Nematode infestation in Rana arvalis Nilsson, 1842: the role of age and geographic location
E. A. Malkova1, A. V. Burakova1, I. A. Kshnyasev1, V. L. Vershinin1,2
1Institute of Plant and Animal Ecology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
2Ural Federal University, Yekaterinburg, Russia
Keywords: Rana arvalis, skeletochronology, nematodes, endoparasites, climate
Abstract
In the studied populations of Rana arvalis Nilsson, 1842 (ranging from the western macroslope of the Middle Urals to the Ishim Plain), ten parasite species were identified, with the nematodes Oswaldocruzia filiformis (Goeze, 1782) and Rhabdias bufonis (Schrank, 1788) being dominant. A two-component (hurdle) model-combining binomial regression (infection probability) and gamma regression (infestation intensity) -provided the best biological and statistical fit for nematode infestation patterns. Both infection probability and intensity increased with host age, peaking at 3-4 years: each unit increase in log2-transformed age [log2(Age+1)] raised the odds of infestation 6.2-fold (95 % CI: 4.9-7.8) and intensity 1.4-fold (1.2-1.5). Intensity also increased 2.1-fold (1.8-2.5) per additional nematode species. Geographic trends revealed latitudinal and longitudinal variability: infestation odds decreased 2.1-fold (1.5-2.7) per degree northward, while intensity increased 1.14-fold (1.1-1.2) per degree eastward. Neither host morph (striata/maculata) nor sex significantly influenced nematode infestation parameters.
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