Habitat and record. I am much indebted to Miss Miriam Rothschild for kindly presenting me with a female specimen of a new cymothoid isopod taken from the mouth of a fish known locally as Boca-Chica, which, in the words of the collector, is “slightly larger than a herring, scaled, and with a sucker-like mouth”, probably a loricariid, from Rio Napo, Ecuador.

Myxozoans are parasitic, microscopic cnidarians that have retained the phylum-characteristic stinging capsules called nematocysts. Free-living cnidarians, like jellyfish and corals, utilize nematocysts for feeding and defence, with discharge powered by osmotic energy. Myxozoans use nematocysts to anchor to their fish hosts in the first step of infection, however, the discharge mechanism is poorly understood. We used Myxobolus cerebralis, a pathogenic myxozoan parasite of salmonid fishes, and developed two assays to explore the nature of its nematocyst discharge. Using parasite actinospores, the infectious stage to fish, we stimulated discharge of the nematocysts with rainbow trout mucus in vitro, in solutions enriched with chloride salts of Na+, K+, Ca2+ and Gd3+, and quantified discharge using microscopy. We then used quantitative polymerase chain reaction to evaluate the in vivo effects of these treatments, plus Mg2+ and the common aquaculture disinfectant KMnO₄, on the ability of M. cerebralis actinospores to infect fish. We found that Mg2+ and Gd3+ reduced infection in vivo, whereas Na+ and K+ over-stimulated nematocyst discharge in vitro and reduced infection in vivo. These findings align with nematocyst discharge behaviour in free-living Cnidaria, and suggest phylum-wide commonalties, which could be exploited to develop novel approaches for controlling myxozoan diseases in aquaculture.

Antigenic variation is a powerful survival strategy adapted by certain species of parasitic protozoa to allow them to survive in the immunized host. It is exemplified by the African trypanosomes, which provide far and away the best characterized and most studied system of this kind. Why have the trypanosomes developed antigenic variation to such a sophisticated level? Because the trypanosome lives its life in the bloodstream of its mammalian host and is therefore in continuous conflict with the host's immune system. Antigenic variation represents its whole survival strategy, with some help provided by its ability to immunosuppress the host. The importance of antigenic variation to the trypanosome is underscored by the estimate that up to 10% of the trypanosome genome may be devoted to variant antigen genes (Van der Ploeg et al. 1982). Most other parasitic protozoa prefer a less confrontational existence and usually adopt an intracellular home for at least a part of their life-cycle within the mammalian host. That being the case, do other parasitic protozoa need antigenic variation within their armorarium ? The answer seems to be yes, although the reasons why are by no means clear. For example, the stages in the life-cycle which exhibit antigenic variation might be expected to be those which are released free into the bloodstream – in malaria, sporozoites and merozoites, for example. Yet there seems to be no evidence for phenotypic variation at all in these stages. Rather, it is the intracellular stages which, in both Plasmodium and Babesia, seem to elaborate molecules which are expressed at the surface of the parasitized cell, and which are capable of both eliciting an immune response and of avoiding the con- sequences of such a response by phenotypic antigenic variation. Why are such antigens expressed, and what is their functional significance?

The material of the species to be described was found in a small collection of parasites from Zanzibar, placed at my disposal by Professor G. H. F. Nuttall, F.R.S., to whom I wish to express my thanks. As only a few cestodes have hitherto been recorded from East Africa and its helminth fauna is therefore largely unknown, a list of the forms identified is given at the end of the paper. I desire to acknowledge my indebtedness to the Birmingham Natural History and Philosophical Society for a grant towards the expense of preparing the plates, both in this and the preceding paper (Parasitology, XIII. No. 1, March 1921, p. 1).

Es ist schon längst die weit verbreitete Hautkrankheit des Menschen bekannt, welche in Russland bildlich als “Wolossatik” bezeichnet wird. Dieser Volksname findet seine Erklärung im Aberglauben der Bauern, welche überzeugt sind, dass ein ins Wasser gefallenes Pferdehaar auflebe (Verwechselung mit dem Gordius aquaticus). In solchem Zustande solle es manchmal beim Baden oder Waschen in die Haut des Menschen eindringen, wo es sich bewegt, ein Jucken verursacht und in der Haut eine rötliche, leicht angeschwollene Spur resp. eine mehr oder weniger gewundenen Linie hinterlassen kann. Diese Krank-heit wurde beschrieben (1) von Lee, welcher in der Clinical Society of London, 1874, einen Vortrag über einen Fall der Kriechkrankheit (Creeping eruption) gehalten hat, und (2) von Samson, welcher 1895, in Wratsch einen Brief über eine neue Hautkrankheit veröffentlicht hat. Auf Samson's Brief folgten bald analoge Mitteilungen Ssokolow (1895), Kuschen (1896), Olissow (1897), Kum-berg (1898), Rownitzky (1898), Wostrikow und Bogrow (1909) in Russland und Lee (1884), Malcolm Morris (1896), Neumann (1895), Kaposi (1898), Harlingen (1902), Boas (1907), Fülleborn (1908, 1918), Knowles (1916), León (1914) u. a. in West-Europa und Amerika.

1. Four species had been described to date as belonging to the genus Catoptroides: C. spatula and C. spatulaeforme from African catfish and C. macrocotyle and C. angulatus from European fish.

2. C. lacustri, a new species described in this paper, was taken from the great fork-tailed catfish, Ameiurus lacustris, from the St Croix River, Minnesota.

3. To this list must be added C. staffordi of the American catfish, Ameiurus nebulosus and A. melas, which was described by Pearse in 1924 and placed in the genus Phyllodistomum.

4. C. angulatus is shown not to be a member of this genus, but rather as belonging to the genus Phyllodistomum in which von Linstow first described it.

5. All of these species are briefly reviewed and compared in this paper.

Although the common Filariid parasite of the Camel was identified as a distinct species more than forty years ago (Lewis, 1882), the recent memoir on Indian Nematodes by Baylis and Daubney (1923) contains the first intelligible account of the structure of the adult worm. Their description of the species, which they refer to the genus Acanthocheilonema, is based partly on some rather fragmentary material received from the Zoological Survey of India, and partly on notes and drawings supplied by Major F. H. Stewart, I.M.S.

Two new species of Lepeophtheirus are described and illustrated based on a collection from the Orange County sewer outfall, California. They are: L. remiopsis sp.nov. from the branchial cavities and external body surfaces of Parophrys vetulus Girard, Hippoglossina stomata Eigenmann & Eigenmann, Pleuronichthys verticalis (Jordan & Gilbert), Chitonotus pugetensis (Steindachner), and Porichthys notatus (Girard); and L. rotundipes sp.nov. from the external body surfaces and occasionally the gill cavities of Scorpaena guttata (Girard) and Citharichthys stigmaeus Jordan & Gilbert.

The human malaria parasite, Plasmodium falciparum, is currently being actively studied by molecular biologists. It is hoped that the use of recombinant DNA techniques in this area will give new insights into the biology of the organism and, at the same time, provide new approaches to diagnosis and vaccine development.

Our own studies employ the blood stages of the parasite and cover three main areas: enzymes of importance in parasite metabolism; antigens of potential use in a subunit vaccine; and repetitive DNA as a probe able to distinguish genetically different isolates of P. falciparum and as a species-specific diagnostic tool in human and mosquito infections.

Red blood cells from rats were labelled with 51Cr by in vitro incubation with labelled sodium chromate. After re-injection of autologous labelled red cells, rats, each infected with 5000 N. brasiliensis larvae, and non-infected controls were placed in individual metabolism cages. Twenty-four hour samples of faeces and urine from both groups were collected throughout the course of the infection. From a knowledge of the specific radioactivity of host blood, it was possible to express the radioactivity found in the faeces and urine in terms of volume of whole blood. A burden of approximately 1000 adult worms caused a blood loss of about 100 μl every 24 h during the period day 4 to day 14 after infection. This gastro-intestinal haemorrhage could provide a vehicle whereby antibody gains access to the worm. No radioactivity was found in adult worms isolated from infected rats killed at 2-day intervals throughout the course of the infection. Adult N. brasiliensis did not ingest an appreciable quantity of host blood.

The structure of the ovarian tissue in juvenile Corynosoma semerme and C. strumosum from a fish paratenic host and in the cystacanth stage of Echinorhynchus gadi from an amphipod intermediate host was investigated by means of transmission electron microscopy. The species were obtained from hosts living in the Baltic Sea. The observations indicate that ovarian development was more advanced in cystacanths of E. gadi than in juveniles of C. semerme and C. strumosum. Free ovaries were present in E. gadi with an obvious supporting syncytium and surface microvilli. The biological significance of the different stages of ovarian development in these species is discussed briefly in relation to either reproductive strategies and host specificity in definitive hosts or to the attainment of infectivity by cystacanths in intermediate hosts.

Host specificity of a siphonostome copepod Ophiopsyllus reductus was confirmed by the results of an extensive survey of co-existing possible alternate host brittlestars. The parasite was found only on Ophiocomella ophiactoides. The ability to discriminate between potential hosts was tested experimentally. O. ophiactoides was always preferred and, in experiments with unrelated alternative hosts, the discrimination was absolute. When closely related species were the alternate host, discrimination was less complete. It is suggested that the discrimination is due to recognition of either tactile or chemical characteristics of the preferred host.

Viktorocara acholonui sp.nov. is described from a babbler, Alcippe brunnea, from Taiwan. It differs from V. charadrii Belopolskaja, 1959, and V. guschanscoi Leonov, 1958, in having a longer pharynx and in shape of tip of left spicule, and from V. tenuis (Maplestone, 1932) in having 6 rather than 10–13 pairs of preanal papillae.

Smetaleksenema gen.nov. is proposed for Skrjabinobronema pileati Smetanina et Alekseev, 1968, which becomes Smetaleksenema pileati (Smetanina et Alekseev, 1968), comb.nov. It differs from Ancyracanthopsis Diesing, 1861, in having serrated cephalic processes. The species is redescribed.

Ornithostrongylus vetterlingi sp.nov. is described from emerald doves, Chalcophaps indica, from Borneo and Palawan. It differs from all other species in the shape of the gubernaculum and in possessing a striated, common spicule sheath which binds the spicules tightly together.

Also reported and briefly discussed are: Viguiera dicrurusi Gupta, 1960; V. buckleyi (Yeh, 1954) Chabaud, 1957; Cyrnea (P.) excisiformis Yamaguti, 1935; C. (P.) leptoptera (Rudolphi, 1819) Chabaud, 1958; C. (C.) eurycerca Seurat, 1914; Physaloptera alata Rudolphi, 1819; Ornithostrongylus quadriradiatus (Stevenson, 1904) Travassos, 1914; O. travassosi Maplestone, 1932; Amidostomum skrjabini Boulenger, 1926; and Epomidiostomum anatinum Skrjabin, 1915.

We wish to acknowledge the field support by Dr D. S. Rabor, Department of Biology, Silliman University, Dumaguete City, Negros Oriental, Republic of the Philippines, and the technicians of the Parasitology Department of Naval Medical Research Unit No. 2 for general assistance in procurement and examination of hosts, and to Mr H. G. Deignan (deceased), U.S. National Museum, for identification of birds.

Initial work for this study was supported by funding under Public Law 480, section 104(c), by funds provided by the Bureau of Medicine and Surgery, Navy Department Work Unit MR 005.20-0098, by contract no. NR 103-690/N 0014-66-C0094, between the Office of Naval Research, Department of the Navy, and the Southwest Foundation for Research and Education, and research grant HE-5-P01-6M-13252-02 from National Institutes of Health, USPHS.

Final efforts were sponsored by Department of the Army, contract no. DADA17-68-C-8094.

The in vivo effects of the anthelmintics taenifugin, VÚFB 14170 and VÚFB 15269 on the tegument of Hymenolepis fraterna have been examined by SEM, TEM and cytochemistry. The drugs were given to H. fraterna-infected mice on the 14th day post-infection in a single oral dose of 150, 200 and 200 mg/kg, respectively. By 72 h post-treatment, the drug-induced pathomorphological changes in the tegument indicated that all three drugs had a significant effect. Changes were most pronounced on the brush border and in the intercellular material. On the apical surface, there was blebbing as well as accumulation of membrane fragments over the microthrix tips and erosion of the brush border. The intercellular material was changed in structure, showing increased electron density in some areas and oedema of the intercellular spaces in other areas. There were also fractures of the tegument of variable depth, sometimes reaching to the parenchyma. These results suggest altered tegumental integrity and, occasionally, complete disruption of the selective permeability barrier created by the normal tegument. This suggestion is further supported by the penetration of ruthenium red into some tegumental areas and its distribution into the intercellular spaces, down to the parenchyma. The intrategumental lysosomes also appeared to be significantly activated. There was evidence of autophagy in both distal cytoplasm and tegumental cells. Mature and gravid proglottides were more susceptible to drug damage than those in the anterior strobila and neck.

In a paper recently published in Parasitology (Baker, 1960), I referred to the description of trypanosomes from the fish Malapterurus electricus and Labeo macrostoma by Rodhain (1908). Most regrettably, I was unaware until after my paper was printed of the existence of a later publication by Rodhain (1942) in which these trypanosomes were named Trypanosoma malopteruri (sic.) and T. gandéi, respectively. Rodhain's descriptions are rather brief, and it is difficult to compare them with those of earlier authors, which are often also lacking in detail: however, in the light of present knowledge of the morphological variability of these large trypanosomes and their wide host-ranges (in the few cases in which these are known), there seems to be no sure ground for regarding T. malopteruri and T. gandéi as valid species: possibly both are synonyms of T. toddi Bouet (1909), if it be assumed that Bouet saw only the larger forms of a pleomorphic species.

Cyclin-dependent kinases (CDKs) have important roles in regulating key checkpoints between stages of the cell cycle. Their activity is tightly regulated through a variety of mechanisms, including through binding with cyclin proteins and the Cdc2/Cdc28 kinase subunit (CKS), and their phosphorylation at specific amino acids. Studies of the components involved in cell cycle control in parasitic protozoa are limited. Trichomonas vaginalis is the causative agent of trichomoniasis in humans and is therefore important in public health; however, some of the basic biological processes used by this organism have not been defined. Here, we characterized proteins potentially involved in cell cycle regulation in T. vaginalis. Three genes encoding protein kinases were identified in the T. vaginalis genome, and the corresponding recombinant proteins (TvCRK1, TvCRK2, TvCRK5) were studied. These proteins displayed similar sequence features to CDKs. Two genes encoding CKSs were also identified, and the corresponding recombinant proteins were found to interact with TvCRK1 and TvCRK2 by a yeast two-hybrid system. One putative cyclin B protein from T. vaginalis was found to bind to and activate the kinase activities of TvCRK1 and TvCRK5, but not TvCRK2. This work is the first characterization of proteins involved in cell cycle control in T. vaginalis.

Cell extracts of an entero-invasive protozoon of squirrel monkeys, Tritrichomonas mobilensis, contained relatively high proteolytic activity, measured on hide powder azure (HPA). Multiple proteinase forms, optimally active at pH 5–7, were detected by electrophoretic analysis in gelatin-containing polyacrylamide gels. Three major proteinase bands of apparent low molecular weights, Mr 18, 23 and 30 kDa, were seen on gels. Inhibition-activation studies suggest that only cysteine proteinases were involved in HPAase and gelatinolytic activities of T. mobilensis cell extracts.

The complete intracellular cycle of the Leishmania mexicana mexicana G. S. strain was quantified in human macrophages and in the mouse IC-21 macrophage line utilizing a culture system that allows the direct observation of individual intracellular parasites. A wide range of pre-replicative lag periods exists, implying that promastigotes may be in any phase of their DNA synthetic cycle when phagocytosed by the macrophage. Amastigotes replicated 2–3 times, after which the host cell died and liberated amastigotes that were taken up by other macrophages and continued to replicate. The mean amastigote population-doubling time in human macrophages (17.5 h) was not statistically different from promastigotes growing in axenic culture (16.4 h), but was nearly 2-fold less than amastigotes growing in mouse-derived IC-21 macrophages (33.7 h). These observations are markedly different from cover-glass culture assays of Leishmania-macrophage interactions and provide an unambiguous description of the intracellular cycle of Leishmania mexicana mexicana.