All the known species of Solenopotes Enderlein, 1904 are discussed with a complete synonymy, major references, diagnoses, host associations and distribution; they are S. binipilosus (Fahrenholz, 1916a); S. burmeisteri (Fahrenholz, 1919); S. capillatus Enderlein, 1904; S. capreoli Freund, 1935a; S. ferrisi (Fahrenholz, 1919); S. muntiacus Thompson, 1938; S. natalensis Ledger, 1970 and S. tarandi (Mjöberg, 1915). The species of Solenopotes are compared on the basis of major taxonomic characters. Solenopotes and Linognathus are compared and a key to the known species of Solenopotes is also presented. Taxonomic relationships among the cervid-infesting species are quantitatively studied. The status of Linognathus panamensis Ewing, 1927, previously assigned to Solenopotes, is discussed and the species is redescribed and illustrated.

A comparative histochemical study is made on the distribution of succinate dehydrogenases, isocitrate dehydrogenases, malate dehydrogenases, glucose-6-phosphate dehydrogenases, α-glycerophosphate dehydrogenases, alcohol dehydrogenases, lactate dehydrogenases and glycogen phosphorylases in the tissues of sporocysts, rediae, cercariae and metacercariae parasitizing the gastropod mollusc Bithynia tentaculata. The results suggest that metabolic sequences resembling the conventional Embden–Meyerhoff pathway, the Pentose-Phosphate cycle and Krebs’ citric acid cycle may be operational in these larval digeneans. Heaviest enzyme activity is evident in the redial pharynx, the cercarial and metacercarial sucker and in the cercarial tail. Presumably the enzymes giving this heavy reaction form part of the energy producing mechanism for these active organs. Encysted metacercariae show a very heavy enzyme activity when compared with the sporocysts and developing cercariae of the same species. This is presumably associated with the breakdown of food storage materials, particularly glycogen, by these encysted stages.

Golden hamsters were given plerocercoids of Diphyllobothrium dendriticum either singly or in groups of 2, 4, 8 or 15. There was a higher rate of recovery of worms from hamsters given many (8 and 15) than from those given few (1, 2 or 4) plerocercoids. The difference in rate of recovery of worms was present from 2 h after administration of plerocercoids and persisted up to day 20 when experiments were ended. Denser tapeworm populations had the smallest individuals and some of them contained worms with primary strobilae at the start of egg production. The size of the tapeworm population did not influence the prepatent time. Also, with the common gull there was a higher rate of recovery of worms when plerocercoids were given in groups. These results are discussed in relation to aspects of the life-cycle of D. dendriticum where the natural final host is most probably normally infected by a larger number of plerocercoids at the same time.

Experiments are described which show that in a recently isolated field strain of the cattle nematode, Ostertagia ostertagi, the primary stimulus to the induction of inhibited development at the early fourth larval stage (EL4) in the host is chilling of the infective larvae (L3). Thus exposure of L3 to a temperature of 4 °C for 8 weeks prior to their oral administration to calves resulted in a mean of 66% of the established worm burden becoming inhibited at the EL4 stage. This provides an explanation for the seasonal occurrence in Britain of inhibited EL4 stages of O. ostertagi in cattle during the cold climate of late autumn and winter.

If the L3 stages were exposed to chilling for a prolonged period (> 19 weeks), prior to infection of calves, then the prevalence of inhibited EL4 stages amongst the worms established declined. After 33 weeks chilling the worm population consisted almost entirely of adults and only 2% inhibited EL4 stages. This suggested that a selective mortality of inhibition prone L3 was taking place and explained why under natural grazing conditions inhibition prone L3 were not available on the pasture in spring.

The duration of inhibition at the EL4 stage in calves infected with chilled L3 was consistently between 16 and 18 weeks and maturation of the majority of the inhibited larvae occurred spontaneously after such a period and irrespective of season. This period is equivalent to the duration of a normal winter in Britain when conditions unsuitable for the free living development of O. ostertagi larvae prevail.

The induction of inhibition by the environmental stimulus of chilling, the fixed period for the duration of inhibition within the host and the spontaneous maturation of the inhibited larvae are characteristic of a true diapause.

Adult Haemonchus contortus obtained from freshly killed sheep were incubated in a medium similar to Tyrode's saline containing known amounts of D-[U-14C]glucose. The worms appeared to remain in a healthy condition throughout the incubations which lasted for up to 6 h. All the radioactivity was recovered either within the worms or in the incubation vessel in the form of CO2, excretory products and unmetabolized glucose. An oxygen electrode in the incubation liquid showed that, because of their rapid oxygen consumption, the worms were under anaerobic conditions during all or nearly all of the incubation period, despite the presence of oxygen in the gas phase of the vessel. In terms both of quantity and radioactivity the main excretory products in solution were propan-1-ol, propionate and acetate. Smaller amounts of ethanol, lactate and succinate were excreted. Much radioactivity was associated with the expired CO2. At the end of the incubations glucose other than the initial radioactive glucose was detected indicating that the absorption of glucose by H. contortus is complex and needs further investigation. The present experiments suggest that the rate of absorption depends on the worm's need for nutrients. The results are compared with those found for other parasitic nematodes, particularly Ascaris lumbricoides, Heterakis gallinae and Trichuris vulpis. The importance of CO2 fixation in the utilization of energy from glucose by H. contortus is discussed.

An anthelmintic test was carried out in lambs against fourth-stage larvae of Haemonchus contortus to determine whether a natural loss of worms from either untreated control animals or from animals treated with anthelmintic affected the estimated activity of the anthelmintic.

Thirty-two lambs were each infected with 1500 larvae of H. contortus on 4 consecutive days and divided into 4 groups of 8 animals. Two groups of lambs were treated with anthelmintic on day 7, the first group being slaughtered on day 9 and the second on day 29. An untreated control group was slaughtered 7 days after infection and a second control group was killed 29 days after infection.

The numbers of worms recovered indicated that in the untreated control lambs there was an estimated daily loss of about 7% of the parasite population between the first day of infection and day 29, and in the lambs given anthelmintic an estimated daily loss of about 2% of the worm population was indicated between days 9 and 29. If the rate of worm loss is not the same in the untreated control hosts and in the treated animals, the estimate of anthelmintic efficacy will vary according to the time of autopsy. To minimize the possibility of an incorrect result occurring in an anthelmintic trial due to a natural loss of worms, it is recommended that the untreated control and the treated lambs are slaughtered on the same day, and that the autopsy is carried out as soon as possible after anthelmintic therapy.

A new coccidian parasite, Caryospora dendrelaphis sp.nov., with endogenous stages in the duodenal epithelium is described from the Australian colubrid snake Dendrelaphis punctulatus (Gray).

Diclidophora merlangi was found to consume oxygen under a variety of experimental conditions. The Qo2 of homogenates was 0.415 μl oxygen consumed/mg wet wt/h. Oxygen uptake was reduced in the presence of inhibitors: cyanide 0.1 mM and 5.0 mM, 100%; rotenone 10−6 M, 56%; antimycin A10−6 M, 63 %; malonate 10 mM, 36 %; arsenite 5 mM, 46 %; fluoroacetate 5 mM, 47 %. Worms died after 1 h incubation in 1 mM cyanide. It is suggested that these data provide evidence for the existence of a functional TCA cycle and respiratory chain of the classical pattern in this fluke.

In order to study egg release by Aspiculuris tetraptera total faecal collections from infected mice were made every 1½ h throughout successive 24 h periods. This was done with the aid of a histokinette machine. The cage containing the mice was suspended from one of the arms of the machine and every 1½ h the cage was moved on by the machine to the next adjacent collecting dish. The faecal pellets passed were counted and then used for flotation egg counts.

It was found that eggs were not released steadily and continuously and, in the case of the worms in an isolated mouse, egg output was clearly intermittent. Egg production did not appear to vary with the faecal production of the host in a consistent way but with two groups of 8 mice it was highest when faecal production was at its peak shortly before dawn. For the groups of 8 mice the concentration of eggs per faecal pellet was also highest at this time. In two experiments with an individual mouse, however, the egg counts fell to zero at dawn before the level of faecal production became reduced.

It is suggested therefore that egg output by female A. tetraptera may be stimulated by the altered physiological state of the host associated with feeding or general activity.

Of 63 specimens of the lizard Mabuya mabouya (Scincidae) examined in Pará State, Brazil, 31 showed one or more haemosporidians in the peripheral blood. These included Garnia (Plasmodium) morula (Telford, 1970), Lainson, Landau & Shaw, 1971; Plasmodium tropiduri and P. diploglossi Aragão & Neiva, 1909; a Plasmodium species close to P. diminutivum Telford, 1973a; and a new species of Saurocytozoon Lainson & Shaw, 1969a. Eleven different combinations of these parasites were noted, emphasizing the care needed in avoiding erroneous descriptions based on mixed infections. This is especially so when G. morula is mixed with P. tropiduri or other species with small, rounded gametocytes occupying a polar position in the red blood cells. Of 18 skinks infected with G. morula, 10 had pure infections, as judged by repeated examinations over long periods. The morphology of the Brazilian parasite is very similar to that described for G. morula from Panama (Telford, 1970): no malarial pigment could be demonstrated in any stage of the infection, including ookinetes and possible early oocysts which were studied in experimentally infected Culex pipiens fatigans. Ookinetes and rounded forms, possibly representing uninucleate oocysts, persisted in these insects up to 24 h after the blood-meal, but developed no further. C. p. fatigans is thus unlikely to be a natural vector of G. morula. Saurocytozoon mabuyi sp.nov. is described in M. mabouya: the gametocytes develop in the lymphocytes and monocytes of the circulating blood and reach maximum size in 19–28 days. The parasite can be distinguished from the other known species, S. tupinambi of the teiid lizard Tupinambus nigropunctatus, by its smaller gametocytes. Nothing is known of the sporogonic cycle. Differences between the sporogonic stages of S. tupinambi and Leucocytozoon are listed.

Lowland populations of the Plasmodium berghei group are compared with strains from the highlands of Katanga, Republic of Zaire, and it is concluded that the former warrant separate specific status. It is proposed that Plasmodium berghei yoelii of the Central African Republic be raised to a species, P. yoelii, and the lowland subspecies from the CAR, Brazzaville and Nigeria be moved to this species as P. y. yoelii, P. y. killicki and P. y. nigeriensis. P. berghei from Katanga would then revert to a monotypic species.

Differences between P. berghei and P. yoelii are in distribution, hosts, optimum temperatures of sporogony, sizes of mature oocysts and of sporozoites, rates of growth and minimum maturation times of tissue schizonts in the liver of the white rat, the forms of six enzymes and the DNA.

Differences between three subspecies of P. yoelii are in distribution, the sizes of mature oocysts and of sporozoites, sizes of tissue schizonts in the liver of the white rat, the effect of tissue forms on the nuclei of infected parenchymal cells and the electrophoretic forms of the enzyme GDH.

Adult Oesophagostomum columbianum populations were larger in sheep fed low-protein diets than in adequately fed animals. Diet did not influence the numbers of larva which became established in sheep. Sheep fed high-protein diets eliminated more worms and were more immunologically competent than poorly fed animals. More encapsulated larvae, showing arrested development, were found in adequately fed sheep than in those fed low-protein diets. Adult O. columbianum produced eggs at an earlier time after infection in poorly fed sheep than worms in well fed sheep. More eggs/female worm were produced in sheep on a low-protein diet compared with the number of eggs produced in well fed hosts over the last week of the infection. The effects of immunity on the behaviour of the worm in both host diet groups is discussed.

There was a greater cellular proliferation in the intestines of infected adequately fed sheep than in infected animals on low-protein diets. These changes were most pronounced in the large intestine where the adult parasites were found. The macrophage-lymphocyte series of cells underwent hyperplasia in well fed animals but these changes were reduced, particularly among the plasma cells, in sheep fed low-protein diets. Increased mucin and mast cell counts were observed in sheep on high-protein, but not in hosts on low-protein diets: the intestinal populations of eosinophil and globule leucocytes were also reduced in poorly fed sheep.

The relationship of these various cellular reactions and their effect on the protective immunity of sheep to O. columbianum is discussed. It was concluded that the increased susceptibility of protein deprived sheep to O. columbianum infections was associated with malfunctions of the innate immunity of the gut, involving decreased peristalsis and failure of the mucin cell response, and with reduction of the adaptive immune response which was reflected by impoverished lymphocyte and plasma cell reactions, and possibly with poor cooperation between sensitized lymphocytes, antibodies and the mast cell-granulocyte effector mechanisms in protective immunity.

A comparison of the oncomiracidia of the monogenean skin parasites Entobdella hippoglossi from the halibut (Hippoglossus hippoglossus), E. diadema from the sting ray (Dasyatis pastinaca) and E. soleae from the skin of the common sole (Solea solea) has revealed the presence of ‘body gland cells’, all of which have openings on the ventral or lateral surfaces of the larvae. In all three species there are two pairs of glands lying in the posterior region of the body proper with long ducts extending into the haptor and opening on its ventral surface. In addition to these two pairs of glands there are seven other pairs of body glands in E. hippoglossi, six pairs in E. diadema and two pairs in E. soleae. In E. soleae all the ‘body gland cells’ are poorly developed in the oncomiracidium and are more conspicuous in post-oncomiracidia. The fate of the ‘body gland cells’ during post-oncomiracidial development has been studied in E. soleae, and their possible functions are discussed. The glands in the head region (anterior median, posterior median and lateral head glands) are similar in all three species. Gland cells associated with the alimentary system are less easy to observe but differences between the three species appear to be small.

In the oncomiracidia of all three species the number of flame cells and their distribution are the same, but the oncomiracidia of E. hippoglossi and E. diadema have loops in the excretory ducts anterior to the bladder and the bladders of E. diadema contain refringent bodies.

The oncomiracidial eyes of E. hippoglossi and E. soleae have lenses but the lenses are greatly reduced in the oncomiracidia of E. diadema. In the three larvae there are small but characteristic differences in the shapes of the accessory sclerites.

The oncomiracidium of E. hippoglossi has not previously been described.