There is a great deal of empirical data and theoretical predictions on the patterns and processes of trematode behaviour, particularly in relation to host-finding activities by the free-living stag...

Trematode behaviours and the perceptual worlds of parasites

The tegument of the cercaria of Zoogonoides viviparus has been studied in detail using the scanning and transmission electron microscopes. The greatest part of the cercarial body is provided with long, recurved spines. The anterior end of the cercaria is extremely specialized. A circle of microvilli, about 5 µ long, is found around the mouth. Numerous sensory structures composed of a central cilium and nervous tissue penetrating the tegument are found throughout the body, but in large numbers on the anterior end near the mouth. Apical to the mouth the invaginated stylet and the openings of the penetration glands are found. At least three distinct types of cells connect with the syncytial tegument. One type is similar to tegumentary cells previously described from most adult trematodes. In addition, what appear to be two types of cystogenous cells are found. The secretory products of these cells are released into the tegument. The tegument covers the external surface as well as the pharynx and oes...

On the histochemistry and ultrastructure of the tegument and associated structures of the cercaria of Zoogonoides viviparus in the first intermediate host

IN THIS PAPER I propose to bring together significant facts already known to have some bearing on the mechanisms which govern or influence host compatibility or incompatibility during parasit ism, to add information based on my own recent research, and to present some speculations. From the broad viewpoint, host compatibility may be defined as the expression of the physical and physiological (including chemical) states of the host and parasite which enable the parasite to invade and carry out its life processes, includ ing perpetuation of the species. Incompatibi lity refers to those factors which completely or part ially prevent the establishment and normal development of the parasi te. Both of these are highl y complex phenomena influenced to one degree or another by a series of separate but commonly int errelated factors. As workin g models from which we can seek evidence to support or reject various working hypotheses, we have chosen to examine the relationship between molluscs and digenetic trematodes, since this category of association, unl ike a num ber of others, is an example of parasitism whether the definition of \"parasitism\" is couched in nutritional, pathological, ecological, or immunological terms. Molluscs, except in a very few unusual instances, serve as interm ediate hosts for the Digenea, but this fact does not render them less appropriate as exper imental tools. In fact, inasmuch as it is generally accepted that molluscs were the original hosts

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The compatibility and incompatibility concept as related to trematodes and molluscs.

Acid phosphatase activity was demonstrated in the intact blood nematodes, Dirofilaria immitis and Angiostrongylus cantonensis . Biochemical studies on acid phosphatase, using intact females and whole worm, body-wall and visceral homogenates were undertaken to clarify the characteristics and the distribution of the enzyme. In D. immitis , high acid phosphatase activity was observed at pH 3·8–5·8 and in A. cantonensis , at pH 4·5–6·0. Molybdate, fluoride, copper and zinc ions and L(+)-tartrate were effective inhibitors of the enzymes of both parasites while cobalt and magnesium ions and D(−)-tartrate had no noticeable effect on the activity. When the effect of substrate concentration on the phosphatase activity was studied, kinetic curves of Michaelis–Menten type were obtained with the 2 species of intact worms as well as their homogenates. The reproductive organs and body wall of D. immitis showed high total acid phosphatase activity. In A. cantonensis , the majority of the enzyme was localized in the body wall. The activity of intact A. cantonensis expressed as μg Pi/h/mg dry weight decreased with increase in mean worm weight. The characteristics of the acid phosphatase of the 2 nematodes are compared with those of other parasitic helminths and of acid phosphatase of mammalian origin. The localization of the phosphatase responsible for the hydrolysis of the external substrate has been discussed for D. immitis and A. cantonensis based on results of the kinetics and distribution of the enzyme.

Acid phosphatase activity demonstrated in the nematodes, Dirofilaria immitis and Angiostrongylus cantonensis with special reference to the characters and distribution.

Molecular variation in fasciolids and Paragonimus.

Biochemical studies on the non-specific phosphomonoesterases of Fasciola hepatica have shown the presence of acid phosphomonoesterase active at pH 4·6 and two forms of alkaline phosphomonoesterases active at pH 7·6 and pH 9·6 respectively. Histochemical studies have located acid phosphomonoesterase in the walls of the intestinal caeca and to a lesser extent in the tegument. Alkaline phosphomonoesterase was found to occur mainly in the excretory ducts and to a lesser degree in the uterine wall. Glycogen was mainly concentrated in the yolk glands, parenchyma, mature eggs and the non-muscular regions of both oral and ventral suckers.Dr A. J. Probert takes pleasure in recording the support of the British Council and the Indian University Grants Commission to enable him to study in India.

Biochemical and histochemical studies on the non-specific phosphomonoesterases of Fasciola gigantica Cobbold 1855.

The migration of cercaria x baylis (strigeida) within the molluscan intermediate host lymnaea stagnalis.

By means of serial sections of experimentally infected Eisenia foetida with Metastrongylus spp. The distribution of larvae within the host has been determined. The exact position in the host intestine at which larvae penetrate has been shown to be the crop. The preferred site for localization and development of the parasite has further been shown to be the lamellar sinuses of the calciferous glands, although larvae were recovered from the dorsal blood vessel, hearts and perienteric blood sinuses. The way in which larvae pass from the gut to their definitive positions in the host has been discussed and it is supposted that this is determined by the configuration of the blood system rather than by a predilection for an environment low in free carbon dioxide. The pathology of infection and the distribution of alkaline and acid phosphatases, lipases, non-specific esterases RNA, DNA and haemaglobin have been described. The distribution of phosphatases in the gut is suggested to be concerned in the uptake of nutrients. The presence of an active zone of enzyme activity in the subcuticular regions of the parasite has been shown and the significance of this discussed. The parasite has been shown to feed directly on host blood.

Morphological and histochemical studies on the larval stages of Metastrongylus spp. (lungworms of swine) in the earthworm intermediate host, Eisenia foetida, Savigny 1826

Allan J. Probert

Papers

Biochemical and histochemical studies on the non-specific phosphomonoesterases of Fasciola gigantica Cobbold 1855.

The migration of cercaria x baylis (strigeida) within the molluscan intermediate host lymnaea stagnalis.

Morphological and histochemical studies on the larval stages of Metastrongylus spp. (lungworms of swine) in the earthworm intermediate host, Eisenia foetida, Savigny 1826