Starch gel electrophoresis and morphometric characters were used to assess the geographical variation between 14 populations of the moor frog, Rana arvalis, from northern and southern areas in Central Europe. Six of the 13 screened allozyme loci were polymorphic (95% criterion). No fixed difierences in allele composition between the two regions were found. Some of the alleles were region specific. Genetic variability as measured by expected heterozygosity (He) and number of alleles per locus was significantly lower in the southern samples than in northern ones (He=0.104 and He=0.156, alleles/locus = 1.6 and 1.8 respectively). This is interpreted as a consequence of the difierent past history of these two groups during the Pleistocene. Population subdivision, as measured by FST, was substantial (0.124 and 0.078 for the southern and northern group, respectively); 59.9% of the between-locality variation is attributed to this division into two geographical groups. Isolation-bydistance was detected by significant negative correlation between the estimate of gene flow (log M) and log (geographical distance) only for the southern population groups. This indicates that the northern populations have recently recolonized their contemporary distribution area. The mean genetic distance between the northern and southern group of populations was DN = 0.062. Despite the relatively low genetic distance between them, the two population groups form two distinct clusters in the maximum likelihood (ML) tree. Discriminant analysis on 11 size adjusted body measurements showed considerable overlap between populations from difierent geographical areas. An isolated Romanian Reci population which genetically belongs to the southern group of populations was morphologically situated in an intermediate position between northern and other southern populations.

The objective of our study was to bring data upon the feeding of Rana lessonae, Rana arvalis from Reci region, Covasna County. We watched at the trophic spectrum of this two Rana species the variation depending on species, sex, habitat and diurnal activity. The feeding of moor frogs is more intense in twilight period. The largest diversity of preys was presented in the stomach contents of Rana lessonae samples captured from the pool. The females both of the two Rana species eat a greatest variety of preys vis a vis the males. Only Rana lessonae captured from the permanent pool present in stomach contents a relatively high number of aquatic preys.

The objectives of the current study were to  identify, in detail, the distribution of the largest moor frog populations from the Ier Valley  region and to assess the zones that represent important habitats and present measures for  their protection. Our study was conducted from March to October during the years 2001-2003. We identified 49 populations of Rana arvalis in the Ier Valley area. Most of these populations can be considered distinct, isolated from each other, apart from a few exceptions. This fact increases their regional chance of extinction. The Rana arvalis populations in the studied area occupy very different habitats. Only a few of these habitats can be considered natural biotopes. As a result of intense dry out of the swamps in the Ier Valley area, the populations of Rana arvalis had reduced in atypical smaller sized habitats, which  had a limitating effect on the size of these populations. Small numbers of moor frogs were found in most sites surveyed (less then 6 specimens / site / visit) in the region. We were able to calculate quantitative population assessments for five populations. The largest population was found near Andrid, with 675 ±57 adult specimens, making this one of the largest known population of Rana arvalis in Romania. The second significant population was estimated to be 354 ±25 individuals and it was located near Resighea. The other populations’ sizes were estimated at fewer than 200 adults. We consider the protection of the large breeding populations of Rana arvalis in the Ier Valley area to be a priority, by managing both the breeding and foraging habitats. The potential for the biggest moor frog populations to be part of a single infrastructure is discussed.

The moor frog (Rana arvalis) inhabits the largest territory of all Eurasian true frogs (Ranidae), and its east-west extension spans more than 7200 km, from northern France to beyond Lake Baikal. Within this area, the moor frog shows pronounced morphological and autecological (aquatic and terrestrial) variation, and at least in southeastern Europe a large amount of genetic variation. Nevertheless, no geographic subspecies can be delineated except the partly disputed  R. a. arvalis and  R. a. wolterstorffi. The latter inhabits a small area in the Pannonian region, whereas the former covers the reminder of the distribution range. The genetic-taxonomic status of marginal populations in the Balkans (Slovenia, Croatia) and the Ukraine remains as yet unresolved. A special feature of the moor frog is the purple or blue colouration of males during the breeding season, whose origin as well as function is as yet unknown. In northern Scandinavia, as well as some southern populations, this colouration is missing or only observed in some years. Suitable habitats for the moor frog are very diverse, and encompass moor edges, heath ponds, riverine forests, meadows and pastures, and even dry pine forests. Regional habitat specialisations are noted towards the margins of the distribution area, whereas the moor frog is rather a generalist in core areas. Habitat specialisation in the densely populated western border of its distribution constitute a major threat, as only unsuitable areas remain following habitat destruction. Rana arvalis is therefore in part highly endangered or at risk of extinction in France and southwest Germany, and sustainable and comprehensive conservation programmes are thus urgently necessary. Large-scale agricultural extensification measures and the creation of new breeding sites are key towards establishing connectivity between remaining populations and a restauration of their habitats. Additionally, further research into the speciesí conservation biology is necessary.

Influence of changing illuminance on the growth of fish juveniles and grass frog tadpoles was investigated. The maximum growth rate of all the species is observed under conditions of illuminance oscillations about certain values. For the fish growth, the regimes with 12- and 24-hour oscillations are the best. In the optimal varying regimes, the lower lethal oxygen level declines. Change of the darkness (0 lx) to bright light decreases the growth rate of fishes. Similar results are obtained in experiments with grass frog larvae