Measuring aggregation in parasite populations.

Aggregation, a fundamental feature of parasite distributions, has been measured using a variety of indices. We use the definition that parasite-host system A is more aggregated than parasite-host system B if any given proportion of the parasite population is concentrated in a smaller proportion of the host population A than of host population B. This leads to indices based on the Lorenz curve such as the Gini index (Poulin's D), coefficient of variation and the Hoover index, all of which measure departure from a uniform distribution. The Hoover index is particularly useful because it can be interpreted directly in terms of parasites and hosts. An alternative view of aggregation is degree of departure from a Poisson (or random) distribution, as used in the index of dispersion and the negative binomial k. These and Lloyd's mean crowding index are reinterpreted and connected back to Lorenz curves. Aggregation has occasionally been defined as the slope from Taylor's law, although the slope appears unrelated to other indices. The Hoover index may be the method of choice when data points are available, and the coefficient of variation when only variance and mean are given.

Does moving up a food chain increase aggregation in parasites?

General laws in ecological parasitology are scarce. Here, we evaluate data on numbers of fish parasites published by over 200 authors to determine whether acquiring parasites via prey is associated with an increase in parasite aggregation. Parasite species were grouped taxonomically to produce 20 or more data points per group as far as possible. Most parasites that remained at one trophic level were less aggregated than those that had passed up a food chain. We use a stochastic model to show that high parasite aggregation in predators can be solely the result of the accumulation of parasites in their prey. The model is further developed to show that a change in the predators feeding behaviour with age may further increase parasite aggregation.

Parasites as valuable stock markers for fisheries in Australasia, East Asia and the Pacific Islands.

Over 30 studies in Australasia, East Asia and the Pacific Islands region have collected and analysed parasite data to determine the ranges of individual fish, many leading to conclusions about stock delineation. Parasites used as biological tags have included both those known to have long residence times in the fish and those thought to be relatively transient. In many cases the parasitological conclusions have been supported by other methods especially analysis of the chemical constituents of otoliths, and to a lesser extent, genetic data. In analysing parasite data, authors have applied multiple different statistical methodologies, including summary statistics, and univariate and multivariate approaches. Recently, a growing number of researchers have found non-parametric methods, such as analysis of similarities and cluster analysis, to be valuable. Future studies into the residence times, life cycles and geographical distributions of parasites together with more robust analytical methods will yield much important information to clarify stock structures in the area.

Parasites as indicators of movement and population connectivity of a non-diadromous, tropical estuarine teleost: king threadfin Polydactylus macrochir.

Temporal and spatial patterns in parasite assemblages were examined to evaluate the degree of movement and connectivity of post-recruitment life-history stages of a large, non-diadromous tropical estuarine teleost, king threadfin Polydactylus macrochir, collected from 18 locations across northern Australia. Ten parasites types (juvenile stages of two nematodes and seven cestodes, and adults of an acanthocephalan) were deemed to be suitable for use as biological tags, in that they were considered to have a long residence time in the fish, were relatively easy to find and were morphologically very different to each other which aided discrimination. Univariate and discriminant function analysis of these parasites revealed little difference in temporal replicates collected from five locations, suggesting that the parasite communities were stable over the timeframes explored. Univariate, discriminant function, and Bray-Curtis similarity analyses indicated significant spatial heterogeneity, with Bray-Curtis classification accuracies ranging from 55 to 100% for locations in north-western and northern Australia, 24 to 88% in the Gulf of Carpentaria, and 39 to 88% on the east coast of Queensland. Few differences were observed among locations separated by <200 km. The observed patterns of parasite infection are in agreement with concurrent studies of movement and connectivity of P. macrochir in that they indicate a complex population structure across northern Australia. These results should be considered when reviewing the management arrangements for this species.

Overdispersion in marine fish parasites.

A modification of Taylor's Power law was used to compare the degree of overdispersion in frequency distributions from 38 datasets of marine parasites, data that had originally been collected for fish stock discrimination. The results strongly indicate that the overriding factor contributing to overdispersion in these helminths and crustaceans is the number of hosts in the life cycle. This was particularly well shown by juveniles of Anisakis 1 from different fish species. Data on the cestode Otobothrium cysticum and the monogenean Pricea multae appear anomalous and lead to conclusions about their biology not at first evident from the literature.

Genetic population structure of grey mackerel Scomberomorus semifasciatus in northern Australia.

This study used mtDNA sequence and microsatellite markers to elucidate the population structure of Scomberomorus semifasciatus collected from 12 widespread sampling locations in Australia. Samples (n = 544) were genotyped with nine microsatellite loci, and 353 were sequenced for the control (384 bp) and ATPase (800 bp) mtDNA gene regions. Combined interpretation of microsatellite and mtDNA data identified four genetic stocks of S. semifasciatus: Western Australia, north-west coast of the Northern Territory, Gulf of Carpentaria and the eastern coast of Queensland. Connectivity among stocks across northern Australia from the Northern Territory to the eastern coast of Queensland was high (mean F(ST) = 0·003 for the microsatellite data and Φ(ST) = 0·033 and 0·009 for control region and ATPase, respectively) leading to some uncertainty about stock boundaries. In contrast, there was a clear genetic break between the stock in Western Australia compared to the rest of northern Australia (mean F(ST) = 0·132 for the microsatellite data and Φ(ST) = 0·135 and 0·188 for control region and ATPase, respectively). This indicates a restriction to gene flow possibly associated with suboptimal habitat along the Kimberley coast (north Western Australia). The appropriate scale of management for this species corresponds to the jurisdictions of the three Australian states, except that authorities in Queensland and Northern Territory should co-ordinate the management of the Gulf of Carpentaria stock.

Stock structure of blue threadfin Eleutheronema tetradactylum across northern Australia, as indicated by parasites.

The parasite fauna of the blue threadfin Eleutheronema tetradactylum, collected from 14 sites across northern Australia, was examined to evaluate the degree of movement and subsequent stock structure of the fish. Univariate and multivariate analysis of nine 'permanent' parasite species [the nematodes Anisakis (type I) and Terranova (type II), the cestodes Otobothrium australe, Pterobothrium pearsoni, Pterobothrium sp. A, Callitetrarhynchus gracilis, Parotobothrium balli and Nybelinia sp., and the acanthocephalan Pomphorhynchus sp.] demonstrated little similarity between sites, indicating limited mixing and therefore long-term separation of post-juvenile fish. As such, the effects of fishing are likely to be localized within the current administrative boundaries, implying little need for interstate co-operative management. Within each jurisdiction, management of E. tetradactylum populations, including the establishment of harvest strategies and fishery regulations, should be conducted in a way that recognizes the resident nature of the fish.

Stock structure of blue threadfin Eleutheronema tetradactylum on the Queensland east coast, as determined by parasites and conventional tagging.

Blue threadfin Eleutheronema tetradactylum (Polynemidae) were examined from four areas (Princess Charlotte Bay, Trinity Inlet, Halifax Bay and Upstart Bay) in eastern Queensland covering a distance of c. 950 km of coastline. Parasites were used as biological markers to infer stock structure of E. tetradactylum. Parasites designated as 'temporary' biological markers were the copepod Thysanote eleutheronemi, the acanthocephalan Neoechinorhynchus topseyi, the nematode Philometra rajani and hemiurid trematodes. The larval nematodes Anisakis sp. Type 1 and Terranova sp. Type 2; and the larval cestodes Pterobothrium pearsoni and Callitetrarhynchus gracilis were considered 'permanent' biological markers. Both univariate and multivariate analyses demonstrated that there was little difference in temporary parasite abundance between the four areas. In contrast, the same analyses revealed that most areas had two or more significant differences in permanent parasite abundance, with the exception of Halifax Bay and Upstart Bay, which were significantly different only in the multivariate analysis. Biological markers predicted that Princess Charlotte Bay and Trinity Inlet consisted of distinct populations, whereas Halifax Bay and Upstart Bay were not clearly differentiated. Tag recapture data supported this hypothesis; the majority of recaptures were within 100 km of the initial tagging location. Geographical movement of E. tetradactylum may be limited due to their biology and ecology, as well as the distances and oceanographic boundaries that separate habitats. Contrary to current management definitions, the stock structure of E. tetradactylum on the east coast of Queensland appears to be geographically differentiated at a small spatial scale.

Detection of the initial infective stages of the protozoan parasite Marteilia sydneyi in Saccostrea glomerata and their development through to sporogenesis.

DNA probes were used in in situ hybridisation on histological sections of oysters exposed for defined intervals to Marteilia sydneyi infection to reveal the early development of the parasite in the oyster host, Saccostrea glomerata. The initial infective stages enter through the palps and gills whereupon extrasporogonic proliferation results in the liberation of cells into surrounding connective tissue and haemolymph spaces. Following systemic dissemination, the parasite infiltrates the digestive gland and becomes established as a nurse cell beneath the epithelial cells in a digestive tubule. Here, cell-within-cell proliferation results in the eventual liberation of daughter cells from the nurse cell into spaces between adjacent epithelial cells. None of these stages had previously been described. Proliferation is associated with host responses, including haemocytic infiltration of the connective tissue and diapedesis across tubule epithelia. The responses cease as sporogenesis begins.

Recent advances in our knowledge of the Myxozoa.

In the last few years two factors have helped to significantly advance our understanding of the Myxozoa. First, the phenomenal increase in fin fish aquaculture in the 1990s has lead to the increased importance of these parasites; in turn this has lead to intensified research efforts, which have increased knowledge of the development, diagnosis. and pathogenesis of myxozoans. The hallmark discovery in the 1980s that the life cycle of Myxobolus cerebralis requires development of an actinosporean stage in the oligochaete. Tubifex tubifex, led to the elucidation of the life cycles of several other myxozoans. Also, the life cycle and taxonomy of the enigmatic PKX myxozoan has been resolved: it is the alternate stage of the unusual myxozoan, Tetracapsula bryosalmonae, from bryozoans. The 18S rDNA gene of many species has been sequenced, and here we add 22 new sequences to the data set. Phylogenetic analyses using all these sequences indicate that: 1) the Myxozoa are closely related to Cnidaria (also supported by morphological data); 2) marine taxa at the genus level branch separately from genera that usually infect freshwater fishes; 3) taxa cluster more by development and tissue location than by spore morphology; 4) the tetracapsulids branched off early in myxozoan evolution, perhaps reflected by their having bryozoan, rather than annelid hosts; 5) the morphology of actinosporeans offers little information for determining their myxosporean counterparts (assuming that they exist); and 6) the marine actinosporeans from Australia appear to form a clade within the platysporinid myxosporeans. Ribosomal DNA sequences have also enabled development of diagnostic tests for myxozoans. PCR and in situ hybridisation tests based on rDNA sequences have been developed for Myxobolus cerebralis, Ceratomyxa shasta, Kudoa spp., and Tetracapsula bryosalmonae (PKX). Lectin-based and antibody tests have also been developed for certain myxozoans, such as PKX and C. shasta. We also review important diseases caused by myxozoans, which are emerging or re-emerging. Epizootics of whirling disease in wild rainbow trout (Oncorhynchus mykiss) have recently been reported throughout the Rocky Mountain states of the USA. With a dramatic increase in aquaculture of fishes using marine netpens, several marine myxozoans have been recognized or elevated in status as pathological agents. Kudoa thyrsites infections have caused severe post-harvest myoliquefaction in pen-reared Atlantic salmon (Salmo salar), and Ceratomyxa spp., Sphaerospora spp., and Myxidium leei cause disease in pen-reared sea bass (Dicentrarchus labrax) and sea bream species (family Sparidae) in Mediterranean countries.

Anti-immunoglobulin antisera used in an ELISA to detect antibodies in barramundi Lates calcarifer to Cryptocaryon irritans.

Immunoglobulins (Ig) in serum from barramundi vaccinated with bovine serum albumin (BSA) were purified by ammonium sulphate precipitation and affinity chromatography using BSA as the ligand. The BSA-binding activity of eluted putative Ig fractions was assessed by enzyme-linked immunosorbent assay (ELISA) before being pooled and characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Double affinity purification did not improve the purity of the Ig preparation compared to single affinity purification. Barramundi Ig were injected into sheep to produce anti-Ig antisera which were assessed in an indirect ELISA as the secondary antibody to detect serum Ig in barramundi vaccinated with Cryptocaryon irritans theronts. Affinity-purified Ig induced a more specific reagent for use as secondary antibody in ELISA than did normal whole-barramundi sera. The heavy (H) chain of barramundi Ig had an apparent molecular weight of 70 kDa while that of the light (L) chain was 27 kDa in SDS-PAGE studies. Under non-reducing conditions 2 putative populations of Ig were identified, at 768 and 210 kDa. The N-terminal sequence of the barramundi Ig H chain showed 78% homology with channel catfish Ictalurus punctatus Ig H chain sequence.

Actinosporeans (Myxozoa) with four developing spores within a pansporocyst: Tetraspora discoidea n.g. n.sp. and Tetraspora rotundum n.sp.

Two species of marine actinosporeans with spores that develop in groups of four rather than eight within a pansporocyst are described. In other respects, including triradial symmetry, three polar capsules each enclosing a coiled polar filament, parasitic in invertebrates, they conform with other actinosporeans. Both new species were found in the coelom of tubificid oligochaetes collected from Moreton Bay, Queensland, Australia. Spores of Tetraspora discoidea n.g. n.sp. are disc-like, almost round in apical view and dorso-ventrally compressed in side view, whereas spores of Tetraspora rotundum n.sp. are spherical. The novel development of these two marine actinosporeans may signify other variations in the life-cycles of marine Myxozoa.

Actinosporeans (Myxozoa) from marine oligochaetes of the Great Barrier Reef.

Four species of actinosporeans are described from marine oligochaetes (all Tubificidae) from the Great Barrier Reef, Queensland, Australia. They developed in the coelom of the oligochaete and produced spores in groups of eight in the pansporocysts. The new genus Endocapsa is proposed within the family Sphaeractinomyxidae Janiszewska, 1957 on the basis that mature spores have small valve cell processes and non-protruding polar capsules. The type-species, Endocapsa rosulata n. sp., has three valve cell processes, which resemble a rosette, and submerged polar capsules. It infected Heterodrilus cf. keenani from Heron Island and morphologically similar parasites occurred in Thalassodrilides cf. gurwitschi and Heronidrilus sp. from Lizard Island. E. stepheni n. sp. has asymmetrical valve cell processes and submerged polar capsules. It was found in H. cf. keenani and H. queenslandicus from Heron Island. Sphaeractinomyxon leptocapsula n. sp. has thin widely spaced polar capsules and is described from Heronidrilus sp. from Lizard Island. S. ersei Hallett, O'Donoghue & Lester, 1998 infected Tubificidae gen. sp. from Heron Island and S. cf. ersei occurred in Bathydrilus sp., Thalassodrilides cf. gurwitschi and Limnodriloides lateroporus from Lizard Island.

The (dis)embodied self in anorexia nervosa.

This paper deconstructs the debate that has been raging for over a decade between proponents of the feminist cultural model of eating disorders and supporters of the traditional medical model of illness and treatment, bringing the level of analysis one step deeper-to the question of the constructions of "the self" employed in these discourses and the implications of these constructions for the successful understanding and treatment of anorexia nervosa. The paper argues that while feminist theorizing has largely dislodged the current representations of anorexia nervosa from the clamps of myopic medical discourses devoid of detailed cultural analysis, it has in fact produced similar theoretical dichotomies and blind spots that preclude the successful theorizing of an embodied self and its particular articulation in anorexia nervosa. It is proposed here that Foucault's [(1986) The Care of the Self. The History of Sexuality, Vol. 3. Vintage, New York] notion of "technologies of the self" can provide us with a useful tool for bridging the split between the "inside" and "outside" produced and reified in both the medical model and the feminist cultural formulation of anorexia; a framework is suggested for the implementation of this interpretative position, based on a reconceptualization of the particular ritualistic behaviors associated in anorexia as articulating the core issues of the illness-a reconfiguration and repositioning of the "inside" and the "outside" as a means of tailoring the self along a particular line of "attitude". The essay is based on eight months of fieldwork counseling in an eating disorders treatment center.

Udonella myliobati n. comb. (Platyhelminthes:Udonellidae) and its occurrence in eastern Australia.

A total of 2,571 of the copepod Caligus epidemicus Hewitt from the yellow-fin bream, Acanthopagrus australis Günther, was examined for udonellids. Calinella myliobati Guberlet, 1936 was found on 3.3% of male copepods and 10.1% of female copepods. A new combination, Udonella myliobati (Guberlet, 1936) is proposed and its description emended. It differs from the type species Udonella caligorum Johnston, 1835 (as described by Price [1938]) in having a short egg filament and a median genital aperture. Only 1 of 102 chalimus larvae was infected, by a single adult worm. Juvenile udonellids common on mature copepods, were not found on any of the chalimus larvae. The highest number of U. myliobati (Guberlet, 1936), including hatching and unhatched eggs on 1 copepod, was 159. Adult and juvenile worms were attached mainly along the margins of the carapace and to the genital complex, whereas the majority of the eggs were attached to the ventral surface of the genital complex. The transfer of an adult worm from a male copepod to a female copepod was observed while the copepods were copulating. The large number of udonellids on a small population of mostly female copepods from the Brisbane River suggested that this was an aging population of copepods compared to the copepods collected from a semi-enclosed pond.

Variation in the development of two isolates of Cryptocaryon irritans.

Two isolates of Cryptocaryon irritans obtained from Acanthopagrus australis from Moreton Bay (isolate C1) and Gymnocranius audleyi from Heron Island (isolate C2) were passaged on Lates calcarifer and Macquaria novemaculeata at 20 and 25 C under identical laboratory conditions. There were significant differences between isolates in the diameter of trophonts and tomonts, the incubation period of tomonts, and the length of theronts. Trophonts of C1 were significantly larger on L. calcarifer than on M. novemaculeata and showed marked size variation with temperature, whereas trophonts of C2 developed equally well on both species and showed little size variation with temperature. Tomonts of C1 were significantly larger than those of C2 when grown on L. calcarifer, whereas on M. novemaculeata tomonts from C1 were significantly smaller than C2 tomonts. The incubation period of tomonts from C1 was significantly shorter than that for tomonts of C2, and theronts of C1 were significantly larger than theronts of C2 under all host/temperature conditions. The differences in the development of these isolates are of biological and epidemiological importance. This indicates that distinct intraspecific variants of C. irritans occur along the coast of southeast Queensland.

Influence of temperature and host species on the development of Cryptocaryon irritans.

The course of infection of the parasitic ciliate Cryptocaryon irritans was followed on Lates calcarifer and Macquaria novemaculeata at 20 and 25 C. The parasite was originally isolated from locally caught Acanthopagrus australis. At 20 C trophonts stayed on the fish longer, tomonts took longer to excyst, and the resulting theronts were larger than at 25 C. On L. calcarifer at 20 C, trophonts grew slowly at first but eventually became significantly larger (mean tomont diameter 466 x 400 microns) than at 25 C (mean diameter 373 x 320 microns). On M. novemaculeata, trophonts never grew as large as on L. calcarifer and at 20 C they grew poorly. The number of theronts produced per tomont was directly related to the size of the tomont but was not influenced by incubation temperature. The tomont incubation period was not related to the diameter of the tomont but was significantly influenced by the host origin of the tomont. Theront size was also significantly affected by the host origin of the tomont but not the diameter of the tomont. These results show that C. irritans exhibits variability in morphometrics on different hosts and under different temperature conditions. This variability needs to be taken into account if utilizing morphometric data for separating strains of C. irritans.

Dynamics of the interaction between the parasitic isopod, Anilocra pomacentri, and the coral reef fish, Chromis nitida.

Field and laboratory investigations into the effect of the parasitic isopod Anilocra pomacentri (Cymothoidae) on the population dynamics of the reef fish Chromis nitida (Pomacentridae) were carried out at Heron Island, Great Barrier Reef, Australia. Fish carried a single adult parasite just posterior and dorsal to the eye either to the right or to the left of the midline. The adult parasite was overdispersed among fish on patch reefs (dispersion factor, k = 0.69). Sequential field observations on a single cohort of fish showed that parasites significantly depressed growth, reproduction, and survivorship. The von Bertalanffy growth coefficients (a measure of somatic growth) were 0.10 for parasitized fish compared with 0.17 for non-parasitized fish. Female fish carrying the parasite produced only 12% of the number of eggs produced by non-parasitized fish of the same size. In the field, the mortality of infected juvenile C. nitida (LCF 15-30 mm) was estimated to be at least 88% in the first 70 days after recruitment of the fish. The mortality of uninfected recruits over the same period was 66%. In laboratory trials, the mortality associated with the infection of juvenile fish by larval parasites ranged from 78% for small fish (mean LCF 15.0 mm) to 28% for larger fish (mean LCF 24.9 mm) within 4 days of experimental infection. This is one of the few studies that evaluates the effect of a parasite on a population of fish in the field.

The influence of formalin, benzocaine and hyposalinity on the fecundity and viability of Polylabroides multispinosus (Monogenea: Microcotylidae) parasitic on the gills of Acanthopagrus australis (Pisces: Sparidae).

Adult Polylabroides multispinosus exposed in vivo to formalin (200 p.p.m. in sea water, 30 min) deposited a similar number of eggs in 24 h in vitro as did control parasites (sea water, 35 parts per thousand, p.p.t., salinity) and worms exposed in vivo to benzocaine (40 p.p.m. in sea water, 10 min). Worms laid more eggs at 30 p.p.t. salinity in vitro than at 20, 35, 10 and 5 p.p.t. salinity (in decreasing order). Formalin (200 p.p.m., 30 min) decreased the viability of recently laid eggs, the survival of oncomiracidia, removed 70% of juvenile and adult worms from the gills, but decreased only slightly the viability of eggs exposed in utero or after eyespots developed in vitro. Salinities below 30 p.p.t. reduced viability as did an increase in temperature from 24 to 28 degrees C. All adult and juvenile worms were removed by baths in formalin (400 p.p.m., 25 min) or fresh water (1 h).