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The excretion of P-PO₄ and N-NH₄ by snails (Lymnaea (Lymnaea) stagnalis, Lymnaea (Radix) auricularia and Planorbarius corneus) was measured in laboratory experiments. For L. (L.) stagnalis the release of these elements from decomposing animals and their faecal material were also determined. Amounts of nutrients excreted by the snails studied varied greatly in the ranges <1 to 70 μg P-PO₄ and <2 to over 200 μg N-NH₄ per individual. These amounts were very much related to the sizes of snails. The phosphorus and nitrogen contained in the tissues of L. (L.) stagnalis are released to the water very rapidly due to the rapid decomposition that the bodies of snails undergo. The release of phosphorus from freshly produced faecal matter is considerable - even greater than the excretion by live snails (expressed per unit weight). However, the limited mass of faeces produced as compared with the body weight of an snail, ensures that this still accounts for only 3% of daily excretion of phosphorus from the body of a live snail.
We have proved highly significant differences in glucose concentration and activity of alpha-amylase in haemolymph of two growth classes of Planorbarius corneus with width of shell smaller and equal or greater than 20 mm, respectively. Both these parameters were higher and were characterized by greater range of individual variability in snails with smaller width of shell. Any differences in levels of total protein and haemoglobin in haemolymph of these animals, in comparison with adult individuals, were not observed. Effect of infection of the pulmonary cavity of investigated snails with Chaetogaster limnaei limnaei on the examined parameters was not ascertained.
A total of eight species of furcocercous cercariae of four families (Strigeidae, Diplostomidae, Schistosomatidae and Sanguinicolidae), were found in 2005 in Lake Konnevesi in Central Finland in four snail species (Valvata macrostoma, Lymnaea stagnalis, Bathyomphalus contortus and Planorbarius corneus). Australapatemon burti (Miller, 1923), Australapatemon sp., Cotylurus brevis Dubois et Rausch, 1950, Cercaria spinulosa Ginetsinskaya, 1959 and Sanguinicola sp. are new species records for Finland. Ichthyocotylurus variegatus (Creplin, 1825) and Bilharziella polonica (Kowalewski, 1895) were first recorded as cercariae in Finland. The most common cercariae were A. burti (prevalence 13.3%) and Diplostomum pseudospathaceum Niewiadomska, 1984 (10.0%). Our study represents the first host record of Valvata macrostoma for larval stages of Australapatemon sp. and Sanguinicola sp.
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