Banded karyotypes of Allactaga williamsi from Central Anatolia

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1 Research Article Turk J Zool 34 (2010) TÜBİTAK doi: /zoo Banded karyotypes of Allactaga williamsi from Central Anatolia Atilla ARSLAN 1, *, Jan ZIMA 2 1 Department of Biology, Faculty of Science, Selçuk University, Konya - TURKEY 2 Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno - CZECH REPUBLIC Received: Abstract: A chromosomal study of 2 populations of Allactaga williamsi from Konya province in Central Anatolia, Turkey, was performed. The diploid number of 48 chromosomes was found in all of the 5 specimens examined. All of the chromosomes except the Y were biarmed and could be identified by unique G-banding patterns. The C-banding analysis revealed a considerable amount of constitutive heterochromatin in all chromosomes. The C-band positive regions were distributed mainly in centromeric areas, whereas the Y chromosome stained uniformly and C-negatively. The active NORs were localized in 2 pairs of small metacentric and submetacentric autosomes. The species of the genus Allactaga are apparently conservative in their karyotypic structure. Key words: Jerboa, comparative cytogenetics, G- and C-banding, AgNOR staining Orta Anadolu daki Allactaga williamsi nin bantlı karyotipleri Özet: Orta Anadolu daki Konya bölgesinden 2 Allactaga williamsi populasyonunun kromozomal çalışması yapıldı. Çalışılan 5 örneğin tamamında diploid kromozom sayısı 48 olarak bulundu. Y hariç kromozomların tamamı iki kolluydu ve G-bantlı örnekler ile de tanımlandı. C-bantlama analizi konstitutif heterokromatinin bütün kromozomlarda önemli miktarda olduğunu gösterdi. C-bantlı pozitif bölgeler başlıca sentromerik bölgelerde dağılmıştı, ancak Y kromozom tek tip boyandı ve C-negatifti. Aktif NOR lar küçük 2 çift metasentrik ve submetasentrik otozomlarda lokalize olmuşlardır. Allactaga cinsini türleri karyotip yapıları içinde açıkça korunuyor. Anahtar sözcükler: Çöl faresi, karşılaştırmalı sitogenetik, G- ve C-bantlama, Ag-NOR boyama Introduction Allactaga williamsi Thomas, 1897 was described on the basis of a single specimen from Lake Van, and its distribution range extends through Turkey, Caucasia, Iran, and Afghanistan (Çolak et al., 1994; Wilson and Reeder, 2005). In Turkey, Ellerman (1948), Os born (1964), and Kral and Benli (1979) recorded the species from Erzurum and Central Anatolia (Konya, Amasya, Kayseri, and Nevşehir). The conventionally stained karyotype of A. williamsi was described by Çolak et al. (1997b) from Elazığ, Malatya, and Niğde, in Turkey. However, information on differentially stained chromosomes and the detailed structure of the karyotype is still lacking for * [email protected] 533

2 Banded karyotypes of Allactaga williamsi from Central Anatolia this species. The aim of this study was to perform a chromosomal banding analysis of the karyotype of A. williamsi with the use of G- and C-banding and Ag-NOR staining to facilitate further comparative cytogenetic studies among jerboas. Materials and methods The animals studied (5 males) were collected from Konya Province (Gölyazı, Cihanbeyli, N, E, and Çumra, N, E) (Figure 1). Karyotype preparations were obtained from the bone marrow of animals treated with colchicine (Ford and Hamerton, 1956). After preparation of chromosome slides, conventional Giemsa-staining was carried out. G-banding was performed following the technique determined by Seabright (1971). Constitutive heterochromatin and nucleolus organizer regions (NORs) were detected in individual autosomal and sex chromosome pairs via C-banding (Sumner, 1972) and Ag-NOR staining (Howell and Black, 1980), respectively. From each specimen, slides were prepared, and at least 20 well-spread metaphase plates were analyzed. Chromosome morphologies were determined after calculating centromeric indexes. Standard voucher specimens (skins and skulls) were deposited in the Department of Biology, Faculty of Science, Selçuk University, Konya, Turkey. Results The karyotype of A. williamsi consists of 48 chromosomes, including 6 metacentric pairs (numbers 1-6 in Figure 2), 12 submetacentric pairs (numbers 7-18), and 5 subtelocentric pairs (numbers 19-23) of autosomes (NFa = 92). The largest metacentric autosomal pair was distinctly bigger than the other 5 pairs of the same morphological group. The largest submetacentric autosomal pair was the distinctly biggest element of the complement. Secondary constrictions were observed in the long arms of autosomal pair numbers 4 and 7. The X chromosome was medium-sized and submetacentric, and the Y chromosome was small and acrocentric (NF = 96). All of the autosomes and both of the sex chromosomes could be reliably identified on the basis of their unique G-banding patterns (Figure 3). The C-banded karyotype of A. williamsi is illustrated in Figure 4. All of the autosomes possessed distinct C-positive bands. The C-positive regions were usually extensive and included relatively large pericentromeric areas, except for pair numbers 3, 4, 14, 16, and 18, which revealed only weak centromeric C-positive bands. The size of the C-positive region on pair number 12 was heteromorphic. The X chromosome had a centromeric C-positive band and the Y chromosome appeared to be uniformly and C- negatively stained N 40 Gölyazı Çumra km km Figure 1. Collection localities of Allactaga williamsi in Konya. Cihanbeyli (Gölyazı), 3 (38 33 N, E) and Çumra, 2 (37 35 N, E). 534

3 A. ARSLAN, J. ZIMA Figure 2. Metaphase spread and karyotype of Allactaga williamsi from Konya, Turkey. Arrows indicate the position of secondary constrictions. Figure 3. Metaphase spread and G-banded karyotype of Allactaga williamsi from Konya, Turkey. By using silver-nitrate staining, NORs were localized in the secondary constrictions in the long arms of metacentric pair number 4 and submetacentric pair number 17. All of the observed NORs were homomorphic and medium-sized (Figures 2 and 5). The number of active NORs ranged from 2 to 4 per cell with an average of 3.3 (n = 20). Discussion Karyotypes of the specimens studied were compared with those reported for Allactaga williamsi, A. euphratica, A. tetradactyla, A. elater, A. major, A. sibirica, and A. jaculus (Vorontsov and Malygina, 1973; Zima and Kral, 1984; Çolak et al., 1997a, 1997b; Çolak and Yiğit, 1998; Shahin and Ata, 2001, 2004; 535

4 Banded karyotypes of Allactaga williamsi from Central Anatolia Figure 4. Metaphase spread and C-banded karyotype of Allactaga williamsi from Konya, Turkey. Figure 5. Silver-stained metaphase spread and karyotype of Allactaga williamsi from Konya, Turkey. Arrows indicate the position of active Ag-NORs. Ata and Shahin, 2006; Sözen et al., 2008). It seems that the genus is chromosomally rather conservative as no karyotypic difference can be detected among the species studied so far. Most of the published data concern conventionally stained chromosomes only, and it is possible that detailed comparisons of differentially stained karyotypes will reveal some variation. According to Shahin and Ata (2004) and Ata and Shahin (2006), only a part of the chromosomes of A. tetradactyla showed distinct C- positive bands, and dark C-staining was not observed in certain autosomes and the X chromosome. In relation to our data in A. williamsi, this difference may indicate a possible variation in the amount and distribution of C-heterochromatin among the species of the genus Allactaga. A more detailed molecular analysis using cytochrome b sequence mapping technology will be needed to determine the patterns of genome variation or conservation in the genus Allactaga. 536

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