Nine species of parasitic copepods are reported, with 3 of them being new to science. They are: (1) Chondracanthodes deflexus Wilson from Antimora rostrata Günther, Coryphaenoides (Chalinura) brevibarbis (Goode and Bean), Coryphaenoides (Nematonurus) armatus (Hector), Coryphaenoides (Chalinura) leptolepis (Günther), and Coryphaenoides (Lionurus) carapinus (Goode and Bean); (2) Chondracanthodes radiatus (Müller) from Macrourus berglax Lacepede; (3) Lernaeopodina pectinata sp.nov. from Alepocephalus agassizi (Goode and Bean); (4) Neobrachiella pinguis (Wilson) from Antimora rostrata Günther; (5) Clavella adunca (Strøm) from Macrourus berglax Lacepede; (6) Sphyrion lumpi (Krøyer) from Antimora rostrata Günther; (7) Lophoura gracilis Wilson from Synaphobranchus kaupii Johnson; (8) Lophoura pentaloba sp.nov. from Coryphaenoides (Nematonurus) armatus (Hector) and Nezumia bairdii (Goode and Bean) and (9) Lophoura tetraphylla sp.nov. from Antimora rostrata Günther. The infected fishes were collected with trawls from depths of 828 to 4815 m in the New York Bight and 403 to 1294 m near the Grand Banks (south of Newfoundland).

The morphology of the adult blood fluke Schistosoma edwardiense sp.nov. from Hippopotamus amphibius L. is described and compared with that of other species of Schistosoma.

I wish to acknowledge the receipt of a research grant from Makerere University College towards expenses incurred during this work. I should like to thank Captain F. Poppleton, Warden of the Queen Elizabeth National Park, Dr R. M. Laws, Nuffield Unit for Tropical Animal Ecology, and Dr W. M. Longhurst, University of California, for helping me to get specimens from the hippopotami, also Mr L. Rugema, histologist, for sectioning the worms.

Neonatal hamsters were exposed to varying doses of Necator americanus larvae and changes in the stability of the resulting worm burdens were monitored over a period of 25 weeks. No change in worm burdens was evident for the first 5 weeks of infection, irrespective of the infection intensity, but the more heavily infected groups subsequently lost worms in a density-dependent manner. Male and female hamsters lost comparable proportions of their established parasite burdens indicating that there was no host sex-linked difference in this respect. By week 15 infections had stabilized and the residual worm burdens, usually a maximum of 30 worms survived for a considerably longer period of time. Initially the percentage of male worms varied from 45% to 50% but as infection progressed male worms comprised a significantly increasing proportion of the total worm burden. By week 25 the percentage of male worms was usually in excess of 60%. The growth of infected animals was not severely affected by N. americanus, even when heavy worm burdens established initially, but a significant effect was detected particularly in week 5, prior to worm loss, when the adult worms would have been feeding on intestinal tissues and causing blood loss for a period of about 2 weeks. The most severe depression in the packed cell volume was also recorded in week 5, indicating that anaemia had been initiated in infected hamsters. Whilst, the regulation of parasite burdens in weeks 5–10 post-infection may have resulted from host immunity, the persistence of the residual worm burdens, the marked density-dependent anaemia and the subtle effect on host weight, all reflected well-documented aspects of chronic human necatoriasis.

A simple apparatus for the collection of helminth eggs from faeces by means of a gas-circulated saturated salt solution is described. Nearly all the Nematodirus spp. eggs in both bovine and ovine faeces were recovered and shown to be viable.

The material described in the present paper was collected by Dr Rašín in 1935. It consisted of an infected ovary of Leuciscus cephalus L. from the Svitava river near Brno, and an ovary of Esox lucius from Ríčka in the vicinity of Vranovice near Brno, C.S.R. The ovaries were fixed partly with formol-Zenker solution, and partly with Gilson's fixative. The infected roes could be distinguished easily from the healthy ones by their white colour. Histological examination showed that they were infected with Microsporidia. As the material had been fixed, no polar filaments could be observed. Sections, 4μ in thickness, were stained with Heidenhain's iron haematoxylin, which once more proved to be a stain which gave the greatest contrast in preparations of Microsporidia. In addition, sections were stained with Mallory and Mann's stains, and were also subjected to Feulgen's nucleal reaction.

Elsewhere (paper in the Press) the author has shown that the majority of species originally described under Goniodes, although somewhat diverse in form, are fundamentally similar and cannot be separated generically. However, there are certain species originally placed in Goniodes which are generically distinct and should be separated. Among these is a group of species, forming the new genus described below, which is distinguished in both sexes by the small size of the first segment and the characters of the terminal segments of the abdomen and in the male by the form of the clavi.

1. The percentage conversion of cercariae into schistosomula, when the former were penetrating human epidermal sheets, was found not to be significantly affected by the underlying media 1—5 (Table 1). The percentage conversion varied from 16·4% (in normal saline underlying skin) to 26.2 %. When distilled water was the underlying medium significantly fewer cercariae penetrated the sheets.

2. There was a statistically significant decrease in the percentage conversion of cercariae to schistosomula when sodium chloride final concentration 0·67 % was placed in the exposure tube with the cercariae (1·6 % P = < 0·02 when compared with La Ye medium); 0·43 % sodium chloride also significantly decreased penetration.

3. There was a statistically significant decrease in the percentage conversion of cercariae to schistosomula when the orientation of the human epidermis was reversed, i.e. the biologically inner surface was exposed to the cercariae (2.6 %, P = < 0.02, when compared with La Ye medium).

4. Schistosomula agglutinated in the presence of normal or immune human serum or horse serum. In human serum to which donor red blood cells had been added, many red cells adhered to the schistosomula. The number adhering was less in inactivated serum. The adhesion was specific for red cells, the effect not occurring with either yeast cells or silicic acid particles. The red cells were shed from the surface of the schistosomulum after 4—12 h.

I should like to thank the following: Dr S. A. Ibrahim, in whose laboratory this work was carried out; Dr S. Dawood of the Stack Laboratory, Khartoum for the use of his microscope; Mr T. R. Melrose and Mr J. R. Lauder for valuable discussions; the Medical Research Council, U.K., and the University of Khartoum for research grants. I am very grateful to the Pathology Department Faculty of Medicine, University of Khartoum, for preparing the sections of human epidermis.

We have cloned a cDNA encoding a novel antigen from a Sarcoptes scabiei (Acari) cDNA library by immunoscreening with sera from S. scabiei-infected dogs. The antigen is encoded by a 2157 bp mRNA with a predicted open reading frame of 719 amino acids (molecular weight 79 kDa). Our sequence analysis identified the presence of a MADF domain in the N-terminus, and downstream of this domain there was a region of low sequence complexity. This latter region contained several blocks of triplets and quadruplets of polar amino acids (Asn, Gln and Ser), and these 3 amino acids represented 39·7% of all amino acids. The antigen was named Atypical Sarcoptes Antigen 1 (ASA1) since the MADF domain normally is found in proteins involved in transcriptional regulation. In addition, 15 out of 62 S. scabiei-infected dogs reacted with a purified recombinant version of ASA1 in Western blot analysis. With immunohistochemistry we could show that ASA1 is expressed throughout the parasite, and that IgG specific for ASA1 binds to the inside wall of the mite's burrow. To our knowledge, this is the first description of an antigen containing an MADF domain.

Rhabditiform first-stage larvae of Nippostrongylus muris are about 270–550μ long. The development of these larvae culminates in a moult, which occurred 36–48 hours after cultures were prepared. The first moult is preceded by an unusually early separation of the first cuticle, which is fine and unstriated, from the body tissue in the tail region and, later, by the formation of an underlying new cuticle, which is thicker and prominently striated.

Early second-stage rhabditiform larvae differ in certain morphological respects from first-stage larvae. Second-stage larvae are about 470–750μ long.

A second preparasitic ecdysis occurs and the infective larva is a true third-stage larva. This moult was the only one previously known to occur during the preparasitic development of N. muris.

The post-cervical cuticular inflation in N. muris is regarded, on the basis of a comparative study of the cuticle of this species and of Haemonchus contortus and other trichostrongyles, as resulting from the separation of the second and third layers of the cuticle. Yokogawa's view that Nippostrongylus muris has two cuticulae is rejected. N. muris has a single cuticula, apparently made up of four layers.

N. muris undergoes four complete moults and the development of this species does not differ in any essential respect from that reported for other strongyles.

Anthobothrium auriculatum (Rud.) is often referred to as ‘an insufficiently known species’. Southwell (1925) states that ‘all that is known about this doubtful species is contained in Rudolphi's brief description, which is quite insufficient to diagnose the species with, certainty’. Rudolphi (1819) first described it as Bothriocephalus auriculatus from Torpedo marmorata Risso; it is possible that this brief and inadequate description included several species. Leuckart (1820) described what has since been regarded as the same species under the name of Bothriocephalus flos from Carcharinus glaucus (L.), Bremser (1824) gave a brief account of Bothriocephalus auriculatus, and Zschokke (1888) gave a somewhat fuller account of Anthobothrium Auriculatum from Torpedo marmorata. As far as can be judged all these forms are synonymous. Diesing (1850) described what he thought to be Rudolphi's species, placing it in the genus Tetrabothrium; he obtained it from Torpedo marmorata Risso, Hexanchus griseus (Gm.), Carcharinus glaucus (L.), Squatina squatina (L.), and Raja calvata L. It has been pointed out by several writers that Diesing's Tetrabothrium auriculatum does not agree with Anthobothrium Auriculatum (Rud.), because, among other things, the genital pores in the former are anterior and in the latter posterior. Southwell (1925) states that Beauchamp is of the opinion that Tetrabothrium auriculatum Dies, is synonymous with Phyllobothrium gracile Wedl., an idea which is now generally accepted. Joyeux & Baer (1936) recorded Anthobothrium Auriculatum (Rud.) fairly frequently in a number of host fishes, namely, Mustelus mustelus (L.), Scyliorhinus caniculus (L.), Lamna cornubica (Gm.), Eugaleus galeus (L.), Squatina squatina (L.), Carcharias glaucus (L.), Torpedo marmorata Risso, and Raja clavata L. They, too, refer to the species as imperfectly known, and suggest that it might be synonymous with some other species of the same genus. In view of the lack of an adequate description of Anthobothrium Auriculatum it was felt that an account of its anatomy would render future identification of the species simpler and would settle the question as to whether or not it was synonymous with some other known species.

Plasma membrane vesicles prepared from the bag region of the somatic muscle cells of the parasitic nematode Ascaris suum contain high conductance, voltage sensitive, Ca-dependent chloride channels, suggested to be involved in the excretion of carboxylic acids produced by the anaerobic respiration of glucose (Valkanov, Martin & Dixon, 1994). The effect of altered pH on this channel was investigated using the patch-clamp technique and isolated inside-out membrane patches. Changes in pH had little effect on channel conductances and only a small effect on reversal potentials. Under control conditions (symmetrical pH 7·2) the channel had the highest probability of opening at ∼ — 35 mV (the resting membrane potential of the cell). At positive membrane potentials the probability of opening decreased. The Boltzmann equation was used to describe the relationship between membrane potential and probability of channel opening, and to calculate the effective gating charge. Reduction of external pH produced an increase in the probability of channel opening at hyper-polarized membrane potentials. An increase in internal pH caused a voltage-independent increase in the probability of channel opening and made the effective gating charge less negative. The effect of reducing internal pH was marked: the channel then opened most frequently at positive membrane potentials and the probability of opening at —35 mV was greatly reduced. The decrease in internal pH changed the polarity of the effective gating charge. A simple model was constructed to describe the effects of pH on channel gating.

A description is given of a new species of Henneguya (Myxosporidia), named H. tegidiensis sp.nov. It is parasitic in the freshwater fish, Coregonus clupeoides pennantii, from Lake Bala (North Wales), producing in it intramuscular cysts.

Neobenedenia girellae, a capsalid monogenean, is a significant pathogen due to both its ability to cause high mortality in fishes and its low host specificity. Established control methods have both advantages and disadvantages. Biological control measures with no unfavourable effects on the environment should be incorporated into the control strategy. The response of N. girellae oncomiracidia to brightness and black-and-white contrast was investigated to search for an alternative approach of disease prevention or control. Japanese flounder, Paralichthys olivaceus (Paralichthyidae), were exposed to oncomiracidia in an aquarium divided into areas of different brightness (∼1·3, 41·3 and 138·0 lux). The number of parasites on the fish group reared in 138·0 lux was significantly higher than on those reared in the lower brightness levels. Thus, the fish tended to be more vulnerable to infection by N. girellae under brighter conditions. Challenge trials using host fish mucus and whole live fish were established to detect the response by oncomiracidia to black-and-white contrast on a white versus a black background. Markedly more N. girellae oncomiracidia attached to black-painted areas and dark-coloured fish (normal spotted halibut, Verasper variegatus (Pleuronectidae) compared with white-painted areas and light-coloured fish (mal-coloured V. variegatus) on a white-coloured background. On a black-coloured background, more N. girellae oncomiracidia tended to attach to white-painted areas and light-coloured fish. Thus, black-and-white contrast is considered important for host finding by N. girellae oncomiracidia. The simplicity of the positive phototactic behaviour and the response to black-and-white contrast may lead to the development of a simple, practical and inexpensive method to control N. girellae outbreaks.

In August 1948 a student from this department, Mr J. N. Upton, went on a commercial trawler to the fishing grounds off the coast of Iceland and brought back a collection of parasitic worms from some of the fishes caught in the trawl. Being unable to continue the investigation Mr Upton handed the specimens to the writer for identification and further study. The writer is most grateful for the gift of this collection.

The eggs and oncomiracidia of two species of the capsalid genus Encotyllabe are described. These parasites were identified tentatively as E. caballeroi Velasquez, 1977 and E. caranxi Lebedev, 1967. If these identifications are correct, then E. caballeroi is recorded from two new hosts, Gymnocranius audleyi and the nemipterid Scolopsis monogramma, and E. caranxi from a new host, Pseudocaranx dentex, and a new locality, Heron Island, Queensland, Australia. Encotyllabines have not previously been recorded from fishes of the family Nemipteridae. The eggs of the two parasites failed to hatch spontaneously and did not hatch when exposed to a variety of potential hatching stimuli, but the oncomiracidia within survived for many weeks. Oncomiracidia expelled from eggs by cover-slip pressure are unciliated and possess a saucer-shaped haptor like that of other capsalids with three pairs of median sclerites and 14 marginal hooklets. The paths of tendons associated with the accessory sclerites and the presence of haptoral loculi suggest that encotyllabines are related to the trochopodines. Observations on a single juvenile specimen of E. caballeroi show that the accessory sclerites and the tendons are lost early in development and that one pair of hamuli (probably the posterior pair) ceases to grow early in post-oncomiracidial life. The loculi persist a little longer but also disappear before full sexual maturity is reached.

The North American opossum, Didelphis virginiana, is a definitive host for at least 3 species of Sarcocystis:S. falcatula Stiles 1983, S. neurona Dubey, Davis, Speer, Bowman, de Lahunta, Granstrom, Topper, Hamir, Cummings, Suter 1991, and S. speeri Dubey and Lindsay 1999. In order to identify species of Sarcocystis in the South American opossum, D. marsupialis, Sarcocystis sporocysts from the intestines of a naturally infected opossum (D. marsupialis) from Brazil were fed to 4 gamma-interferon knockout (KO) mice, a nude mouse, and 2 budgerigars (Melopsittacus undulatus). All 4 KO mice became ill and 1 died 42 days post-feeding (p.f.) of sporocysts, 1 was killed 44 days p.f. because of neurological signs, and 2 were killed 52 and 53 days p.f. because of abnormal gaits. Numerous sarcocysts were seen in the skeletal muscles of all 4 KO mice and they were structurally identical to S. speeri seen in KO mice fed sporocysts from D. virginiana from the United States and D. albiventris from Argentina. The nude mouse was killed 41 days p.f. because it appeared weak; schizonts were seen in sections of its liver and sarcocysts were seen in sections of skeletal muscles. Sarcocystis speeri was cultured in bovine turbinate cells inoculated with liver homogenate from this mouse. Sarcocystis neurona was not demonstrable in tissues of mice. The two budgerigars remained asymptomatic and S. falcatula was not found in their tissues when they were killed 29 days p.i. This is the first report of S. speeri from D. marsupialis.

Observations out of doors demonstrated that the viability of embryonated eggs in soil was adversely affected by dryness. This was confirmed in laboratory experiments.

The resistance of embryonated eggs to temperatures below freezing-point was observed both out of doors and in the laboratory.

The rate of development of larvae in the intermediate host was reduced as the temperature fell.

The longevity of the infective larvae appeared to be largely determined by the longevity of the earthworm intermediate host, although they were able to survive for a time when separated from the earthworm's tissues.

The longevity of eggs and larvae under natural conditions and the persistence of infection on a pasture are discussed.

Trypanosoma cruzi epimastigote reservosomes store nutrients taken up during the intense endocytic activity exhibited by this developmental form. Reservosomes were classified as pre-lysosomal compartments. In contrast, trypomastigote forms are not able to take up nutrients from the medium. Interestingly, trypomastigotes also have acidic organelles with the same proteases contained in epimastigote reservosomes. Nevertheless, the origin and function of these organelles have not been disclosed so far. Given the similarities between the compartments of epimastigotes and trypomastigotes, the present study aimed to investigate the origin of metacyclic trypomastigote protease-containing organelles by tracking fluorospheres or colloidal gold particles previously stored in epimastigotes’ reservosomes throughout metacyclogenesis. Using three-dimensional reconstruction of serial electron microscopy images, it was possible to find trypomastigote compartments containing the tracer. Our observations demonstrate that the protease-containing compartments from metacyclic trypomastigotes may originate directly from the reservosomes of epimastigotes.

There are few, if any, authenticated records of fossil helminths or even of the hard parts of ectoparasitic monogeneans. This means that theories of helminth evolution can be based only on indirect evidence and are unlikely to be confirmed or refuted by palaeontologists.

Currently three main areas of study provide evidence of evolutionary trends: (i) morphology, in its broadest sense; (ii) life-history studies; (iii) host spectra and geographical distribution.

Data on 279 species of trematodes of birds and mammals are analysed in tables, to show the molluscan orders and families that act as first intermediate hosts of various trematode families.

Host-specificity is highly developed in the first larvae of trematodes and it is suggested that, as a consequence of this, certain species, genera and families of molluscs harbour a greater variety of trematodes than others. The families Lymnaeidae, Physidae, Planorbidae, Hydrobiidae and Thiaridae are by far the most important first-intermediate hosts of the trematodes of birds and mammals whose life cycles are known; each family acting as host of not less than twenty-four species and eight families of trematodes.

This paper is published with the approval of the Director General of Health, Canberra, A.C.T.