Calodium (Capillaria) Hepaticum (Nematoda, Capillariidae) in insular small rodent populations

The data on the distribution of the nematode Calodium hepaticum (Bancroft 1893) Moravec 1982 (syn.: Capillaria hepatica, Hepaticola hepatica) on the islands of Kizhi Archipelago are reported (N 62°00'; E 35°12'). Samples were collected on 18 islands and the mainland part of the Kizhi skerries region in the period from August 2005 till 2014. The method of partial helminthological dissection was applied to 346 specimens of rodents belonging to two species – the bank vole Myodes glareolus Schreber 1780 (301 spm.) and the field vole Microtus agrestis Linnaeus 1761 (45 spm.). The prevalence and the abundance index of nematode were 16.6% and 1.1 in M. glareolus and 11.1%; 0.3 in M. agrestis, respectively. The highest prevalence and abundance of C. hepaticum were detected in mature voles. No sex-related differences were found. C. hepaticum was present in 12 of 19 sampling sites. On the islands where the sample number (host individuals) was over 15, the highest prevalence and abundance values were 57% and 5.8 spm., respectively. Significant positive coefficients of correlation (Spearman’s and Pearson’s ones) between nematode numbers and characteristics of the island were found in the pair «Prevalence – degree of isolation» (0.48 and 0.49). Single-factor analysis of variance showed that the size of the island had some effect on the nematode invasion prevalence and abundance. However, no significant regression relationship between the prevalence and abundance of nematodes and characteristics of an island was revealed by multivariate regression analysis (multiple regression): the coefficient of determination of the regression equation R2