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To supply more documentary evidence for the effect of parasitic infection on activity of neurosecretory centres in the cerebral ganglia of the snail host, caudo-dorsal and light green cells of adult individuals of Lymnaea stagnalis naturally infected with digenean parthenites were subjected to karyometric analysis. In infected animals significant enlargement of nuclear volumes of both examined types of neurosecretory cells was ascertained. Mean nuclear volume of the light green cells in snails infected with Furcocercariae was significantly lower in comparison with the individuals infected with parthenites from groups Echinostomata and Xiphidiocercariae. In remaining cases differences in nuclear volumes among subpopulations distinguished on the ground of an infection factor were not statistically significant.
Studies upon behariour of snails in anthropogenically changed water environment. 1. Locomotor activity of lymnaea stagnalis (L), with regard to subpopulations infected with developmental stages of digeneans. The aim of the paper was to analyse the locomotor activity of snails, Lymnaea stagnalis, with regard to physico-chemical properties of water in an inhabited reservoir and parasitic infection. The material was collected in selected anthropogenic water environments situated in the Upper Silesian Industrial Region (sinkhole ponds, sand-and clay-excavations). The locomotor activity of each snail was analysed in laboratory conditions by designation of number of penetrated segments, marked in tanks filled with water originating from a given reservoir, during 15', with intervals of l'. It was observed the significant relationship between locomotor activity of examined snails and the water carbonaceous hardness (r = -0,812, at range of the independent variable 173.0-863.5 mg CaCO₃/dm³). Correlation coefficients with other physico-chemical parameters of water were close to zero. Locomotion of snails infected with developmental stages of digenetic trematodes was significantly lower comparing to non-infected individuals. Locomotor activity of these former ones was dependend more on degree of the digestive gland damage by the parasite than on the infection agent.
Accumulation of zinc in epithelial cells of the digestive gland tubules of the freshwater snail Lymnaea stagnalis after subacute intoxication with zinc acetate (strong increasing doses of the metal in short period of time) was histochemically examined using dithizone. Large zinc granules observed in medial and basal parts of calcium cells permitted to conclude that this metal is binded in cytoplasm mainly on granules built of calcium and magnesium phosphate. There were no smaller concentrations of zinc, that would be indicative for metal binding with cytoplasmatic metallothionein-like proteins. In calcium cells of the digestive gland tubules of snails infected with digenean larvae accumulation of zinc was stronger, that would be an aspect of compensatory reaction.
Acid and neutral lipids in epithelial cells building tubules of the digestive gland of snails naturally infected with digenean larvae were stained with nil blue sulphate. Strong decrease in number of phospholipids granules in secretory cells, as well as in calcium cells in the infected glands was observed. The larvae caused also decrease of number of neutral lipids in both types of cells, but these changes were much smaller and did not refer to small granules laying in top parts of the epithelial cells. Changes in number of lipids granules were limited only to the cells of tubules damaged by parasites.
The effect of exposure of juvenile individuals of Lymnaea stagnalis to infectious eggs of Opisthioglyphe ranae on dynamics of their growth was investigated under controlled conditions in laboratory. In infected snails enlargement of body weight and linear parameters of shell were observed. Any differences in shell shape, analysed on the base of regression of shell width towards to its height, were not ascertained in uninfected snails and those infected with parthenites of the trematode. The findings with this host-parasite system are discussed in relation to possible mechanisms of pathogenesis of somatic gigantism in other trematode-snail interactions.
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