Entomologica Romanica Vol. 17 / 2012
2012
Entomologica romanica 17: 5-11, 2012 ISSN 1224-2594 / article no.: ER17201201 Terrestrial isopods in the diet of two amphibian species (Epidalea viridis and Pelobates syriacus) from Dobruja, Romania Severus-D. Covaciu-Marcov, Sára Ferenți, Alfred-Ș. Cicort-Lucaciu & István Sas-Kovács Summary: Two amphibian species from Dobruja (Epidalea viridis and Pelobates syriacus) consumed five terrestrial isopod species (Trachelipus rathkii, Porcellionides pruinosus, Porcellio laevis, Armadillidium vulgare and Armadillidium versicolor), beside other invertebrates. The most frequent isopod species in frogs' food was A. vulgare. The isopods consumed by amphibians are either common species in Romania, or characteristic to the southern area of the country. Therefore, amphibians consumed the common isopods in the populated area. Even though the region from which the frogs were captured is uniform, between the feeding of the two amphibian species were some differences. P syriacus constantly has fed on large preys, while E. viridis frequently consumed small sized preys too, such as ants. It seems that these difference, also determined the differences between the consumption of inorganic elements and vegetal remains between the two species. Probably, searching for certain prey types, E. viridis had a larger foraging territory, while P syriacus, species that has not manifested any trophic selectivity, presents a smaller foraging territory, since that territory had a satisfactory quantitative trophic offer. Key words: invertebrates, amphibians’diet, foraging territory, isopods Introduction Even though recent studies referring to amphibians' feeding are extremely numerous (e.g. Solé et al. 2009, Lima et al. 2010, Paunovic et al. 2010, Qiqek 2011, Polymeni et al. 2011, Cald art et al. 2012), there are few data concerning certain groups of invertebrates of which they feed (e.g. Holzinger et al. 1996, Tomescu et al. 2010). Terrestrial isopods can be used as indicators of some particularities of amphibians feeding, offering valuable information on the foraging territory of some species (see in: Tomescu et al. 2010). These results are extremely important in terms of conservation, as almost all the amphibians from Romania are protected by law (O.U.G. 57 / 2007). However, to our best knowledge, in Romania the only study regarding the isopods from amphibians’ food was conducted in north-western region of the country (Tomescu et al. 2010). The fact was expectable, since most of the amphibians' food composition studies from Romania were conducted in that region (e.g. Kovács et al. 2007, Covaciu-Marcov et al. 2010a,b, Cicort-Lucaciu et al. 2011a, b, Sas et al. 2009). However, such studies were made in other regions of Romania, too (e.g. Ghiurca and Zaharia 2005, Dobre et al. 2007, Bogdan et al. 2012), including Dobruja (e.g. Covaciu-Marcov et al. 2010c). Unlike north-western Romania, in Dobruja are present other amphibian species with conservation value, located there at the northern limit of their distribution range, such as Pelobates syriacus (Cogalniceanu et al. 2000). Therefore, P syriacus is a species adapted to dryness, as well as Epidalea viridis, even if it is widespread in Romania (Cogalniceanu et al. 2000), being one of the most common species of amphibians from Dobruja (Covaciu-Marcov et al. 2006). Thus, we decided to analyze the isopods consumed by these two amphibian species in a semi-natural habitat from Dobruja, at the same time referring to their general feeding. Materials and methods The fieldwork was conducted in 15 April 2012. E. viridis and P syriacus individuals were captured by hand, at the beginning of the night, both species being nocturnal (Cogalniceanu et al. 2000). The study area was situated near Ceamurlia de Jos locality, from Dobruja. The frogs were capture near the village railway station and along the approximately 2 km long road which leads from the railway station to the village. The region is dry, covered with rare, grassy vegetation, with a typical aspect of central Dobrujan Plateau. However, a few kilometers away there is the limit of the Razelm - Sinoe lagoon complex. The amphibians were captured between 23.00 and 00.00 PM, either from the illuminated surroundings of the railway station, or at the headlights of a car on the