Host and Record. A single female was found attached close to the left pelvic fin of a Histiophorus brevirostris Playfair caught off the south-west coast of Ceylon in January, 1932. One of the egg-strings was missing.

The infective larvae of S. ratti were non-feeding and none of a wide variety of possible substrates had any effect on the respiratory rate of intact worms. Sodium succinate increased the oxygen uptake of larval homogenates.

The cytochrome chain inhibitors, sodium cyanide, sodium azide and urethane all reversibly inhibited the respiration of the infective larvae. The inhibition caused by carbon monoxide was photo-reversible and 2,4-dinitrophenol inhibited respiration rather than stimulated it. Methylene blue increased the oxygen uptake of homogenates, but had no effect on the intact larva. Iodoacetamide and sodium arsenite irreversibly inhibited respiration, whilst sodium fluoride, sodium pyrophosphate and sodium malonate were without effect on the intact larvae.

This work was carried out during the tenure of a Medical Research Council Scholarship.

Six stocks of Trypanosoma congolense were cloned from 17 stocks isolated from Eastern Zambia and used to initiate insect-form in vitro cultures producing metacyclic trypanosomes. Serological assays were then developed using these in vitro-derived metacyclics as a reference collection of antigens. Monoclonal antibodies recognized 8 metacyclic variable antigen types (M-VATs) of one stock, T. congolense TREU 1885, representing 70–80% of that stock's M-VAT repertoire, and in an indirect fluorescent antibody test (IFAT) there were no cross-reactions between them and the metacyclic trypanosomes of the other 5 stocks. Cross-protection assays between the 6 stocks in mice showed that the stocks cultured in vitro were serologically distinct. In order to facilitate serological typing for serodeme characterization, an IFAT was developed using formalin-fixed metacyclic trypanosomes to identify VAT specific immune responses using 21 day post-infection antisera. The cultured stocks reacted only with their homologous antisera thus confirming the results obtained in the cross-protection assays. No cross-reactions were observed with the 6 cloned stocks and antisera against the 11 stocks of T. congolense isolated in the same area at the same time suggesting that these stocks were different from the reference collection of cultured metacyclics. Hence, at least 7 serodemes of T. congolense have been identified from the 17 stocks isolated.

This paper describes a compartmental model incorporating biological details of the transmission of canine visceral leishmaniasis in southern France. In contrast to earlier, empirical models (Jolivet, 1977; Rioux, Croset & Lanotte, 1977) the new model (1) predicts a threshold density of sandflies below which transmission cannot be sustained, (2) suggests that, until better data become available, the maximum prevalence of infection obtained at high sandfly density should be considered an unknown quantity.

The tegument of the metacercaria of Gorgoderina vitelliloba contains S1, S2, S3 and S4 secretory bodies. Between the parenchymal cells 2 types of tegumental cyton occur. Type 1 contains S1 and S3 secretory bodies, whilst S2 and S4 bodies are limited to Type 2. Type 1 cytons and S1 secretory bodies disappear at excystment. Post-metacercariae contain a third type of tegumental cyton in which a new secretory body, S5, occurs. This cyton type disintegrates 1–5 days after infection. The maintenance and development of the outer anucleate layer after this period is the responsibility of Type 2 cytons. Type 2 cytons and S2 and S4 secretory bodies have also been found within the cercarial body. When juvenile flukes migrate from the kidney to the bladder of their frog definitive host 21 days after infection, the outer anucleate layer increases in electron density. Within the bladder, however, the tegument of the adult fluke appears normal. The distribution of mitochondria within the outer anucleate layer changes during the fluke's migration. The mitochondria, which have a random distribution in the metacercaria, are located adjacent to the outer and basal plasmalemmas in the early kidney stages. In late kidney stages and bladder stages mitochondria occur only against the former membrane. The mitochondria increase in size in the adult fluke.

Metacestodes of Hymenolepis diminuta affect several aspects of female reproductive physiology in Tenebrio molitor and such effects are mediated via the endocrine system. The effects on male reproduction are less well known and were studied with respect to the Bean-Shaped Accessory Glands (BAGs). The size and wet and dry weight of BAGs from infected and uninfected beetles were compared and rose to a plateau from 0–6 days post-emergence in uninfected beetles but in infected individuals continued to increase in both size and weight. These effects were density independent. Glands from both infected and uninfected beetles were assayed for trehalase activity measured by its ability to convert the sugar trehalose to glucose. The activity of this enzyme, per mg wet weight, was not affected by the parasite. However, total activity per gland increased in infected males. Total protein content and electrophoretic profiles of BAGs from infected and uninfected individuals showed no change in profile but showed an increase in all protein subunits per gland over a broad molecular weight range.

1. A method, based on that devised for E. histolytica by Dobell (1947), was worked out for testing the action of drugs upon E. invadens.

2. The sensitivity of di- and monobacterial strains of E. invadens to emetine was determined, and of a dibacterial strain to the quinaldines A 352, A 356 and A 404. E. invadens was killed by emetine at concentrations of 1/50,000–1/100,000, A 352 or A 356 at 1/100,000, and A 404 at 1/10,000. The strains of E. invadens used in the present tests are thus less sensitive to emetine than is E. histolytica, but the sensitivity of the two species to the quinaldines is similar.

3. A strain of E. invadens which was maintained for 9 months in the presence of increasing concentrations of emetine, did not become resistant to the drug.

I am indebted to Dr A. Bishop for much advice and criticism; to Dr J. D. Fulton for a culture of Bacterium coli A'; and to Dr J. Walker for supplies of the compounds A 352, A 356 and A404. The work has been financed by the Medical Research Council.

Anguillicola crassus is the most invasive species of its genus and it is a successful colonizer of different eel species worldwide. It is so far the only species of the genus Anguillicola whose life cycle has been studied completely. To analyse whether differences in life cycle may explain differences in invasiveness, we infected European eels with Anguillicola novaezelandiae under laboratory conditions. Anguillicola novaezelandiae shows a synchronized development in the European eel. Eggs with second-stage larvae appeared 120 days after infection. No density-dependent effect in parasite development could be found for A. novaezelandiae. The present study shows that the life cycle of A. novaezelandiae differs on final host level compared with A. crassus in ways which result in a less successful invasion of new host species.

The intimate cell relationships of Hymenolepis diminuta are described and occur between cells of the parenchyma, excretory system, muscle and tegument. The cell relationships are of three types: (a) a tight junction or zonula occludens; (b) a desmosome-like structure without tonofibrils or intercellular dense line; (c) a junctional complex with modified unit membranes and an intercellular region of dense granules and fibres.

This research was begun while one of us (L.T.T.) was a Visiting Lecturer in the Biology Department, Rice University, and completed in the Zoology Department, Queen's University, Belfast. We should like to thank Dr C. W. Philpott for allowing us the full use of the facilities of his electron-microscope unit and Mr W. Ferguson for photographic assistance.

Invasive parasites can spill over to new hosts in invaded ecosystems with often unpredictable trophic relationships in the newly arising parasite-host interactions. In European seas, the intestinal copepod Mytilicola orientalis was co-introduced with Pacific oysters (Magallana gigas) and spilled over to native blue mussels (Mytilus edulis), with negative impacts on the condition of infected mussels. However, whether the parasite feeds on host tissue and/or stomach contents is yet unknown. To answer this question, we performed a stable isotope analysis in which we included mussel host tissue and the primary food sources of the mussels, microphytobenthos (MPB) and particulate organic matter (POM). The copepods were slightly enriched in δ15N (mean Δ15N ± s.d.; 1·22 ± 0·58‰) and δ13C (Δ13C 0·25 ± 0·32‰) with respect to their host. Stable isotope mixing models using a range of trophic fractionation factors indicated that host tissue was the main food resource with consistent additional contributions of MPB and POM. These results suggest that the trophic relationship of the invasive copepod with its mussel host is parasitic as well as commensalistic. Stable isotope studies such as this one may be a useful tool to unravel trophic relationships in new parasite-host associations in the course of invasions.

Plasmodium knowlesi malaria-infected erythrocytes were radio-iodinated and several non-ionic, anionic and zwitterionic detergents were compared in their capacity to extract the labelled membrane proteins. The use of these detergents for antigen identification was tested by immunoprecipitation, after addition of Triton X-100 to some detergent extracts, using hyperimmune monkey antiserum and protein A-Sepharose. 125I-labelled antigens were specifically immunoprecipitated with all detergents tested, including the anionic detergents sodium dodecyl sulphate (SDS), deoxycholate and cholate; the zwitterions Zwittergent-312 and -314, CHAPS and Empigen BB, as well as several non-ionic detergents. The SDS-polyacrylamide gel electrophoresis patterns of 125I-labelled antigens varied after extraction with different detergents, there being no consistent pattern for detergents of a particular class. A total of 14 125I-labelled antigens were identified, 11 of them using Triton X-100. Some minor antigens identified with Triton X-100 were immunoprecipitated in greater amount after extraction in other detergents. Most importantly, two antigens Mr 200000 and 180000 were detected only after extraction with deoxycholate or SDS.

Direct surface I radio-isotope labelling techniques and SDS—PAGE analysis were used to compare the proteins and lentil—lectin adherent glycoproteins of the bovine stage of viable Taenia saginata larvae at three points in their development, the invasive oncospheres, immature (4-week-old) and mature (12 to 16-week-old) cysticerci. Some proteins and glycoproteins were present on all three of the ages of the parasite examined but there were also distinct age-specific proteins and glycoproteins detected on oncospheres and 4-week-old cysticerci and a marked difference between the protein/glycoprotein profiles of the parasite was apparent at these earlier stages of development and the mature cysticerci. The latter were characterized by the presence of high, 160–200 kDa molecular weight, lysine rich, glycoproteins, whereas small 16 and 18 kDa glycoproteins and a reduction-sensitive 23 kDa glycoprotein were first detected on 4-week-old immature cysticerci. Antigenic characterization of the isotope-labelled proteins and glycoproteins by immunoprecipitation against a panel of clinically defined bovine sera combined with SDS–PAGE analysis indicated that relatively few proteins were precipitated by sera from T. saginata-infected cattle as compared to the glycoproteins. However, both protein and glycoprotein antigens of possible protective and/or diagnostic significance were identified from oncospheres and cysticerci.

This study was conducted to identify surface antigens of the microfilarial sheath of Litomosoides carinii which are accessible to antibodies. Rabbit antisera were raised against the soluble and insoluble fractions of purified sheaths by extracting them with a buffer containing 2-mercaptoethanol and sodium dodecylsulphate. These sera and rabbit hyperimmune sera directed against homogenates of total microfilariae, mature (i.e. microfilariae liberating) female parasites and excretory–secretory products of adult females were able to agglutinate live and formaldehyde-fixed microfilariae. When the antisera directed against sheath constituents were administered to patently infected Mastomys coucha, the microfilaraemia of these animals was rapidly reduced and remained low for a period of 2–3 weeks. Antibodies specifically binding to the microfilarial surface were immunoaffinity-purified on formaldehyde-fixed microfilariae. The antibodies react with sheath antigens of 40 and 120 kDa molecular mass which are produced by the epithelium of the distal uterus of the mature female, secreted and attached to the surface of the sheaths. A 120 kDa antigen recognized by anti-sheath surface antibodies was also detected in the excretory–secretory products of in Vitro-cultured immature female L. carinii from day 30 post-infection onwards. In the excretory–secretory products of mature adult female parasites recovered on day 130 post-infection, this 120 kDa molecule was absent. However, material reacting with the antibody was detected in the stacking gel of SDS-polyacrylamide gels. This finding may indicate that the basic units forming the 120 kDa antigen of immature adults or microfilarial sheath surface antigens occur in a highly polymerized form in the excretory–secretory products of mature female parasites.

Early this year (1932) we examined eight American raccoons (Procyon s. Notocyon lotor) whose faeces, according to Darling, contained Coccidia of our species.

In the present study, the diagnostic value of Trypanosoma cruzi recombinant protein (Tc24) was examined. Although antibodies against Tc24 were detected during natural and experimental T. cruzi infections, specificity studies revealed that sera from T. rangeli-infected mice also recognized to some extent Tc24 protein. In addition, sera from Tc24-immunized mice reacted against a 21 kDa polypeptide in T. rangeli extracts. Detailed analysis of the antibody response against 20—40 peptide localized in the Tc24 amino-terminal domain suggests that this sequence is not expressed by T. rangeli 21 kDa antigen. Therefore, the PCR reaction using oligonucleotides corresponding to a 20–26 peptide clearly demonstrated the specificity of the oligoprobes for T. cruzi identification. Positive signals were also found when using blood samples from T. cruzi-infected mice. Taken together, these results suggest that the PCR-based 20–26 assay may be useful in the specific diagnosis of Chagas' disease.

Considering that both infection and dominance status can be conveyed through urinary odours and both are thought to affect mate choice, the present study assessed the role of infection and male dominance status on female mate choice in arena enclosures. Three male CD-1 mice were simultaneously introduced into each of 4 spatially complex arenas (3·0×0·6×0·4 m high) for 24 h prior to introduction of 5 females into each arena. During the first mating sequence (i.e. Mating 1), all 3 males were uninfected. Prior to Mating 2, the dominant male in each arena was infected with 200 L3 of Heligmosomoides polygyrus (Nematoda). Prior to Mating 3, the dominant male was drug-treated to remove the parasite. Dominance was assessed by the absence of rump or tail wounds (Freeland, 1981). Females were removed from the arena when visibly pregnant, and returned for subsequent mating 2 weeks following parturition. Paternity was determined by microsatellite analysis of each pup. Multi-male mating (i.e. mating with 2 or all 3 males) was a common strategy among females as littermates were sired by 2 or all 3 males in 64% of the litters. Contrary to expectation, the dominant male did not sire the majority of offspring in any of the mating sequences, and infection and subsequent drug treatment of the dominant male did not have a significant impact on female mate choice. In addition to methodological differences in paternity determination (i.e. DNA analysis versus behavioural observations and/or phenotypic traits), these findings may be further explained by the spatial complexity of the experimental arenas.

1. The distribution of filarial larvae in the dorsoventral and dorsal-longitudinal muscle fibre groups was studied in serial sections of mosquitoes of a susceptible strain of Aedes aegypti infected with Brugia pahangi or subperiodic B. malayi and of wild-caught Mansonia uniformis mosquitoes containing the latter parasite.

2. The experiments showed that more larvae were situated in the dorsal-longitudinal muscle than in the dorsoventral and that the difference in numbers was highly significant.

In September, 1908, an opportunity was afforded me of examining some of the larger food-fishes brought in to Aberdeen fish market. For this I have to thank the courtesy of Professor J. Arthur Thomson, who kindly provided the necessary laboratory accommodation, and was of great assistance to me in various other directions. I have also to thank the Government Grant Committee of the Royal Society for defraying the expenses of procuring specimens.