The enemy release hypothesis proposes that in parasite depleted habitats, populations will experience relaxed selection and become more susceptible (or less tolerant) to pathogenic infections. Here, we focus on a population of guppies (Poecilia reticulata) that are found in an extreme environment (the Pitch Lake, Trinidad) and examine whether this habitat represents a refuge from parasites. We investigated the efficacy of pitch in preventing microbial infections in Pitch Lake guppies, by exposing them to dechlorinated water, and reducing gyrodactylid infections on non-Pitch Lake guppies by transferring them to Pitch Lake water. We show that (i) natural prevalence of ectoparasites in the Pitch Lake is low compared to reference populations, (ii) Pitch Lake guppies transferred into aquarium water develop microbial infections, and (iii) experimentally infected guppies are cured of their gyrodactylid infections both by natural Pitch Lake water and by dechlorinated water containing solid pitch. These results indicate a role for Pitch Lake water in the defence of guppies from their parasites and suggest that Pitch Lake guppies might have undergone enemy release in this extreme environment. The Pitch Lake provides an ideal ecosystem for studies on immune gene evolution in the absence of parasites and long-term evolutionary implications of hydrocarbon pollution for vertebrates.

Sphaeridiotrema pseudoglobulus is a digenean parasite believed to be involved in a yearly fall die-off of ducks in Québec, Canada. Hatching characteristics of eggs stored at 7°C for 0–28 weeks in the lab and following maintenance overwinter in a lake are described. The hatching success of eggs stored for 4–28 weeks remained constant (71–81 %) but slightly less than that observed in fresh eggs (90%). The hatching success of eggs kept overwinter under natural conditions did not differ from that of eggs stored an equivalent length of time in the lab at 7°C (74·7 and 75·8%, respectively). With the exception of fresh eggs (17·7 days), the mean hatch time of eggs steadily decreased with increased storage time (18·9 days following 4 weeks storage to 11·4 days at 28 weeks storage) due to a slow embryonation of the eggs at 7°C. Hatching characteristics of a subsample of eggs incubated at 10, 15 and 20°C were compared and the embryonation rate was found to increase with incubation temperature. The majority of eggs stored at 10°C embryonated but failed to hatch. When their incubation temperature was raised to 15°C, a further 46% hatched within the following week. The survivorship functions of miracidia hatching from eggs stored for 8, 12, 16 and 20 weeks differed but the mean expected life-span of the miracidia did not decline with increasing storage time as expected. The results of these experiments are discussed in relation to the potential importance of overwintered eggs in the development of the infective pool of metacercariae.

This paper demonstrates the use of a quantitative genetical technique to assess genetic variance in molluscicide resistance in a Millettia thonningii-Biomphalaria glabrata system. Results indicated that there were significant genetic variances in both snail size and survival time in 10 p.p.m. molluscicide suspension. The possibility of wider applications of this technique in examining the genetic basis of molluscicide or pesticide resistance in target species is discussed.

The cuticle of parasitic nematodes, the main contact site with the host, plays an important role in host-parasite interaction and thus also in immunological control. We compared different surface-iodinated life-stages of the filarial worm Dipetalonema viteae (microfilariae, infective 3rd-stage larvae (L3), adult males and females) with respect to changes in their surface composition. Autoradiographs of peptide maps show that all stages present an identical set of peptide spots reflecting common surface protein(s). Spots specific for larvae L3 show that the composition of the iodinated surface differs in microfilariae and adults i.e. it changes during development. Adults show a spot typical for males or females. Identical spots are found in L3. This suggests that a surface component is also sex specific.

Clinical trichostrongylosis, caused by T. tenuis in the caeca, previously known in epizootic form among gallinaceous birds in Great Britain, is here reported for the first time in this country, in native domestic geese in the District of Columbia and in imported pheasants in Michigan.

In cultures made from caecal contents of infected pheasants, eggs hatched in 36–38 hours; the infective larval stage might be reached as early as the sixth day (fourth day after hatching). Moisture being present, migrating larvae, retracted within the cuticular sheath, resisted an average temperature of about −3° C. (range +3° to −20° C.) for 4 months, proving infective for a bird host at the end of that period. The chicken, turkey and guinea-fowl were successfully infected with cultures derived from pheasants; attempts to infect the duck and pigeon with cultures from pheasants, and to infect the duck with cultures from geese, were unsuccessful. Development to adults in bird hosts took place in a minimum of 7 days after infection; the size of adults varied in different birds, being greater in the chicken than in the pheasant, and still greater in the turkey. In early stages of infection diarrhoea from the caeca, with passage of mucus and blood, occurred; later all discharge from the caeca ceased. The pathological picture was that of acute typhlitis, with the trichostrongyles lying in close contact with or penetrating the mucosa. Reinfection being prevented, symptoms were of fairly short duration, and the infestation tended to die out in about 2 months.

The following paper lists the species of cestodes, not hitherto described by the author, obtained from Burmese animals during the years 1923–5. Many of the specimens were collected by Miss I. K. Reynolds while working in the Zoological Department of University College: the writer wishes to acknowledge his indebtedness to her for the use of data, material and slides. He also wishes to express his thanks to the Trustees of the Victoria Memorial Park for permission to collect helminths from animals dying in the gardens.

Adult Ostertagia circumcincta from freshly killed sheep were incubated at 39 °C in a medium containing inorganic salts, antibiotics and D-[U-14C] glucose. The worms appeared healthy even after incubation for as long as 72 h. All the radioactivity was recovered either within the worms or in the incubation vessel in the form of metabolic products or unmetabolized glucose. Incubations were carried out at low oxygen tension except for those in which CO2 was measured. These were either aerobic or anaerobic. In terms of both quantity and radioactivity the main metabolic products of glucose were CO2, propan-1-ol, acetate and propionate. Smaller amounts of ethanol, lactate and succinate were formed. The results are compared with those found for the similar nematode Haemonchus contortus.

In this second contribution to the study of parasitic copepods of fish from Ceylon eight species are described, four of which are new. The male of one species, namely that of Euryphorus nordmanni Milne-Edwards, is described for the first time. Of the three remaining species, Caligodes laciniatus Kröyer has only been recorded once (Heller, 1865) since it was originally described in 1863 and the comparison of Caligus alalongae Kröyer and C. tenax Heller makes it easier to identify the males of these two forms.

PTPases have been reported as a virulence factor in different pathogens. Recent studies suggest that PTPases play a role in the pathogenesis of Leishmania infections through activation of macrophage PTPases by the parasite. We report here the presence of a membrane-bound PTPase in Leishmania major promastigotes. We detected differences in the PTPases present in the procyclic and metacyclic stages of promastigotes. In metacyclic promastigotes, the PTPase activity was totally inhibited by specific PTPase and serine/threonine inhibitors, whereas in procyclic promastigotes the PTPase activity was inhibited only with PTPase inhibitors. Two antibodies against the catalytic domains of the human placental PTPase1B and a PTPase from Trypanosoma brucei cross-reacted with a 55–60 kDa molecule present in the soluble detergent-extracted fraction of a Leishmania homogenate. Metacyclic promastigotes expressed more of this molecule than parasites in the procyclic stage. Yet the specific activity of the enzyme was lower in metacyclic than in procyclic promastigotes. Ultrastructural localization of the enzyme showed that it was more membrane-associated in metacyclic promastigotes, whereas in procyclic promastigotes it was scattered throughout the cytoplasm. This is the first demonstration of a PTPase present in Leishmania major promastigotes that differs in expression, activity and ultrastructural localization between the procyclic and metacyclic stages of the parasite's life-cycle.

Gametocytes of a polychromophilid parasite indistinguishable from those of P. melanipherus are commonly found in the blood of the bent-winged bat Miniopterus schreibersii in New South Wales. There is a seasonal variation in infection rate, this being lowest in April (0%) and highest in August (up to 82·7%), and in density of parasitaemia.

This variation is the reverse to that found in the same species of bat in the northern hemisphere.

The reproductive biology of M. schreibersii in New South Wales is considered in relation to the seasonal variation in infection rate.

The main vectors of the parasitism are likely to be the nycteribiid flies, Penicillidia oceanica and Nycteribia parilis n.ssp.

1. An account is given of the intensity and incidence of infestation of the scorpaenid redfish, Sebastes marinus and S. mentella, by the parasitic copepods Peniculus clavatus, Sphyrion lumpi and Chondracanthopsis nodosus on three fishing grounds in the eastern North Atlantic, namely Iceland, Bear Island and the Barents Sea.

2. Peniculus clavatus was found to be a rare parasite on both species of redfish in the eastern North Atlantic. Adult female parasites were found during the months from September to February only; they were usually attached to the pelvic or dorsal fins of the host causing little damage.

3. Sphyrion lumpi was found to be a comparatively rare parasite on the deep-water Sebastes mentella throughout the eastern North Atlantic but it was found on S. marinus in the vicinity of Bear Island only. It seems justifiable to regard the Bear Island grounds as a centre of abundance of Sphyrion lumpi in the eastern North Atlantic. Adult female S. lumpi tended to infest medium-sized redfish more often than smaller or larger fish.

4. The infestation of Sebastes marinus and S. mentella by Chondracanthopsis nodosus has been examined in some detail and attention directed to the influence on infestation of the host species, geographical distribution, body length, age and sex of the host, and seasonal variations. The distribution of female C. nodosus within the gill chamber of the two species of redfish is described; it appears to be related to the need of the parasite to secure a protected and spatially limited habitat out of the mainstream of the ventilation current through the gill chamber.

5. The ecological relationships between Sebastes marinus and S. mentella and the three species of parasitic copepod are described together with the possibility of using these and other parasites as indicators of the host's mode of life. It is concluded that Chondracanthopsis nodosus and Sphyrion lumpi merit more detailed and extensive study as possible parasitological indicators of different stocks of redfish.

I wish to express my thanks to Messrs Jackson Mills Ltd., Fish Merchants and Curers, Hull, and to the Officer-in-Charge, D.S.I.R., Humber Laboratory, Hull, for their generous assistance in making redfish available for examination. I am also most grateful to Miss E. C. Howard, Librarian, Ministry of Agriculture, Fisheries and Food, Fisheries Laboratory, Lowestoft, for her invaluable assistance in providing certain otherwise unobtainable references in the literature.

The distribution of Paragonimus kellicotti metacercariae in a mixed population of crayfish from a small central Ohio stream was studied for two seasons. The distribution of worms in crayfish approximates the negative binomial distribution. Prevalence and intensity of infection increased with crayfish body weight. Although no difference in intensity of infection was noted between male and female crayfish, the prevalence of infection was higher in males. The data demonstrate a seasonal recruitment of metacercariae into the crayfish only during late summer and autumn. Metacercariae can live for over 1 year but some die and become mineralized. There is no apparent detrimental effect of P. kellicotti infection on the crayfish. The seasonal timing of life-cycle events is postulated.

Cyclosporin A (CsA) induced significant changes in parasite morphology when administered to mice infected with Hymenolepis microstoma. Gross morphological damage consisted of proglottis swelling and the formation of protuberances from the worm surface, visible with a low-power dissecting microscope, occurring most frequently in the posterior third of the strobila. Gross morphology and ultrastructure were examined further using scanning and transmission electron microscopy. Swollen proglottides exhibited areas covered in small pits and fissures (diameter approximately 1–2 μm) but it was not possible to establish the significance of this damage. The brush-border and distal cytoplasm appeared largely intact although some evidence of swelling of the basal membrane invaginations and possible fluid accumulation was seen in drug-treated TEM sections. The apparent oedematous condition of many of the proglottides from drug-treated mice may indicate that CsA treatment mediates permeability changes in the worm surface membrane but the mechanisms by which this may occur remain to be elucidated. The effects of CsA on the morphology of H. microstoma correlate with the previously described anthelmintic activity of the drug against this parasite where CsA treatment dramatically reduces worm growth, retards migration into the bile duct and limits parasite survival.

This work contains the description of two new Coccidia parasitic in the South American lizard Cnemidophorus lemniscatus lemniscatus. One is identified as Eimeria flaviviridis americana subsp.nov., which is described and discussed in relation to the other species recorded from sauria. The other is Hoarella garnhami gen.nov., sp.nov., whose position in the family Eimeriidae necessitated a revision of the classification of the Coccidia Eimeriidae.

I wish to acknowledge the help and encouragement I received from Professor P. C. C. Garnham, in whose department this work was carried out. My thanks are also due to Dr Cecil Hoare for his private communications and assistance in the interpretation of histological specimens. The author is grateful for co-operation of the School's Photograph Staff and to members of the staff of the Department of Parasitology, especially to Mr P. E. Nesbitt for his valuable sections. Finally, the author is indebted to the Consejo de Desarrollo Cientifico y Humanístico de la Universidad Central, Caracas, for their assistance in the form of a scholarship during the tenure of which this work was produced.

As part of an integrated programme investigating human schistosomiasis, work which involves epidemiological surveys and detailed immunological studies as well as biochemical investigations, we have, over the last three years, been cloning schistosome genes in a variety of plasmid and lambda vector systems. In this lecture we present a review of some selected aspects of work primarily aimed at production of experimental vaccines against the disease but which, on a broader front, is also concerned with developmental regulation of gene expression around the parasite's life-cycle. Specifically, we are interested in cloning three groups of genes. First, those encoding surface antigens; second, those associated with sexual maturity and egg production; and third, antigens which may provide a basis for a specific immunodiagnostic test.

The aspidogastrid trematodes form a well-defined group of at most eight genera with a wide distribution. They are known from five continents and they occur in various cold-blooded hosts from both marine and fresh-water habitats, notably, Gasteropod and Lamellibranch molluscs, the larger Crustacea, some Fishes, and Chelonians. The recording of a new genus in a fresh locality is thus of some zoological importance.

Acquired resistance to paludrine in Plasmodium gallinaceum was retained undiminished after passage at frequent intervals through untreated chicks for more than 1 year.

The morphology of sexual adults is the cornerstone of digenean systematics. In addition, life cycle data have always been significant. The integration of these approaches, supplemented with molecular data, has allowed us to detect a new species that many researchers may have previously seen, but not recognized. Sexual adults from common eiders that we found in northern European seas were extremely similar to other notocotylids, but the discovery of their intermediate host, a marine snail, revealed the true nature of this material. Here we describe sexual adults, rediae and cercariae of Catatropis onobae sp. nov. We discuss how ‘Catatropis verrucosa’ should be regarded, justify designation of the new species C. onobae for our material and explain why it can be considered a cryptic species. The phylogenetic position of C. onobae within Notocotylidae, along with other evidence, highlights the challenges for the taxonomy of the family, for which two major genera appear to be polyphyletic and life cycle data likely undervalued.

Schistosomula of Schistosoma mansoni were incubated in RPMI 1640 medium containing 10% fetal calf serum, 10% human portal venous or 10% human peripheral venous sera in the presence of bromodeoxyuridine (BrdU) in order to measure differences in cell proliferation. The rates of cell proliferation as expressed by BrdU labelling indices (BLI) were determined as a function of time of incubation by immunohistochemistry using monoclonal antibody to BrdU. Compared to schistosomula cultured in the presence of RPMI plus 10% fetal calf serum, BLIs were increased by 60% in the presence of human portal, but not in peripheral serum. This stimulatory effect was substantially reproduced by a fraction of portal serum with a molecular weight range between 1 and 50 kDa. However, in the presence of human peripheral venous serum, either whole or fractionated, schistosomula showed no significant difference compared to RPMI plus 10% fetal calf serum alone. Furthermore, human portal serum fractions of molecular weight greater than 50 kDa also revealed no significant difference relative to control. The results indicate that portal venous serum component(s) of a molecular weight range higher than most simple nutrients can greatly stimulate the rate of cell proliferation of Schistosoma mansoni schistosomula.

A list is given of all habroneme species recorded from Australian birds, as well as a key to all known genera of Habronematinae. New species described are: Cyrnea (Procyrnea) dollfusi from Ninox novaeseelandiae; Cyrnea (Procyrnea) falco from Falco longipennis and F. berigora; Cyrnea (Procyrnea) spiralis from Philemon argenticeps, Entomyzon cyanotis, Oriolus sagittatus and Lalage sueuriitricolor; Excisa biloba from Podargus strigoides, Ninox novaeseelandia; Viguiera longicollis from Colluricinda rufiventris, C. harmonica, Anthochaera carunculata and Microeca fascinans; V. chibiae from Chibia bracteata; V. chabaudi from Podargus strigoides. Partial redescriptions are given of Cyrnea (Procyrnea) paraleptoptera (Johnson & Mawson) from the type specimens; Cyrnea (Procyrnea) mansioni from Falco berigora, Haliastur sphenurus, Astur novaehollandiae, and a ‘hawk’; Cyrnea (Procyrnea) sp. from a parrot, Psephotus haematonotus; Hadjelia truncata from Eurystomus orientalis; Hadjelia acuariana (s. Stellabronema acuariana Gushans-kaya) from Podargus strigoides; Torquatella balanocephala from Merops ornatus, and Torquatella sp. from Centropus phasianus.