DISTRIBUTIONAL , MORPHOLOGICAL AND KARYOTYPIC CONTRIBUTIONS FOR THE EURASIAN WATER VOLE , ARVICOLA AMPHIBIUS ( LINNAEUS , 1758 ) ( RODENTIA : MAMMALIA ) , FROM TURKEY

The present study was focused on both the new distributional records and karyological data for Arvicola amphibius from the European part of Turkey. The karyotype of the Eurasian water vole was investigated by examining its metaphase chromosomes. The diploid number of chromosomes (2n), the fundamental number of chromosomal arms (FN) and the number of autosomal arms (FNa) were found to be 36, 64 and 60, respectively, for one female individual from a single locality in the European part of Turkey. It was determined that A. amphibius has 2n = 36 chromosomes, consisting of seven metacentric, three submetacentric, three subtelocentric and four acrocentric chromosome pairs. The X chromosome was a large submetacentric. The present study confirmed the previous results with regard to 2n. However, comparison of our findings with those of other authors indicates that there are karyotypic differences among the chromosomes. These differences were related to the morphology of chromosomes. Additionally, we reported external and skull measurements and new distributional records from six localities for the Turkish water vole. The measurements presented in this study conform to those of samples examined by other authors.

Rodents exhibit exceedingly high variations in their chromosome numbers and/or chromosome morphologies.This is a noteworthy peculiarity of the rodents.Among the species of the subfamily Arvicolinae, diploid numbers vary from 17 to 62 (O'Brien et al., 2006).The diploid number of the Eurasian water vole, A. amphibius, is also within this range.The karyotype of the Eurasian water vole A. amphibius was reported to be 2n=36 from Sweden, Switzerland, (former) Czechoslovakia, (former) Yugoslavia, Bulgaria, Caucasus, Spain, Austria and Romania (see Zima and Kral, 1984), and by Özkurt et al. (1999) from the Asian part of Turkey and Gözcelioğlu et al. (2006) from the European part of Turkey.
In this study, we aimed to confirm the karyology of A. amphibius from the European part of Turkey and to report external and skull measurements and new distributional localities from Turkey.

MATERIALS AND METHODS
A total of eight individuals of A. amphibius were randomly collected and observed from six ecologically different localities in Turkey (Fig. 1).Specimens were caught with mouse-like traps.Morphologically, these samples were identified in accordance with Kryštufek and Vohralik (2005).The measurements (mm) of skull for each individual were measured, following Harrison (1972), Özkurt et al. (1999), and Kryštufek and Vohralik (2005), with digital calipers to the nearest 0.01 mm.
Of the individuals collected, one female individual of A. amphibius from Kırıkköy, Lüleburgaz-Kırklareli (41 o 27' N, 27 o 14' E) located in the European part of Turkey (Fig. 1), known as Thrace, was analyzed karyologically.Standard flame-dried chromosome preparations were made directly from the bone marrow of the colchicine-treated animal (Ford and Hamerton, 1956).The cells were observed and photographed in a light microscope.The chromosome nomenclature for the centromeric position on the chromosomes follows Levan et al. (1964): metacentric (m), submetacentric (sm), subtelocentric (st) and acrocentric (a).
The skulls, skins and karyotype slides, are deposited at the Department of Biology, Faculty of Sciences, Erciyes University in Kayseri.Sugöze, Ardahan (1).The habitat of A. amphibius is showed in Fig. 2.

New distributional records of
The external and skull measurements of the examined individuals of A. amphibius from Turkey are shown in Table 1.Tail length is 63-87% of the head and body length, with an average value of 71%.The zygomatic breadth of the skull is 57-63% of condylobasal length of skull, with an average value of 59%.

DISCUSSION
The Eurasian water vole, A. amphibius, belongs to the family Cricetidae and subfamily Arvicolinae, and is widely distributed in the Palaearctic region (Wilson and Reeder, 2005;Batsaikhan et al., 2008).Despite its wide distribution in the Palaearctic, the Eurasian water vole is not common to the whole of Turkey (Kryštufek and Vohralik, 2005;Yiğit et al., 2006).According to Fig. 134 reported in Kryštufek and Vohralik (2005), the Turkish localities recorded for A. amphibius are not only relatively few but also remarkably scattered.Yiğit et al. (2006) also noted a similar distributional map to that of Kryštufek and Vohralik (2005).In this study, we contributed to the distributional map of A. amphibius in Turkey, recording newly six localities.The external and skull measurements (Table 1) from eight individuals conform to those of samples examined by Harrison (1972), Özkurt et al. (1999), and Kryštufek and Vohralik (2005).
In the water vole, the most common diploid number is 2n=36.However, the karyotype containing 37 chromosomes (2n=37), which has trisomy of the smallest autosome, was also reported from Sweden.In this species, the NFa is quite different, varying from 60 to 68.While NFa = 68 was reported from Sweden, Switzerland, (former) Czechoslovakia, (former) Yugoslavia, Bulgaria, Caucasus, Spain and Austria, NFa=60 was described in (former) Yugoslavia, Romania and Caucasus (see Zima and Kral, 1984).According to the karyological studies performed by Özkurt et al. (1999) and Gözcelioğlu et al. (2006) on A. amphibius in Turkey, it seems that 2n = 36 in the water vole, A. amphibius, is common.Despite the similarity of diploid number in A. amphibius from Turkey, there are some differences in chromosome morphology of A. amphibius (Table 2).Özkurt et al. (1999) have reported 2n=36, NF=64 and NFa=60 for A. amphibius (former A. terrestris) from Kırşehir in the Asian part of Turkey.According to Özkurt et al. (1999), the karyotype of population in Kırşehir is composed of nine pairs of metacentrics, four pairs of submetacentrics and four pairs of acrocentrics, and the X chromosome was a medium-sized  Gözcelioğlu et al. (2006) consisted of seven pairs of metacentrics, six pairs of submetacentrics and four pairs of acrocentrics, and the X chromosome was a medium-sized submetacentric.
In conclusion, in this study we did not encounter a trisomy of the autosomes in the karyotype from the European part of Turkey.For Turkish water voles, the karyotypes reported here and by Özkurt et al. (1999), andGözcelioğlu et al. (2006) may be representative of the karyological forms of A. amphibius in the European and Asian parts of Turkey and, in another opinion, depended on either the classification system used by each author or the inter-individual variation in how chromosomal measurements were made.Additionally, we assumed that the new records reported here provide a considerable contribution to the distributional map of A. amphibius in Turkey.

Table 1 .
External and skull measurements in eight samples of Arvicola amphibius from Turkey (Codes are indicated in Fig. 1) (*The individual karyotyped).