New karyotypic data for Asian rodents (Rodentia, Muridae) with the first report of B‐chromosomes in the genus Mus

Abstract

Karyotypes of 18 rodent species collected in various localities in Thailand were analysed as part of an epidemiological survey of the region using conventional cytogenetic techniques. The aim was to re-assess the reliability of karyotype-based diagnoses of Thai rodents using an updated taxonomic framework. The species examined include Menetes berdmorei (Sciuridae), Mus caroli, Mus cervicolor and Mus cookii, Hapalomys delacouri, Chiropodomys gliroides, as well as several representatives of most of the lineages of the Rattini tribe, that is Rattus exulans, Rattus losea, Rattus tanezumi, Leopoldamys edwardsi, Leopoldamys neilli, Maxomys surifer, Niviventer fulvescens, Berylmys berdmorei, Berylmys bowersi, Bandicota indica and Bandicota savilei (Muridae). The first descriptions of G-and/or C-banding karyotypes are provided for several of these, that is, B. savilei, L. edwardsi, M. surifer, B. berdmorei, B. bowersi, N. fulvescens and H. delacouri. Although largely in agreement with available data, our findings on chromosome morphology differ slightly from those published for L. edwardsi, M. surifer, B. savilei and the two Berylmys species, B. berdmorei and B. bowersi. In addition, we document the novel finding of B-chromosomes in the genera Berylmys, Bandicota and the emblematic Mus. Importantly, few species-specific chromosomal characteristic could be identified within most of the genera investigated in our study and, in contrast to previous claims, the usefulness of karyotypes for diagnosing these Asian murid species appears to be limited.

Karyotypic Evolution of <i>Hapalomys</i> Inferred from Chromosome Painting: A Detailed Characterization Contributing New Insights into the Ancestral Murinae Karyotype

“…1 a). In the original description the species was regarded as having a 2n = 48 karyotype with a metacentric or submetacentric autosomal complement and easily identifiable sex chromosomes (the metacentric X and the acrocentric Y were regarded as the largest and the smallest elements in the karyotype) [Badenhorst et al, 2009]. However, our painting data showed that 1 chromosome of pair 23 in the original description represents the unfused homolog of the XY 1 Y 2 translocation ( fig.…”

“…This contrasts with the conventional view that Hapalomys falls within the Micromys division and is part of the tribe Rattini [Musser and Carleton, 2005;Lecompte et al, 2008], making it a pivotal species in resolving rodent phylogenetic relationships. Although G-and C-band data have been reported for H. delacouri [Badenhorst et al, 2009], …”

“…1 ) that mirrors the situation in an unrelated species, Bandicota savilei (Rodentia, Muridae, Rattini) . The FISH analysis permitted a revision of the original karyotypic description of H. delacouri [Badenhorst et al, 2009] through the identification of a sex-autosome translocation and a B chromosome ( fig. 1 a).…”

“…comm.]. The chromosomes were analysed by trypsin G-banding and arranged following Badenhorst et al [2009]. Nucleolar organizer regions (NORs) were detected by silver staining [Goodpasture and Bloom, 1975] using DAPI-banded metaphase spreads.…”

Progress on research on rodents and rodent-borne zoonoses in South-east Asia

“…Asian rats are known to host numerous pathogens but are still difficult to identify to species level using morphological or karyotypic criteria (Badenhorst et al 2009;Chaval et al 2010). Moreover, reliable species identification is hampered by our imprecise knowledge of South-east Asian rat taxonomy, the lack of clear species limits within some genera (e.g.…”