Dactylogyrids (Monogenoidea) parasitizing the gills of spinefoots (Teleostei: Siganidae): proposal of Glyphidohaptor n. gen., with two new species from the Great Barrier Reef, Australia, and G. plectocirra n. comb. from Ras Mohammed National Park, Egypt

Nine species of Siganus (Perciformes: Siganidae) were examined for dactylogyrids (Monogenoidea) from the Red Sea, Egypt; the Great Barrier Reef, Australia; and the South China Sea, China. Species of Tetrancistrum were found on siganids from all 3 localities; Pseudohaliotrema spp. were restricted to siganids from the Great Barrier Reef; and species representing Glyphidohaptor n. gen. were found on siganids from the Red Sea and Great Barrier Reef. Siganus argenteus from the Red Sea and Siganus vulpinus from the Great Barrier Reef were negative for dactylogyrid parasites. Glyphidohaptor n. gen. is proposed for 3 species (2 species new to science) and the new species are described: Glyphidohaptor phractophallus n. sp. from Siganus fuscescens from the Great Barrier Reef; Glyphidohaptor sigani n. sp. from Siganus doliatus (type host), Siganus punctatus, Siganus corallinus, and Siganus lineatus from the Great Barrier Reef; and Glyphidohaptor plectocirra (Paperna, 1972) n. comb. (= Pseudohaliotrema plectocirra Paperna, 1972) from Siganus luridus and Siganus rivulatus from the Red Sea.     

Trematodes of the Great Barrier Reef,Australia: emerging patterns of diversity and richness in coral reef fishes

The Great Barrier Reef holds the richest array of marine life found anywhere in Australia, including a diverse and fascinating parasite fauna. Members of one group, the trematodes, occur as sexually mature adult worms in almost all Great Barrier Reef bony fish species. Although the first reports of these parasites were made 100 years ago, the fauna has been studied systematically for only the last 25 years. When the fauna was last reviewed in 1994 there were 94 species known from the Great Barrier Reef and it was predicted that there might be 2,270 in total. There are now 326 species reported for the region, suggesting that we are in a much improved position to make an accurate prediction of true trematode richness. Here we review the current state of knowledge of the fauna and the ways in which our understanding of this fascinating group is changing. Our best estimate of the true richness is now a range, 1,100–1,800 species. However there remains considerable scope for even these figures to be incorrect given that fewer than one-third of the fish species of the region have been examined for trematodes. Our goal is a comprehensive characterisation of this fauna, and we outline what work needs to be done to achieve this and discuss whether this goal is practically achievable or philosophically justifiable.     

Coevolution of Retrovarium n. gen. (Digenea: Cryptogonimidae) in Lutjanidae and Haemulidae (Perciformes) in the Indo-West Pacific

We describe 11 new species of cryptogonimids belonging to Retrovarium n. gen., from eight species of Lutjanidae and one species of Haemulidae, from the Great Barrier Reef, French Polynesia and the Maldives. We also transfer Neoparacryptogonimus saccatus (Manter, 1963) and Neoparacryptogonimus sphericus Nahhas, Sey & Nishimoto, 1998 to Retrovarium. The morphologically based taxonomic approach was augmented with DNA sequence data from three nuclear ribosomal DNA regions (28S, ITS1 and ITS2) to explore the species integrity, biogeographic distribution and evolution of the species recognised here. Sequencing included multiple replicates and revealed 11 distinct genotypes which corroborated our morphologically based hypotheses of putative species present in the system. There was no intraspecific variation and all three rDNA regions differed between every combination of species. Two species exhibited wide geographic ranges, having identical rDNA sequences between the Great Barrier Reef and the Maldives, localities separated by over 9600 km. One host species, Symphorus nematophorus, proved to be exceptionally rich, harbouring six species. Minimum evolution analyses were conducted on each of the rDNA datasets independently; minimum evolution, maximum likelihood and Bayesian inference analyses were conducted on a combined (28S, ITS1 and ITS2) dataset for sequence comparison purposes and to explore the evolutionary history of these parasites. To examine the coevolutionary history of this complex, assessment of phylogenetic relationships between the 23 species of Lutjanidae and two species of Haemulidae collected during this survey was performed with data from 16S and cytochrome b mtDNA using Bayesian inference analysis. Despite the high host specificity observed in most of the species, mapping of the parasites on the host phylogeny revealed an absence of strict coevolution or co-descent within this complex. Overall, Retrovarium appears to have had an exceptionally patchy radiation, failing to infect many taxa, infecting species with no readily discernible pattern, and radiating dramatically within one species.     

Biogeography of tropical Indo-West Pacific parasites: A cryptic species of Transversotrema and evidence for rarity of Transversotrematidae (Trematoda) in French Polynesia

We sought transversotrematid trematodes from French Polynesian fishes by examining 304 individual scaled fishes of 53 species from seven families known to harbour the family elsewhere. A single species was found at two locations in the Tuamotus Archipelago on two species of Chaetodontidae (Chaetodon auriga and Chaetodon ephippium) and one species of Lutjanidae (Lutjanus gibbus). The species closely resembles Transversotrema borboleta Hunter & Cribb, 2012 from chaetodontids and lutjanids of the northern Great Barrier Reef (GBR) but differs from it consistently in 8 base positions of ITS2 rDNA. This level of variation exceeds that between some clearly morphologically distinct pairs of species of Transversotrema and the form from French Polynesia is thus interpreted as a distinct, though cryptic, species and named Transversotrema polynesiae n. sp. The new species forms part of a complex of species, here characterised as the T. borboleta complex, associated with chaetodontids and lutjanids in the tropical Indo-West Pacific. Most of the putative species within this complex are yet to be described. Comparison of identical numbers of matched samples of fishes from French Polynesia, Heron Island (southern GBR) and Lizard Island (northern GBR) revealed 1, 4 and 10 species of Transversotrema respectively suggesting that the French Polynesian fauna is depauperate for this family. In addition to those species apparently missing from suitable hosts in French Polynesia, several species from further west infect fishes (especially Nemipteridae) that are themselves absent from French Polynesia. This dramatic east–west decline in richness contrasts strongly with what is known for monogeneans, which appear to maintain their richness over the same scale, and is more precipitate than is known for other groups of trematodes. The decline might be explained in part by the absence of the as yet unknown first intermediate hosts in French Polynesia. However, we predict that it is explained by other life cycle traits. We hypothesise that the characters of large short-lived cercariae, short-lived miracidia, the absence in the life-cycle of second intermediate hosts that are capable of transporting the species, and definitive and first intermediate hosts that have limited vagility combine to give marine Transversotrematidae limited dispersal capacity and a propensity for localised speciation.     

Gene flow of Acanthaster planci (L.) in relation to ocean currents revealed by microsatellite analysis

Population outbreaks of the coral-eating starfish, Acanthaster planci , are hypothesized to spread to many localities in the Indo-Pacific Ocean through dispersal of planktonic larvae. To elucidate the gene flow of A. planci across the Indo-Pacific in relation to ocean currents and to test the larval dispersal hypothesis, the genetic structure among 23 samples over the Indo-Pacific was analysed using seven highly polymorphic microsatellite loci. The F -statistics and genetic admixture analysis detected genetically distinct groups in accordance with ocean current systems, that is, the Southeast African group (Kenya and Mayotte), the Northwestern Pacific group (the Philippines and Japan), Palau, the North Central Pacific group (Majuro and Pohnpei), the Great Barrier Reef, Fiji, and French Polynesia, with a large genetic break between the Indian and Pacific Oceans. A pattern of significant isolation by distance was observed among all samples ( P =  0.001, r  = 0.88, n  = 253, Mantel test), indicating restricted gene flow among the samples in accordance with geographical distances. The data also indicated strong gene flow within the Southeast African, Northwestern Pacific, and Great Barrier Reef groups. These results suggest that the western boundary currents have strong influence on gene flow of this species and may trigger secondary outbreaks.     

Latitudinal variation in coral communities in eastern Australia: a qualitative biophysical model of factors regulating coral reefs

The processes underlying the distributional limits of both corals and coral reefs can be elucidated by examining coral communities at high latitudes. Coral-dominated communities in eastern Australia cover a latitudinal range of >2,500 km, from the northern Great Barrier Reef (11°S) to South West Rocks (31.5°S). Patterns of coral species richness from 11 locations showed a clear separation between the Great Barrier Reef and subtropical sites, with a further abrupt change at around 31°S. Differences in community structure between the Great Barrier Reef and more southern sites were mainly attributable to higher cover of massive corals, branching Acropora, dead coral and coralline algae on the Great Barrier Reef, and higher cover of macroalgae and bare rock at more southern sites. The absence of some major reef-building taxa (i.e., staghorn Acropora and massive Porites) from most subtropical sites coincided with the loss of reef accretion capacity. Despite high cover of hard corals in communities at up to 31°S, only Lord Howe Island contained areas of reef accretion south of the Great Barrier Reef. Factors that have been hypothesized to account for latitudinal changes in coral community structure include water temperature, aragonite saturation, light availability, currents and larval dispersal, competition between corals and other biota including macroalgae, reduced coral growth rates, and failure of coral reproduction or recruitment. These factors do not operate independently of each other, and they interact in complex ways.     

Taxonomy, host specificity and dietary implications of Hurleytrematoides (Digenea: Monorchiidae) from chaetodontid fishes on the Great Barrier Reef

Five new and five previously described species of Hurleytrematoides are reported from 19 of 34 chaetodontid species examined from the Great Barrier Reef; new species are H. faliexae n. sp., H. galzini n. sp., H. loi n. sp., H. morandi n. sp., and H. sasali n. sp. Previously described species are H. coronatum, H. fijiensis, H. prevoti, H. bartolii, and H. zebrasomae. The genus is rediagnosed in the light of morphological variation of the new species; the degree of spination and shape of the terminal genitalia distinguish individual species. Species of Hurleytrematoides infect almost every clade of the family Chaetodontidae found on the Great Barrier Reef, but obligate corallivores are not infected. All ten species were found at Heron Island on the southern Great Barrier Reef, but only six at Lizard Island on the northern Great Barrier Reef. For three of the four species not present at Lizard Island, the absence appears to be statistically significant. Although all species are apparently restricted to chaetodontids on the GBR, specificity within the family varies from oioxenous to euryxenous; a core/satellite host paradigm explains the distribution of several species.     

Isolation by distance and vicariance drive genetic structure of a coral reef fish in the Pacific Ocean

We studied the genetic diversity of a coral reef fish species to investigate the origin of the differentiation. A total of 727 Acanthurus triostegus collected from 15 locations throughout the Pacific were analyzed for 20 polymorphic loci. The genetic structure showed limited internal disequilibrium within each population; 3.7% of the loci showed significant Hardy-Weinberg disequilibrium, mostly associated with Adh*, and we subsequently removed this locus from further analysis of geographic pattern. The genetic structure of A. triostegus throughout the tropical Pacific Ocean revealed a strong geographic pattern. Overall, there was significant population differentiation (multilocus F(ST) = 0.199), which was geographically structured according to bootstraps of neighbor-joining analysis on Nei's unbiased genetic distances and AMOVA analysis. The genetic structure revealed five geographic groups in the Pacific Ocean: western Pacific (Guam, Philippines, Palau, and Great Barrier Reef); central Pacific (Solomons, New Caledonia, and Fiji); and three groups made up of the eastern populations, namely Hawaiian Archipelago (north), Marquesas (equatorial), and southern French Polynesia (south) that incorporates Clipperton Island located in the northeastern Pacific. In addition, heterozygosity values were found to be geographically structured with higher values grouped within Polynesian and Clipperton populations, which exhibited lower population size. Finally, the genetic differentiation (F(ST)) was significantly correlated with geographic distance when populations from the Hawaiian and Marquesas archipelagos were separated from all the other locations. These results show that patterns of differentiation vary within the same species according to the spatial scale, with one group probably issued from vicariance, whereas the other followed a pattern of isolation by distance. The geographic pattern for A. triostegus emphasizes the diversity of the evolutionary processes that lead to the present genetic structure with some being more influential in certain areas or according to a particular spatial scale.     

Paradiscogaster flindersi and P. oxleyi n. sp. (Digenea: Faustulidae): overlapping host and geographical distributions in corallivore chaetodontid fishes in the tropical Indo-west Pacific

A total of 2,868 individuals of 47 species of chaetodontids were examined for faustulids at seven major localities in the Tropical Indo-West Pacific (TIWP). Combined morphological and molecular analyses allowed us to describe Paradiscogaster oxleyi n. sp. from three localities in the TIWP and in three host species, Chaetodon lunulatus Quoy & Gaimard (type-host), C. ornatissimus Cuvier and C. meyeri Bloch & Schneider. Molecular analysis of the ITS2 region of rDNA from two host species and three localities supports the morphology-based conclusion that P. oxleyi n. sp. is the same species at the three localities. Paradiscogaster flindersi Bray, Cribb & Barker, 1994 is reported from three new localities in the TIWP and is now known from 13 chaetodontid species. Sequences from samples consistent with P. flindersi differed from those from P. oxleyi n. sp. in 11–12 base pairs. The host ranges of the two species overlap broadly. Neither species was found in French Polynesia but both were found at Swain Reefs on the Great Barrier Reef. Only one of the two species was found at each of the five other sites. Both species occur almost exclusively in specialist corallivores allowing the inference that the metacercariae occur in corals. Finally, a key to the species of Paradiscogaster is provided.     

Ostracoda (Crustacea) from Lizard Island,northern Great Barrier Reef,Australia. II. The family Paradoxostomatidae Brady & Norman, 1889

The present paper deals with the taxonomy of the ostracod family Paradoxostomatidae Brady & Norman, 1889 from the coral reefs around Lizard Island, northern Great Barrier Reef, Australia. 18 species were found, all of them belonging to the genusParadoxostoma Fischer, 1855. 2 species had been previously described from Heron Island, southern Great Barrier Reef. 1 species had been described from the Red Sea. 2 species are left in open nomenclature.     

Two new blood flukes (Digenea: Sanguinicolidae) from Epinephelinae (Perciformes: Serranidae) of the Pacific Ocean

Pearsonellum pygmaeus n. sp. is described from Cromileptes altivelis (Serranidae), the Barramundi Cod, from Heron Island (southern Great Barrier Reef) and Lizard Island (northern Great Barrier Reef). This new species differs from Pearsonellum corventum (type and only species) in the combination of smaller overall body size, the relative distance of the brain from the anterior end, the relative lengths of both the oesophagus and the testis, the degree to which the testis extends outside the intercaecal field, the shape of the testis, the shape and size of the ovary and the extent to which the uterus loops around the ovary. There are in addition, 20 base pair differences between the ITS2 rDNA sequence of P. pygmaeus n. sp. and that of P. corventum. Three new host records for P. corventum are reported. Adelomyllos teenae n. g., n. sp. is described from Epinephelus coioides (Serranidae), the Estuary Cod, from Moreton Bay, southeast Queensland. The new genus differs from the 22 other sanguinicolid genera in the combined possession of two testes, a cirrus-sac, separate genital pores, a post-ovarian uterus and an H-shaped intestine. A. teenae n. sp. is the third sanguinicolid described from the Epinephelinae. Sanguinicolids have now been reported from 11 species of Serranidae.     

Two new species of Prosorhynchoides (Digenea: Bucephalidae) from Tylosurus crocodilus (Belonidae) from the great barrier reef and French Polynesia

We surveyed 14 individuals of Tylosurus crocodilus Péron & Lesueur 1821 (Belonidae) collected from the waters around Lizard Island and Heron Island, Great Barrier Reef, Queensland, Australia, and the waters around Moorea, French Polynesia. We describe two new species of bucephaline trematodes from them, Prosorhynchoides galaktionovi n. sp. and P. kohnae n. sp. They are morphologically distinct from existing Prosorhynchoides spp., with molecular data from 28S and ITS-2 ribosomal DNA, as well as cox1 mitochondrial DNA, further supporting our morphological findings. Neither species has been observed in other belonid fishes. The new species fall into the clade of species of Prosorhynchoides from belonids previously identified in Australian waters. These findings strengthen the observation that groups of bucephaline species have radiated, at least in part, in tight association with host taxa. There are now five species of Prosorhynchoides known from two belonid species in Australian waters. We, therefore, predict further richness in the nine other belonid species present.     

Habitat selection and aggression as determinants of spatial segregation among damselfish on a coral reef

Adults of many closely related coral reef fish species are segregated along gradients of depth or habitat structure. Both habitat selection by new settlers and subsequent competitive interactions can potentially produce such patterns, but their relative importance is unclear. This study examines the potential roles of habitat selection and aggression in determining the spatial distribution of adults and juveniles of four highly aggressive damselfishes at Lizard Island, northern Great Barrier Reef. Dischistodus perspicillatus, D. prosopotaenia, D. melanotus, and D. pseudochrysopoecilus maintain almost non-overlapping distributions across reef zones, with adults of one species dominating each reef zone. Juveniles exhibit slightly broader distributional patterns suggesting that subsequent interactions reduce overlap among species. Although habitat choice experiments in aquaria suggest that associations between juveniles and substrata types in the field are partly due to habitat selection, large overlaps in the use of substrata by the different species were also found, suggesting that substratum selection alone is insufficient in explaining the discrete spatial distributions of adults. The strength of aggressive interactions among all four species was tested by a "bottle" experiment, in which an adult or juvenile of each species was placed in the territories of adult fish on the reef. The greatest levels of interspecific aggression were directed against adults and juveniles of neighbouring species. The highest levels of aggression were associated with species exhibiting the greatest levels of overlap in resource use. Evidently both habitat selection and interspecific aggression combine to determine the adult distributions of these species.     

Reef Fishes in Biodiversity Hotspots Are at Greatest Risk from Loss of Coral Species

Coral reef ecosystems are under a variety of threats from global change and anthropogenic disturbances that are reducing the number and type of coral species on reefs. Coral reefs support upwards of one third of all marine species of fish, so the loss of coral habitat may have substantial consequences to local fish diversity. We posit that the effects of habitat degradation will be most severe in coral regions with highest biodiversity of fishes due to greater specialization by fishes for particular coral habitats. Our novel approach to this important but untested hypothesis was to conduct the same field experiment at three geographic locations across the Indo-Pacific biodiversity gradient (Papua New Guinea; Great Barrier Reef, Australia; French Polynesia). Specifically, we experimentally explored whether the response of local fish communities to identical changes in diversity of habitat-providing corals was independent of the size of the regional species pool of fishes. We found that the proportional reduction (sensitivity) in fish biodiversity to loss of coral diversity was greater for regions with larger background species pools, reflecting variation in the degree of habitat specialization of fishes across the Indo-Pacific diversity gradient. This result implies that habitat-associated fish in diversity hotspots are at greater risk of local extinction to a given loss of habitat diversity compared to regions with lower species richness. This mechanism, related to the positive relationship between habitat specialization and regional biodiversity, and the elevated extinction risk this poses for biodiversity hotspots, may apply to species in other types of ecosystems.     

Spatial patterns in abundance of a damselfish reflect availability of suitable habitat

For species with metapopulation structures, variation in abundance among patches can arise from variation in the input rate of colonists. For reef fishes, variability in larval supply frequently is invoked as a major determinant of spatial patterns. We examined the extent to which spatial variation in the amount of suitable habitat predicted variation in the abundance of the damselfish Dascyllus aruanus, an abundant planktivore that occupies live, branched coral throughout the Indo-Pacific. Reef surveys established that size, branching structure and location (proximity to sand) of the coral colonies together determined the ”suitability” of microhabitats for different ontogenetic stages of D. aruanus. Once these criteria were known, patterns of habitat use were quantified within lagoons of five Pacific islands. Availability of suitable habitat generally was an excellent predictor of density, and patterns were qualitatively consistent at several spatial scales, including among different lagoons on the same island, among different islands and between the central (French Polynesia and Rarotonga) and western (Great Barrier Reef, Australia) South Pacific. A field experiment that varied the amount of suitable coral among local plots indicated that habitat for settlers accounted for almost all of the spatial variation in the number of D. aruanus that settled at that location, suggesting that spatial patterns of abundance can be established at settlement without spatial variation in larval supply. Surveys of four other species of reef-associated fish revealed that a substantial fraction of their spatial variation in density also was explained by availability of suitable reef habitat, suggesting that habitat may be a prevalent determinant of spatial patterns. The results underscore the critical need to identify accurately the resource requirements of different species and life stages when evaluating causes of spatial variation in abundance of reef fishes. Received: 18 May 1999 / Accepted: 9 January 1999     

Reductions in the mitochondrial DNA diversity of coral reef fish provide evidence of population bottlenecks resulting from Holocene sea-level change

This study investigated the influence of reproductive strategy (benthic or pelagic eggs) and habitat preferences (lagoon or outer slope) on both diversity and genetic differentiation using a set of populations of seven coral reef fish species over different geographic scales within French Polynesia. We hypothesized that a Holocene sea-level decrease contributed to severe reduction of population size for species inhabiting lagoons and a subsequent decrease of genetic diversity. Conversely, we proposed that species inhabiting stable environments, such as the outer slope, should demonstrate higher genetic diversity but also more structured populations because they have potentially reached a migration-genetic drift equilibrium. Sequences of the 5' end of the mitochondrial DNA (mtDNA) control region were compared among populations sampled in five isolated islands within two archipelagos of French Polynesia. For all the species, no significant divergences among populations were found. Significant differences in mtDNA diversity between lagoonal and outer-slope species were demonstrated both for haplotype diversity and sequence divergence but none were found between species with different egg types. Pairwise mismatch distributions suggested rapid population growth for all the seven species involved in this study, but they revealed different distributions, depending on the habitat preference of the species. Although several scenarios can explain the observed patterns, the hypothesis of population size reduction events relative to Holocene sea-level regression and its consequence on French Polynesia coral reefs is the most parsimonious. Outer-slope species have undergone a probable weak and/or old bottleneck (outer reefs persisted during low sea level, leading to reef area reductions), whereas lagoonal species suffered a strong and/or recent bottleneck since Holocene sea-level regression resulted in the drying out of all the atolls that are maximum 70 meters deep. Since present sea level was reached between 5000 and 6000 years ago, different demographic events (bottlenecks or founder events) have lead to the actual populations of lagoons in French Polynesia.     

Large scale spatial and temporal variation in recruitment to fish populations on coral reefs

Summary Visual census was used to sample young of the year of fish species recruited to each of two habitats on seven lagoonal platform reefs of the Capricorn-Bunker Group, Great Barrier Reef. The reefs sampled span an area 70 km in extent. In 1983, 62 species from 13 families were detected as recruits on reef slope sites. The total number of cruits, and the number of each of 6 of 16 species tested, differed significantly among reefs, despite the fact that differences among sites within reefs did not exist, and that sampled slopes were chosen to be hydrographically, and physiographically as similar as possible. Lagoonal patch reefs were sampled in two years. In 1982, 76 species of 11 families occurred as recruits. In 1983, 86 species of 12 families were recorded. All of 22 species common enough to test showed some significant variation in abundance among reefs, years, or both. For 9 species, significant year x reef interactions occurred, demonstrating that relative recruitment success among reefs varied between years. Reasons for the substantial levels of variability are discussed, and implications for the organisation of reef fish communities are considered.     

Characterization and isolation of DNA microsatellite primers in the cardinalfish (Apogon doederleini)

Proper management of reef areas depends greatly on understanding the degree of dispersal of each species involved. The larvae of most reef fishes disperse from the natal reef before or soon after hatching and return to the reef environment after a pre‐settlement stage of several days to weeks. We characterized eight polymorphic microsatellite loci for the cardinal fish Apogon doederleini to study the spatial scale of connectivity of populations of different reefs of the Great Barrier Reef, Australia.     

Pomphorhynchus heronensis and restricted movement of Lutjanus carponotatus on the Great Barrier Reef

Samples of Lutjanus carponotatus (Lutjanidae) from reef flat (shallow) and reef slope (deep) sites around Heron and Wistari reefs on the southern Great Barrier Reef were examined for Pomphorhynchus heronensis (Acanthocephala). Individual fish from the reef slope had 0-9 (2.6) worms as compared with 1-122 (39.6) worms for individuals from the reef flat (P < 0.0001). Other variables (year, season, size of fish) made little contribution to the variation. Reef flat and reef slope sites were separated by as little as 300 m. These results imply both that the fish have very limited local movement and that transmission of the parasite is concentrated locally.