Entomologica Romanica Vol. 17 / 2012
2012
case of a P. syriacus individual. This low number was due to the consumption of an approximately 10 cm long earthworm. All the preys consumed by these two species were terrestrial. Beside animal preys, both amphibian species consumed vegetal fragments, shed skin and inorganic elements. Discussion The identified isopods in the diet of both amphibian species from Ceamurlia de Jos are in generally common species, related to southern and drier areas of the country, fact that is consistent with the aspect and position of the region. Thereby, terrestrial isopods consumed by the two species of amphibians differ much from those consumed by the amphibians studied in the past in north-western Romania (Tomescu et al. 2010). In north-western Romania amphibians fed on species related to wetlands, forests, even mountain areas (see in: Tomescu et al. 2010). On the contrary, at Ceamurlia de Jos, species, with such ecological preferences, lacked from frogs' diet. This fact is a consequence of the differences between the two regions. Thus, in general, in north-western Romania are present terrestrial isopod assemblages related to wetlands (e.g. Ferenti et al. 2012, Ferenti and Dimancea 2012), while in Dobruja are present numerous southern species, related to drier areas (see in: Radu 1983,1985, Giurginca and Curcic 2003). The differences are also valid regarding amphibians, even P syriacus being a species found in Romania at the northern limit of its distribution range (Cogalniceanu et al. 2000). Thus, amphibians consume isopods present in the habitats and regions they populate. These results confirm that isopods from amphibians' food could serve as instruments for measuring the habitat quality and ecological requirements of the frogs (see in: Tomescu et al. 2010). Most species of terrestrial isopods consumed by amphibians from Ceamurlia de Jos were recorded before in Dobruja (see in: Radu 1983,1985, Tabacaru and Boghean 1989, Tomescu 1992, Giurginca and Curcic 2003). All isopods identified in amphibians' diet are large-sized species, with high mobility, not being identified small-sized species with low mobility, even though according to literature data, these are abundant in Dobruja (Radu 1983, 1985, Giurginca and Curcic 2003). Similarly, in amphibians' food from north-western Romania large and mobile terrestrial isopods were also identified (Tomescu et al. 2010). The consumption of large-sized species was explained by their higher abundance (Tomescu et al. 2010). At the same time, the absence of small-sized species may represent also a consequence of their generally endogeic life (see in: Radu 1983), the studied region being at the same time too arid to be favourable for isopods with such ecological requirements. T. rathkii is considered a common species in Romania, including Dobruja (see in: Giurginca and Curcic 2003), therefore its presence in amphibians' food is not something unusual. P pruinosus is a xerophilous, Mediterranean species, being considered invasive in Romania (Radu 1985). Due to its origin, it is favoured by the climate from Dobruja, where it was frequently reported (Tabacaru and Boghean 1989, Giurginca and Curcic 2003). Thus, the presence of many individuals of P pruinosus in the food of amphibians is not surprising. P laevis is a southern species, being rarely encountered in Romania, in Dobruja being recorded only in the southern parts (Giurginca and Curcic 2003). Therefore, this species' presence in amphibians' food increases the knowledge about its distribution in Dobruja. Probably, at Ceamurlia de Jos P laevis is favoured by the railway station's buildings, as it was found in other cases near anthropogenic places (Vandel 1968), including in localities (Giurginca 2006). This fact may also explain the occurrence of P laevis only in the diet of only one amphibian species, due to its presence in a small part of the amphibians hunting territory. So, P laevis was encountered only by frogs that foraged around the buildings. A. vulgare is a synanthropic isopod considered very common in Romania (Radu 1985). Along with T. rathkii. they are the only species consumed by the amphibians from Ceamurlia de Jos as well as by those from north-western Romania (Tomescu et al. 2010). Probably, this species also took advantage of the railway station buildings due to its synanthropic character. A. vulgare was consumed in large quantities by both amphibian species, being the most frequent species in the stomach contents of the frogs which consumed isopods. Even though, P pruinosus had the highest percentage in the stomach content of P. syriacus, the frequency of A. vulgare was much higher. The fact indicates a higher accessibility of A. vulgare for amphibians, probably the species being more evenly distributed in the foraging territory of the frogs. The preys with high frequency are more accessible and evenly distributed in the foraging territory, being more important for the amphibians than those consumed in high percentage, but by a low number of frogs, fact mentioned in other cases, too (see in: Dobre et al. 2007, Kovács et al. 2010). It seems that A. versicolor was not mentioned before in Dobruja (Giurginca and Curcic 2003), although, it is well represented in other regions of Romania (Radu 1985, Tomescu et al. 1995, 2000, 2005, 2011), being also mentioned in northern Bulgaria (Radu 1985). Along with A. vulgare and A. versicolor, E. viridis has consumed another species belonging to Armadillidium genus, which could not be identified, due to the low number of males and the fact that they were in advanced digestion stage. Even so, it is possible that those isopods belong to A. traiani, a species encountered not far away, on Popina Island (Giurginca and Curcic 2003). Judging by consumed isopods, it seems that 8