~on,Lizard Island. Parasite numbers and species composition among fish species at Lizard Island d~dnot vary anlong collection times except for S. doliatus, which had a 7-fold increase between May 1992 and January 1993, mainly due to dactylogyridean monogeneans. Parasite abundance was positively correlated with fish standard length for 3 fish species. KEY WORDS: Ectoparasites . Coral reef fish. Spatial variation . Temporal variation . Great Barrier Reef INTRODUCTION knowledge of the spatial variability among sites will determine whether sampling can be reduced to par- The numbers and species composition of marine ticular sites or comblned among sites. ectoparasites vary both among and within fish species. Information on the temporal variability of parasites is Variation in parasites within a species can occur on a needed to establish whether observed parasite fauna is small spatial scale (Yeo & Spieler 1980) or on a large representative of overall parasite fauna. Temporal spatial scale latitudinally (Dogiel 1961, Polyanski 1961b, variability in parasites can also affect the factors they Rohde 1977). Parasites also vary seasonally (Kennedy influence. For instance, the diet of cleaner fish or the 1975) and as a function of host size (Bortone et al. 1978). cleaning behavior of fish hosts could change if the These sources of variation can confound results and parasite loads of fish change over time. Studies of therefore must be considered in parasitological studies. temporal variation in fish parasites have been largely Estimates of spatial variation are needed when confined to cold temperate seas (Llewellyn 1959, designing sampling programs in order to obtain reli- Noble et al. 1963, Kennedy 1975, Rawson 1976), with able estimates of parasites. Before large-scale spatial the few studies in the tropics restricted mostly to the comparisons among locations can be made, estimates parasites of snails (Rohde & Sandland 1973, Cannon of small-scale spatial variation among sites are needed 1978, 1979, Rohde 1981). to avoid confounding effects. Estimates of small-scale The diversity of coral reef fishes found in the Great variation are also important if fish collections are logis- Barrier Reef is high (Randall et al. 1990). The diversity tically constrained. For example, if some fish species of monogenean parasites in the Great Barrier Reef is are more easily collected at some sites than others, almost certainly greater than that of fish species O Inter-Research 1994 Resale of full article not permitted 22 Mar Ecol. Prog. Ser. 115: 21.L30, 1994 (Rohde 1977) and the number of parasite species at 7 m) and have different levels of wave exposure. Site 1 Heron Island alone has been estimated at 20 000 (North Point) is the most exposed, Site 2 (Granite Bluff) (Rohde 1977). If both parasite fauna and flsh are is less exposed, and Site 3 (Lagoon)is in a protected la- diverse, the potential for variability in the interactions goon behind a small island and has little wave exposure. between fish and parasites is high. Such questions The differences among sites are reflected in the fish require estimates of how parasites vary amongst fauna (Choat & Bellwood 1985). species and the degree to which they are constant over Lizard Island (14" 40' S, 145" 26' E) and Heron Island space and time. This information is relevant not only (23" 27' S, 151" 55' E) are approximately 1000 km for this type of study, but also for other parasitological apart, with Lizard Island located in the northern part work such as in fish stock discrimination (Lester et of the Great Barrier Reef and Heron Island in the al. 1988) and evolution (Brooks & McLennan 1993). southern part. Lizard Island is a continental island with Much parasitological work is observational or de- fringing reefs while Heron Island is a coral cay with scriptive and thus tends to be non-quantitative (Sinder- a large platform reef. The locations were selected mann 1986).This study is quantitative rather than qual- because they represent reef systems at the extremes of itative with the emphasis placed on measuring the the Great Barrier Reef, yet both have the species inves- variability in numbers of parasites using broad cate- tigated. Fish were collected at 3 times (seasons) from gories of ectoparasites. The complete ectoparasite fau- Lizard Island (May 1992, August 1992, and January nas of 7 relatively small fish species which are common 1993) and once from Heron Island (June 1993). on coral reefs of the Great Barrier Reef are quantified. Sites. To investigate the number and composition of The variations in ectoparasite numbers and species parasites (Table 1) among fish species collected from composition among fish species, sites, locations, and different sites, 5 to 9 fish per site from 3 sites were times of collection, as well as the relationship between collected from each species in May 1992. Specimens of host size and parasite abundance, were investigated. The species span a range of taxonomic and ecological but Table 1. Parasite categories and codes used for classifying ectoparasites from 7 coral reef fishes. Bold headings are broad descnptions of categories. are all common in shallow coral reef waters. See 'Materials and methods' for details on species This study forms part of broader study on the feeding biology of cleaner fish. Size range Copepoda MATERIALS AND METHODS Hatscheha hemigymni 280 pm to 1 mm Hatschekla sp a 1.9 to 2.3 mm Bomo Acanthocolax sp. nov. males and/or The fish species investigated were Hemi- Orbitacolax sp. nov. males gymnus rnelapterus (Labridae), Siganus Orbi Orbitacolax sp. nov. females doliatus (Siganidae), Scolopsis bilineatus Acan Acanthocolax sp. nov. females (Nemipteridae), Thalassoma lunare (Labri- Cali Caliginae spp. dae), Scarus sordidus (Scaridae), Cteno- CalL Caligidae larvae chaetus striatus (Acanthuridae),and Acan- Naup Nauplii thochromis polyacanthus (Pomacentridae). UCop Unidentified spp. The species were selected because they Isopoda live in similar hab~tatsand are relatively Gnat Gnathia spp larvae abundant and easy to capture. All species lsop Anilocra nemipteri and Anilocra sp, juv. have different feeding habits, and 3 (H. Monogenea melapterus, T. lunare, S. sordidus) are taxo- Anop Anoplodiscus spp. nomically related and belong to the order Bene Benedininae spp. Dact Dactylogyridea spp. Labroidei (sensu Greenwood et al. 1966). A total of 304 fish were collected. Digenea TraL Transversotrema licin urn Sampling design. Spatial variation was TraH Transversotrema haasi examined at 2 scales, within a reef system Tran Transversotrema spp (L~zardIsland) incorporating different habi- UDig Other unidentlf~edspp. tats and between reef systems separated by Turbellaria 1000 km (Lizard Island and Heron Island). Turb Ichthyophaga and/or Paravortex spp. Small-scale variation was examined at 3 Platyhelminthes sites (1 to 5 km apart) located around Lizard UFla Unidentified flatworms Island which are in shallow coral reefs (2 to Grutter. Variations among ectoparasites of seven Austral~anreef fish species 23 approximately similar size were collected from within variate analysis of variance (MANOVA) was used a species to reduce variation due to host size. to test for differences in the number of parasites per Locations. The number and composition of parasites category among species and sites and among species (Table 1) among fish collected at 2 locations were and locations; a single-factor MANOVA was used to examined. The collections at Lizard Island (January test for differences in the number of parasites per par- 1993) were from the above 3 sites. The collections at asite category among times for each of the 2 species. Heron Island (June 1993) were from 2 sites on the reef All Transversotrema spp. at Heron Island were pooled slope (2 to 10 m in depth) located on opposite sides of to increase the degrees of freedom in the MANOVA. the island (2 km apart). Between 5 and 9 specimens To discriminate among species and sites and among were collected from the 7 species at each location. species and locations a canonical discriminant analysis Sites at both locations were combined as the sample (CDA) was used. The multivariate test statistic, Pillai's sizes of fish from both locations were too small and Trace, was used in all MANOVAs because it is more unbalanced to test for differences anlong sites. robust to heterogeneity of variance and is less likely Time. The number of parasites per fish on Hemigym- to involve Type I error than comparable tests (Green nus melapterus and ThaJassoma lunare was analyzed 1979). To satisfy the assumptions of the statistical for differences among 3 collection times (seasons) at analyses performed, all data were natural-log(x+l) Lizard Island (May 1992, August 1992, January 1993). transformed to achieve homogeneity of variance or lin- The remaining 5 species were tested for differences earity.