All attempts hitherto made to infect different species of animals with P. canis have failed, and the remarkable fact remains that this parasite is apparently only communicable to dogs.

The following is an account of the anatomy of the scolex of Aporhynchus norvegicus (Olss.) involving details of the musculature and nervous and excretory systems. The anatomy of the strobila has been described by Nybelin (1918). The specimens, mostly young complete strobilae, were obtained from the intestine of Spinax spinax caught in the deep-sea fishing grounds to the west of Ireland. Until recently the species had only been recorded from the coast of Norway, but in 1936 Joyeux & Baer found it in French waters. It was first described as Tetrarhynchus norvegicus by Olsson (1867), the genus Aporhynchus being created by Nybelin (1918) for the single species.

Third-stage larvae of Pseudoterranova decipiens commonly infect whitefish such as cod, and the parasite can be transferred to humans through lightly prepared (sushi) meals. Because little is known about the nematode's cold tolerance capacity, we examined the nematode's ability to supercool, and whether or not cold acclimation could induce physiological changes that might increase its ability to tolerate freezing conditions. Even if third-stage Pseudoterranova decipiens larvae have some supercooling ability, they show no potential for freezing avoidance because they are not able to withstand inoculative freezing. Still, they have the ability to survive freezing at high subzero temperatures, something which suggests that these nematodes have a moderate freeze tolerance. We also show that acclimation to high temperatures triggers trehalose accumulation to an even greater extent than cold acclimation. Trehalose is a potential cryoprotectant which has been shown to play a vital role in the freeze tolerance of nematodes. We suggest that the trehalose accumulation observed for the cold acclimation is a general response to thermal stress, and that the nematode's moderate freeze tolerance may be acquired through adaptation to heat rather than coldness.

In recent work on the deposition of the epicuticle, Wigglesworth (1946) has shown that, in Rhodnius prolixus, not only is the epicuticle a composite structure comprising several distinct layers, but that the pore canals, which hitherto have been believed to terminate at the base of the epicuticle, do in fact penetrate its innermost regions. Wigglesworth extends the term epicuticle to cover the four outer layers of the cuticle in Rhodnius. The innermost of the four is a cuticulin layer which is followed by a polyphenol layer, a wax layer and an outer cement layer respectively. The pore canals penetrate the cuticulin layer.

It has already been shown (Imms, 1930) that the stem generation of the frit-fly in the Harpenden district is subjected to natural destruction, to a marked degree, by the agency of certain hymenopterous parasites. Among these, two species, viz. the Cynipid Rhoptromeris eucera Htg. and the Chalcid Halticoptera fuscicornis (Walk.) were found to predominate in numbers. Parasitisation, to a lower degree, by the Proctotrypid Loxotropa tritoma Thoms. was also noted and the Chalcid Callitula bicolor Spin. was recorded for the first time as having been reared from this same host. Evidence was also brought forward which o appeared to indicate that the parasitisation of frit-fly by the above combination of species increases in intensity as the season advances. In other words the stem generation of frit-fly, attacking late sown oats, is subjected to markedly heavier parasitisation than when it attacks oat sown earlier in the same season.

A number of studies had been conducted on rat species diversity in the Philippines, however, there is a dearth of information on the extent of Angiostrongylus spp. infection in various ecological niches. Collection of non-native rat samples occurred in various sampling sites categorized as residential, agricultural and agro-forest in Philippine Mount Makiling Forest Reserve (MMFR) and its adjacent areas . Three species of non-native rats were captured including Rattus tanezumi, Rattus norvegicus and Rattus exulans. Of the total 90 non-native rats collected, 24.4% were found infected with Angiostrongylus cantonensis. Statistical analysis showed significant difference among rat species with highest prevalence observed in R. exulans (42.9%) followed by R. tanezumi (29.8%) and R. norvegicus (7.7%) (P = 0.047). Angiostrongylus cantonensis infection was significantly higher in adults (29.4%) than in juvenile rats (9.1%) (P = 0.050). However, results showed no significant difference in A. cantonensis infection between male (43.3%) and female (18.3%) rats and between wet (31.6%) and dry seasons (19.2%) (P > 0.05). Moreover, this study also revealed that rats from agricultural and agro-forest areas showed significantly higher prevalence than residential areas. With urbanization and the everchanging landscape of MMFR watersheds and buffer zones, zoonotic transmission can pose health threats to the local people.

The regulatory role of tumour necrosis factor (TNF) was investigated in murine infection with tetrathyridia of Mesocestoides corti. Recombinant TNFα reduced macrophage larvicidal activity in vitro. M. corti primed mice for TNF release in response to bacterial lipopolysaccharide (LPS) in vivo. TNF activity was amplified 100-fold at 14 days post-infection (p.i.), with a further rise at day 28 p.i. Maximal inflammatory reaction was observed histologically in the liver at the height of TNF activity. Hepatic necrosis was located within inflammatory foci, but not within the vicinity of the parasite itself, suggesting that TNF may contribute to the pathogenesis of infection. Peritoneal cells from infected mice, when stimulated with tetrathyridia in vitro, showed a 4-fold increase in TNFα activity at day 14 p.i. However, when peritoneal cells were stimulated with LPS in vitro, a marked increase in TNFα secretion was observed at 2 months post-infection followed by a slow decline. It is suggested that impaired macrophage effector function, previously attributed to endogenous endotoxin, which gains access to peritoneal macrophages through an inability of the liver to detoxify endotoxin, may be mediated through TNFα.

Most compilers of our standard publications on parasitic Copepoda have described or figured species in an obviously mutilated condition, i.e. lacking the head or egg-strings.

The migration of infective nematode larvae into the tissues of their hosts has been proposed as a mechanism of reducing larval mortality and increase parasite lifetime reproductive success. Given that individual hosts differ in the level of exposure, strength of immune response and physiological conditions we may expect the number of larvae in tissue to vary both between and within hosts. We used 2 gastrointestinal nematode species common in the European rabbit (Oryctolagus cuniculus) and examined how the number of larvae in the tissue changed with the immune response, parasite intensity-dependent constraints in the lumen and seasonal weather factors, in rabbits of different age, sex and breeding status. For both nematode species, larvae from the gastrointestinal tissue exhibited strong seasonal and host age-related patterns with fewer larvae recovered in summer compared to winter and more in adults than in juveniles. The number of larvae of the 2 nematodes was positively associated with intensity of parasite infection in the lumen and antibody responses while it was negatively related with air temperature and rainfall. Host sex, reproductive status and co-infection with the second parasite species contributed to increase variability between hosts. We concluded that heterogeneities in host conditions are a significant cause of variability of larval abundance in the gastrointestinal tissues. These findings can have important consequences for the dynamics of nematode infections and how parasite's life-history strategies adjust to host changes.

In the Ascaroidea the germinal vesicle, the pronuclei and the nuclei of all the blastomeres prior to chromatin diminution are strongly Feulgen positive. The nuclei of the somatic cells, which become suddenly Feulgen negative upon chromatin diminution, gradually become strongly Feulgen positive again during subsequent development. The nuclei of the germ track cells which are not subjected to chromatin diminution remain strongly Feulgen positive during the whole development. In all the other metazoa, including the nematodes where chromatin diminution does not occur, the germinal vesicle, the synkaryon and the nuclei of the blastomeres during the earliest cleavage stages are Feulgen negative. The latter, however, become gradually strongly Feulgen positive again during the subsequent development. The nuclei of the female germ cells and the synkaryon of protozoa and plants have also been reported to be Feulgen negative. Thus, the Feulgen-positive nuclei of the definitive somatic cells always originate from Feulgen-negative nuclei, in the Ascaroidea from the Feulgen-negative nuclei of the blastomeres and in all other forms of life from the Feulgen-negative nuclei of the eggs. The Feulgen-positive nuclei of the germ cells also originate from Feulgen-negative nuclei except in the Ascaroidea, where they originate from Feulgen-positive nuclei. In the somatic track the sequence of Feulgen-positive nuclei is interrupted in all forms of life and during the germ track it is also interrupted in all forms of life except the Ascaroidea, where it is uninterrupted. These biologically important phenomena are discussed.

These investigations have been supported by a grant from the Knut and Alice Wallenberg stiftelse. The author is indebted to Mrs. M. Wahlström and E. Nowak for their valuable technical assistance.

Unsuckled mother rats given a 1 h suckling stimulus 3 h after subcutaneous injection of an exact dose of homogonic Strongyloides ratti allow fewer worms to develop in their intestines by day 8 than nulliparous rats (Wilson & Simpson, 1981). This effect is studied in more detail in terms of the length of time between weaning and stimulus (W → S) and injection and stimulus (I → S). It was observable with a W → S of 30 h but this and a period of 5 h were less effective than 24 h. With W → S constant at 24 h, significantly more worms developed in mothers when I → S was 24 h compared to 3 h and 10 h (P < 0·005). The data, combined with those from nulliparous controls, are presented as a measure of the change with time of numbers of larvae in that compartment of the system which gives access to the stimulated mammary gland. It is argued that the particular compartment is the local lymph node draining the injection site and that the kinetics deduced are applicable to migration in the rat in general

Transposons of the Mutator superfamily have been widely described in plants, but only recently have metazoan organisms been shown to harbour them. In this work we describe novel Mutator superfamily transposons from the genomes of the human parasites Schistosoma mansoni and S. japonicum, which we name Curupira-1 and Curupira-2. Curupira elements do not have Terminal Inverted Repeats (TIRs) at their extremities and generate Target Site Duplications (TSDs) of 9 base pairs. Curupira-2 transposons code for a conserved transposase and SWIM zinc finger domains, while Curupira-1 elements comprise these same domains plus a WRKY zinc finger. Alignment of transcript sequences from both elements back to the genomes indicates that they are subject to splicing to produce mature transcripts. Phylogenetic analyses indicate that these transposons represent a new lineage of metazoan Mutator-like elements with characteristics that are distinct from the recently described Phantom elements. Description of these novel schistosome transposons provides new insights in the evolution of transposable elements in schistosomes.

The four new species of Macropostrongylus Yorke & Maplestone, 1926, and the one new species of Pharyngostrongylus Yorke & Maplestone, 1926, which are described in this paper formed part of a collection of nematodes obtained by the Australian Institute of Tropical Medicine, and forwarded by Dr G. M. Heydon to the British Museum (Natural History). Co-type specimens will be deposited in both institutions.

Cephalobus parasiticus is described from eleven out of sixteen young specimens of Macacus irus mordax (synonym, M. cynomolgus) caught in the vicinity of Batavia.

The species, which strikingly resembles and is easily capable of being confused with the rhabditiform free-living generation of Strongyloides, is found in the stomach and intestine of the monkeys but is apparently non-pathogenic. This nematode appears to be unable to establish itself in the rat and guineapig but is capable of being propagated indefinitely on bouillon agar at room temperature.