Influence of the transmission of parasites from prey fishes on the composition of the parasite community of a predatory fish

Helminth parasites and diet of seven freshwater fishes (Lota lota and six common prey species) from the Bothnian Bay, Baltic Sea, were studied monthly or bimonthly during 1978. Twenty-one of the 32 parasites with complex life cycles were shared between Lota lota and its prey fishes and are thus transmissible from prey to predator. Gymnocephalus cernuus and L. lota had the greatest number of shared species (13). Larval and adult cestodes, nematodes, and acanthocephalans could re-establish in the predator, but only one adult trematode was capable of this transition. Infracommunity species diversity was highest in L. lota (eH′ = 3.54), which also had the most species (24), the highest mean number of species and individuals of a given species per fish (6.3 and 62, respectively), and the greatest number of worms in one fish (520). Variety of diet was key in determining exposure to parasite species. However, most specificity finally determined if a given parasite could establish and mature. No ecologically explicable suites of parasites were found in any fish species, except in a few cases where parasites used related intermediate hosts. However, the composition of these suites was not retained in the predator. Unlike in L. lota, important parasites of prey fishes were typically specialists.

Phosphoglucoseisomerases in the sporocyst of the trematode Schistosoma mansoni and its intermediate host Biomphalaria alexandrina (Pulmonata)

It has been found by use of electrophoresis that the hepatopancreas of the snail Biomphalaria alexandrina (Ehrenberg) contains one phosphoglucoseisomerase. Snails which have secondary sporocysts of the trematode Schistosoma mansoni contain an additional phosphoglucoseisomerase which is also found in the adult trematode. It is supposed that the secondary sporocysts are secreting phosphoglucoseisomerase into the hepatopancreas of the snail in order to increase the transformation of glycogen to simpler carbohydrates, in which form the parasite is able to absorb the carbohydrates necessary for metabolism.

On a new trematode Echinoparyphium bagulai sp.nov., (Echinostomatidae) from Anas poecilorhyncha

In November 1953, about one-half per cent of Lymnaea luteola taken from a pond in Alfred Park, Allahabad, were infected with an echinostome cercaria. The first collections of these cercariae were made by Dr Onkar Nath Srivastava, who was surveying cercarial infections in the snails and who kindly gave me the echinostome material. Additional material was obtained by numerous subsequent collections. After the cercaria was described it was possible to undertake a limited number of experiments in an attempt to discover other stages of the life cycle. It was found that Lymnaea luteola is both the first and the second intermediate host of a new species of Echninoparyphium. The adult of this new species, for which the name E. bagulai is proposed, matures in the intestine of the domestic duck, Anas poecilorhyncha. When this duck was experimentally infected with cercariae, the adult trematode was recovered from the intestine of this duck 21 days after its infection.

STUDIES ON THE HETEROPHYID TREMATODE APOPHALLUS VENUSTUS (RANSOM, 1920) IN CANADA: PART III. FURTHER HOSTS

Amia calva and Ictalurus punctatus are added to the list of carriers of the cysts of Apophallus venustus in the lower Ottawa Valley, and a probable human infection with the adult trematode is recorded.

Observations on Bilharziasis amongst the Egyptian Expeditionary Force

In 1851, Bilharz (1852) first discovered paired adult trematode worms originally named after him in the portal system of an Egyptian fellah. Subsequently, investigations of the deposits of ova in excreta were made, but numerous attempts by Cobbold, Sonsino, Lortet and Vialleton (1894) and others, to unravel the life history of the parasite, failed. Looss (1896), appreciating that the digenetic trematodes must necessarily pass through a molluscan intermediary, dissected many species of snails collected from the fresh-water canals around Cairo. He failed to find the cercariae of bilharzia, and discarded the hypothesis of an intermediate molluscan host. As, however, the miracidium of Schistosomum haematobium contained germinal cells within its body cavity, it must, naturally, he argued, have been destined to produce sporocysts at some stage of its life cycle. In view of this, Looss evolved the hypothesis that man acted simultaneously as the intermediary, as well as the definitive host of this parasite.