Comparative analysis of the helminth fauna of Natrix natrix and Natrix tessellata (Reptilia, Colubridae) in the Samarskaya Luka National Park (Russia)

Abstract

The article presents the comparative analysis of the helminth fauna of the grass snake Natrix natrix and the dice snake Natrix tessellata, studied on four locations in the Samarskaya Luka National Park in 1996‒2011. We found that the parasite species diversity is higher in Natrix natrix. The helminth composition of Natrix tessellata was represented by a slightly depleted parasite fauna of Natrix natrix. Eighteen helminth species were found in Natrix natrix and 14 species were found in Natrix tessellata. Thirteen parasite species were scored in both studied species. Natrix natrix and N. tessellata inhabite similar habitats and have an average similarity degree of helminth composition. On the one hand, the revealed differences between the helminth fauna of Natrix natrix and N. tessellata are explained by the dietary preferences of the snake species. On the other hand, it is explained by the peculiarities of snakes' micro-habitats. The helminth fauna of Natrix natrix indicated their feeding mainly on tailless amphibians and by the fact that both snakes inhabit semi-aquatic locations in shallow water. The helminth composition of Natrix tessellata was caused by the consumption of fish and semi-aquatic inhabitation of this snake. The invasion of both reptiles by helminth species, scored in both studied snakess, varied on different locations. On some locations, Natrix tessellata was much more infected with parasitic worms. On other locations, Natrix natrix was more infected. This can be explained by the population size of intermediate hosts of the parasites on different locations, which were food objects of the reptiles. Natrix natrix was higher infected with trematodes. We found that Natrix tessellata was higher infected by the cestode Ophiotaenia europaea and the nematode Rhabdias fuscovenosa. The obtained parasitological data confirmed the partial trophic and spatial niche overlap of the two sympatric reptile species. The analysis of the helminth fauna of Natrix natrix and N. tessellata showed that there is a slight competition of reptiles for prey objects on locations studied in the Samarskaya Luka National Park.

Keywords

• colubrid snake
• dice snake
• grass snake
• helminth
• parasites