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.

The cypris larvae of the parasitic barnacle Heterosaccus lunatus (Crustacea, Cirripedia, Rhizocephala): some laboratory observations

Heterosaccus lunatus parasitizes the portunid crab, Charybdis callianassa in Moreton Bay, Australia. With the host crabs maintained at 22.5 degrees C this sacculinid rhizocephalan released larval broods every 6-7 days. During July-August 1996 and particularly August 1999 such broods showed the change-over from male only larvae in the early broods to females only in the later broods. As the host crabs were maintained under similar aquarium conditions in both years it is concluded that the light/dark cycle is the principal cue triggering this larval sex reversal. Oogenesis in the parasite externa is somehow controlled to produce two different sized ova - male larvae develop from large ova and females from small ova. A working hypothesis outlining how sex is probably determined for the larvae of sacculinids is erected. H. lunatus is considered the ideal sacculinid for the further experimental work necessary to verify the proposed sex-determining mechanism and its control processes. Measurements of the maximum swimming speeds of H. lunatus male and female cyprids showed the larger males to be the faster in absolute terms (27.95 compared with 17.60 mm s(-1), respectively), however, the calculated relative speeds were almost identical at approximately 90 body lengths s(-1). Settlement experiments confirmed that female H. lunatus cyprids settle only on the gills of C. callianassa; these cyprids needed to be at least 2 days old before they were able to settle.

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.

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.

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).

Epizootic mortality of free-living green turtles, Chelonia mydas, due to coccidiosis

At least 70 wild green sea turtles, Chelonia mydas, died in the Moreton Bay area of southeast Queensland, Australia over 6 wk in spring 1991. Based on the necropsy of 24 turtles, there was a severe enteritis or encephalitis associated with Caryospora cheloniae, a coccidial pathogen previously recorded only in farm-reared Ch. mydas hatchlings. Infection was characterized by the presence of coccidia in extra-intestinal lesions. Oocysts were observed to sporulate, after which sporozoites escaped into seawater to form a novel stellate configuration. We conclude that C. cheloniae is pathogenic for life stages other than hatchling Ch. mydas and that naturally-occurring coccidiosis is a significant disease of free-living Ch. mydas.

Sporulation of Marteilioides branchialis n. sp. (Paramyxea) in the Sydney rock oyster, Saccostrea commercialis: an electron microscope study

The ultrastructure of sporulation of a new parasite, Marteilioides branchialis (Paramyxea), in the Sydney Rock oyster, Saccostrea commercialis, is described. The development is typical of other Paramyxea whereby a stem cell internally cleaves a secondary cell contained within a vacuole. It differs from other species in the phylum in that each secondary cell produces a single spore composed of two concentric cells, one within a vacuole of the other. This type of sporulation represents the simplest of all known Paramyxea. Infection results in focal gill lesions and was observed concurrently with an epizootic of another paramyxean, Marteilia sydneyi.

Closed loop control of vasoactive drug infusion. A preliminary report

A closed loop control system for vasoactive drug infusion is described using a dedicated bedside microcomputer and a single volumetric infusion pump. The signal from an indwelling arterial cannula is taken from the bedside monitor through an analogue/digital converter to a microcomputer. After signal validation changes of infusion rate are calculated and communicated to a volumetric infusion pump through an RS 232 interface. The system has been successfully employed in four patients during cardiac surgery prior to cardiopulmonary bypass and in six cardiac surgical patients in the postoperative period. In both groups mean arterial pressure was controlled within 5 mmHg of target value for 75% of infusion time, and within 10 mmHg for 90% of the duration of infusion.

An estimate of the mortality in a population of Perca flavescens owing to the trematode Diplostomum adamsi

A truncated form of the negative binomial distribution was fitted to the frequency distribution of 5117 metacercariae of Diplostomum adamsi in 115 Perca flavescens taken from the Bay of Quinte, Lake Ontario. Comparison between the fitted curve and the actual distribution suggested that 78 heavily infected fish were missing from the sample. Field and laboratory data indicated that this was due to a higher mortality in the heavily infected fish, particularly during their first 2 years of life, rather than to inadequate sampling, host resistance, or parasite–parasite interaction.

Diplostomum adamsi sp.n.: description, life cycle, and pathogenesis in the retina of Perca flavescens

Forty-two perch eyes (Perca flavescens) infected with metacercariae of Diplostomum adamsi were fed to a herring gull (Larus argentatus). Eighty adults were recovered from the intestine 10 days later. They were characterized by their small size (1.5 to 2.1 mm), asymmetrical anterior testis, and the absence of vitellaria in forebody anterior to the middle of the ventral sucker.Eggs of D. adamsi passed by the gull embryonated in 22 days at 22 °C and hatched when exposed to light. Miracidia penetrated snails of the species Lymnaea elodes and L. stagnalis. Forty days later straight-tailed cercariae with six pairs of caudal bodies were released from both lymnaeids. They penetrated and developed in P. flavescens but not in Salvelinus namaycush, Catostomus commersoni, Semotilus atromaculatus, or Carassius auratus. In P. flavescens, metacercariae were found in clusters in the peripheral retina, in a cavity between the photoreceptor cells and the pigment epithelium. The photoreceptor cells were disorganized but not destroyed, unlike those in the eyes of Gasterosteus aculeatus parasitized by D. scudderi.

Survival of two trematode parasites (Diplostomum spp.) in mammalian eyes and associated pathology

Cercariae of Diplostomum spathaceum dropped onto the eyes of small unanaesthetized rabbits penetrated through the cornea, crossed the anterior chamber, and entered the lens. After 2-3 weeks they died and became semi-permanent amorphous cataracts. Cercariae remaining in the cornea became the centres of stromal nebulae 0.1-0.2 mm across which remained visible for at least 3 months. Re-exposure produced marked conjunctival inflammation. Parasites applied to the eyes of large adult rabbits or cold-stored enucleated eyes of man entered the cornea but failed to penetrate as far as the anterior chamber. It is suggested that cercariae are unlikely to reach the lens of bathers because of the thickness of the human cornea. However, exposure to infection may result in temporary conjunctival inflammation and more persistant stromal nebulae. Cercariae of the closely related D. adamsi, did not penetrate or develop in the eyes of mammals.

Ultrastructural observations on the granulocytic leucocytes of the teleost Catostomus commersoni

Leucocytes from the blood and inflammatory tissues of C. commersoni were examined with the electron microscope. Neutrophils in sections of blood were recognized by their lobed nucleus and numerous irregularly shaped granules approximately 0.5 μm in diameter. Many of the granules had electron-dense inclusions. Eosinophils were characterized by a compact eccentric nucleus and oval, uniformly electron-dense granules measuring 0.8 μm in diameter. Cells tentatively classed as basophils had a lobed nucleus and spherical, uniformly electron-dense granules about 0.75 μm in diameter.Inflammatory tissue produced within 24 h of making a small incision contained numerous neutrophils and eosinophils. Many of the eosinophils were "degranulating." Their granules were enlarged and contained both electron-dense and electron-lucid areas. Some granules had apparently coalesced and others, presumably at a later stage in degranulation, had lost the granule membrane. Intact cells filled with granule-derived material were observed.

Gyrodactylus alexanderi: reproduction, mortality, and effect on its host Gasterosteus aculeatus

Individual flukes of the monogenetic trematode Gyrodactylus alexanderi, maintained at 15 °C on isolated fish (Gasterosteus aculeatus leiurus), gave birth to only two daughters, the first after an average of 1.6 days, and the second after 6.9 days. For at least 20 generations, the first daughter was produced every 1.6 days without cross-fertilization occurring. Maximum longevity at 15 °C was 28 days, but reached 71 days at 7 °C.The mean life expectancy of flukes away from fish was 1.8 days at 15 °C. This was shortened in the presence of young sticklebacks which preyed on the Gyrodactylus. One to 13% of flukes survived slow changes in salinity.Fish heavily infested with G. alexanderi died. Of 67 fish, 25–35 mm in length and carrying over 150 flukes. 54 died, compared with only 33 of 174 fish carrying fewer flukes. Deaths were not associated with infections of protozoa, fungi, or bacteria.

The influence of Schistocephalus plerocercoids on the respiration of Gasterosteus and a possible resulting effect on the behavior of the fish

Undisturbed infected fish consumed more oxygen than would uninfected controls of the same weight of fish tissue, the difference presumably being due to the parasite. When the fish were swimming, the extra consumption rose rapidly with an increase in speed, particularly in heavily infected fish. This increased oxygen requirement may account for the spatial distribution of infected fish suggested by field data.