Both species of tick which are described in the present paper are members of insular faunas and demonstrate remarkably well the tendency, shown by these parasites in geographical isolation, to species formation. In this connexion it is perhaps worth quoting what Cooley & Kohls (1945) say concerning this subject in their recent work on the genus Ixodes: ‘These studies’, they write on p. 1 of their introduction, ‘have revealed in considerable measure the more useful specific characters and the importance of a real appreciation of the significance of geographical range and variation in the differentiation of species.… In determination of species limits we have considered not only morphologic but also biologic factors such as host relationships and geographic distribution. No subspecies are recognized.’ There is little doubt but that geographical distribution will be found to play an almost equally important role in the genus Amblyomma.

The tentacular bulb of Grillotia erinaceus metacestodes consists of obliquely striated muscle fibres with obvious motor end-plates. In this study isometric tension recordings and intracellular microelectrodes have been used to record mechanical and electrical activity from single isolated bulbs. Bulbs were mechanically quiescent and displayed resting membrane polentials (RMP) in the region of −49 to −64 mV with a mean RMP of −56 mV (n = 60). The membrane potential varied with [K+]o in a manner consistent with the RMP being determined largely by the K+ equilibrium potential. High K+ solution (> 15 mM) caused membrane depolarization and contraction of the preparation with the contraction showing both phasic and tonic components. L-glutamate caused membrane depolarization, contraction of quiescent preparations and increased the amplitude of electrically evoked responses. In contrast, 5-HT, dopamine, histamine, adrenaline, GABA, noradrenaline and D-glutamate, at concentrations up to and including 10−3 M, were without apparent affect, although acetylcholine, at relatively high concentrations (≥ 10−4 M) slightly reduced the amplitude of field-evoked contractions.

Large numbers of Plagiorchis (M.) megalorchis Rees, 1952, were found in the small intestine of dying pheasant chicks in Peeblesshire, Scotland. This is the first record of this trematode in pheasants. In one chick one specimen of Brachylaemus fuscatus (Rud, 1819) was found, which is a new host record in this country. Unusual virulence of these trematodes in pheasants and turkeys is noted, showing lack of adaptation to these hosts. In addition to chironomids and midge, culicine larvae were infected with cercariae from naturally infected Lymnaea pereger. It is proposed to consider P. laricola Skrjabin as described and illustrated by Chertkova (1953) to be Plagiorchis bikhovskayae n.nom.

The author wishes to express his thanks to R. H. Duff, M.R.C.V.S., of the Ministry of Agriculture, Veterinary Laboratory, Lasswade, for placing the first pheasant chicks at his disposal, and to A. Howe, the gamekeeper at Holylee, for his information and willing help.

1. The male of Rhipicephalus humeralis is redescribed and the female and immature stages are described for the first time. The synonymy of the species is discussed and the various stages are compared with those of R. pulchellus.

2. Details of the life cycle under laboratory conditions are given.

3. The host list and distribution of the species are given.

When beginning this investigation it was my intention to make a comparison between the anatomy of the apterous viviparous form and that of the winged viviparous form, to ascertain what differences were present corresponding with the difference in habit of the Aphis in these two stages. I found, however, that the literature bearing on the group to which S. rosarum belongs, was somewhat scanty, and as a rule, rather out of date. It therefore became necessary, before undertaking the comparative work, to obtain a somewhat more complete account of the general anatomy. It is with this idea in view that the following paper has been written; but, as will be seen on perusing it, much more attention has been given to the internal anatomy than to the external parts. It is my intention, now that this first part of the task is completed, to take up my original project. I desire to take this opportunity of expressing my gratitude to Professor Bridge, Mr A. E. Shipley, F.R.S., Mr Doncaster and Mr Collinge for the valuable assistance and advice they have given me whilst this work has been in progress.

Environmental fluctuations are expected to require special adaptations only if they are associated with a decrease in fitness. We compared reproductive performance between fleas fed on alternating (preferred and non-preferred) hosts and fleas fed solely on either a preferred or a non-preferred host to determine whether (1) host alternation incurs an immediate negative effect, and, if yes, then (2) whether this effect is greater in a host specialist (Parapulex chephrenis) than in host generalists (Xenopsylla conformis and Synosternus cleopatrae). We also compared flea performance under alternating host regimes with different host order (initial feeding on either a preferred or a non-preferred host). An immediate negative effect of alternating hosts on reproductive performance was found in P. chephrenis only. These fleas produced 44·3% less eggs that were 3·6% smaller when they fed on alternating hosts as compared with a preferred host. In contrast, X. conformis and S. cleopatrae appeared to be able to adapt their reproductive strategy to host alternation by producing higher quality offspring (on average, 3·1% faster development and 2·1% larger size) without compromising offspring number. However, the former produced eggs that were slightly, albeit significantly, smaller when it fed on alternating hosts as compared with a preferred host. Moreover, host order affected reproductive performance in host generalists (e.g. 2·8% larger eggs when the first feeding was performed on a non-preferred host), but not in a host specialist. We conclude that immediate effects of environmental fluctuation on parasite fitness depend on the degree of host specialization.

As a consequence of axenic growth and the elimination of accompanying bacterial flora, Entamoeba histolytica virulence decreases rapidly, and pathogenicity is lost. This paper evaluated the impact of vitamin supplementation on the pathogenicity of E. histolytica. Growth of E. histolytica trophozoites, cultured axenically in PEHPS (a Spanish acronym for the main ingredients – casein peptone, liver, pancreas extract and bovine serum) medium, with or without vitamins, exhibited a similar growth rate. However, the vitamin-enriched PEHPS preparations expressed 2.65 times more haemolytic activity (at 60 min: 98 vs 48%, P < 0.05), 2.5 times more phospholipase A2 activity at 150 min of incubation and generated more hepatic abscesses (88 vs 60%, P = 0.05) than the preparations without vitamins. The haemolytic and phospholipase A2 activity for the PEHPS − V preparations were restored following vitamin supplementation with A and D. These data highlight, for the first time, that vitamins and specifically vitamin A and D were essential for the recovery of amoebic virulence, lost through axenic growth.

The inheritance of an antigen designated Py-1 in the rodent malaria parasite Plasmodium yoelii has been investigated. A cross was made between 2 lines differing in the electrophoretic mobility and quantity of Py-1 detected by crossed immunoelectrophoresis. In 10 clones isolated from the progeny of the cross the level of Py-1 always correlated with the virulence of the infection and it was concluded that these characters were different phenotypic effects of the same gene mutation. The electrophoretic mobility of Py-1 segregated independently of the virulence character and was therefore controlled by a different gene. These two antigenic markers also recombined with isoenzyme and drug-sensitivity characters distinguishing the parent lines.

Male: Large, 4·00–7–75 mm. long. Salient features: Inornate; basis capituli nearly twice as broad as long; lateral angles within the anterior third and rather acute. Anterior coxae slightly prominent in dorsal view. Lateral grooves well-marked and including two festoons. Dorsal furrows distinct, the lateral somewhat comma-shaped, the median straight and continued anteriorly beyond the laterals. Punctations very numerous, usually discreet and equal in the median area which appears shagreened; few on the scapulae, lateral folds and festoons, which form a glossy border. Adanal plates with straight external border and broad, rounded posterior border; internal border slightly concave to where it joins the posterior border to form a small point in a number of specimens. Accessory plates distinct. Spiracle short with slight dorsal curve.

In a collection of the early stages of Simuliidae, made by Mr F. W. Edwards, in the summer of 1923, from the rapids above Tännforsen waterfalls, Sweden, there are representatives of 11 species of Simulium: larvae and pupae of S. venustum Say and S. tredecimatum Edw., larvae of S. morsitans Edw. and S. reptans var. galeratum Edw., pupae of S. tuberosum Lundstr., larvae and pupae of S. pusillum and pupae of S. pallipes Fries and S. lyra Lundstr., besides pupae of three other indeterminable species. In a previous paper I have already described, in detail, the early stages of the first five species, and in the present paper I deal for the first time with the remaining six species and the early stages of S.ferruginum Wahlgr. The pupae of S. pusillum Fries, S. pallipes and S. lyra were identified by Mr Edwards, by dissecting out the male genitalia, but those of the remaining three species, herein described as species I–III, are indeterminable owing to their immaturity. It seems inadvisable to give the pupae new specific names as further investigation may prove that they belong to well-known Continental species.

A murine AIDS model with many similarities to human AIDS, LP-BM5 Murine Leukaemia, suppresses T and B cell numbers and functions in the intestine. This permits chronic colonization by Giardia and Cryptosporidium. Cocaine and the nutrient alcohol, which are immunosuppressive, further reduce resistance to intestinal parasites and intestinal lymphocyte numbers. Protein undernutrition, vitamin E supplementation, and alcohol use further modify immune dysfunction induced by the murine retrovirus infection. This suggests that both undernutrition and nutrient supplementation could affect parasite resistance during AIDS. Thus this murine model of human AIDS has great potential to accelerate studies of the role of nutrients in immune dysfunction and resistance to intestinal parasites.

Modern chemical insecticides revolutionized the fight against vector-borne diseases during the period following the Second World War. They are extensively used at present for that purpose and will very likely continue to play an important role in the foreseeable future. However, these insecticides have their limitations.

Confocal scanning laser microscopy has been used to study the distribution of antigens expressed by the liver stages of Plasmodium berghei in cultured hepatoma cells. The 3-dimensional images obtained of intact parasites clearly show complex patterns of antigen expression not apparent when using conventional IFAT or immunoelectron microscopy. A liver-stage specific antigen (Pbl 1) was shown to be confined to the parasitophorous vacuole; the vacuole has extensive diverticulae extending into the host cell. Small parasites were detected for the first time in ‘mature’ cultures. These did not represent a distinct population, but the ‘tail’ of a broad continuum of parasite sizes. Irradiated sporozoites produce a transient population of slow-growing parasites which express a very limited range of antigens de novo in the invaded hepatoma cell. A comparison of the reactivity of text-abstract EE parasites with anti-circumsporozoite antibody and with anti-Pbl 1 suggests that the former reagent may reliably be used to identify sporozoites invading host cells, but should not be used to determine the number of parasites that successfully undergo intrahepatic development. Anti-Pbl-1 indicates on 33% of invaded sporozoites identified by anti-CSP subsequently differentiate.

Habitat and material. By the courtesy and at the request of Prof. Vladimir Ebathof of Archangel I have been enabled to examine and describe two female copepods belonging to a new genus and species of the family Lernaeopodidae, consigned to him as taken from the gills of Rhyncodon typicus Smith caught in 1913 in the Pacific between China and south-west Japan. One specimen, drawn to scale (Fig. 1), was twice the size of the other.

Apicomplexan parasites have unconventional actins that play a central role in important cellular processes such as apicoplast replication, motility of dense granules, endocytic trafficking and force generation for motility and host cell invasion. In this study, we investigated the actin of the apicomplexan Neospora caninum – a parasite associated with infectious abortion and neonatal mortality in livestock. Neospora caninum actin was detected and identified in two bands by one-dimensional (1D) western blot and in nine spots by the 2D technique. The mass spectrometry data indicated that N. caninum has at least nine different actin isoforms, possibly caused by post-translational modifications. In addition, the C4 pan-actin antibody detected specifically actin in N. caninum cellular extract. Extracellular N. caninum tachyzoites were treated with toxins that act on actin, jasplakinolide and cytochalasin D. Both substances altered the peripheric cytoplasmic localization of actin on tachyzoites. Our findings add complexity to the study of the apicomplexan actin in cellular processes, since the multiple functions of this important protein might be regulated by mechanisms involving post-translational modifications.

The original description of Ixodes tatei was given by Arthur (1959) and based on three females taken from a rock partridge of unknown species and from a fox (Vulpes sp. ?) in Jarmo, Chemchemal Valley, Kirkuk (type locality) and the Zagros Mountains, Erbil, both in north-eastern Iraq. The material, on which the following account is based, consisted of two females, one gorged nymph, one slightly fed nymph and two fully gorged larvae. They were collected from the head of Alectoris graeca, which was shot about 20 km south of Jerusalem on 17 December 1966 and sent to me by Professor O. Theodor of the Hebrew University. One female, one nymph and one larva have been deposited in the Hebrew University, Hadassah Medical School, and one female, one nymph and one larva are retained in my collection. The holotype female is deposited in the Chicago Natural History Museum, Cat. no. 84472.

The parasite herein described was found in the coelomic cavity of Culicoides peregrinus by Mr A. R. O. Smith, of the Calcutta School of Tropical Medicine and Hygiene, and was brought to me for identification. It is named after the Teacher of Protozoology, Calcutta School of Tropical Medicine. Numerous specimens with several undergoing ordinary transverse fission were observed.

In the paper on the association of Rickettsia with Trench Fever, by Arkwright, Bacot and Duncan (1919) mention is made of a bacillary infection of the excreta and guts of lice (Pediculus humcmus). A Gram-negative cocco-bacillus was isolated in pure culture. It was non-motile, fermented glucose, mannite and lactose very slowly, and formed acid and clot in milk in about 14 days.

When specimens of the turtle, Trionyx gangeticus, and of the fish, Wallago attu, were purchased in a local market and examined, nematodes were found in the intestines of both these hosts. Two males were found in the intestine of the turtle, and a male and three females in the intestine of the fish. Examination of these nematodes showed that they all belonged to the genus Dichelyne Jägerskiöld, 1902, but that none of them belonged to any known species of this genus. The genus Dichelyne was regarded by Yorke & Maplestone (1926) as being synonymous with the genus Cucullanus, O. F. Mueller, 1777, but was later re-instated as a distinct genus by J. F. Mueller (1934), who reduced the genus Dacnitoides Ward & Magath, 1916, to synonymy with Dichelyne. In the light of these emendations the genus Dichelyne now includes the following species: D. fossor Jägerskiöld, 1902, 1909; D. cotylophora (Ward & Magath, 1916), J. F. Mueller, 1934; D. robusta Van Cleave & Mueller, 1932; D. fastigatus Chandler, 1937; and D. diplocaecum Chandler, 1937.