Karyotype diversity suggests that Laonastes aenigmamus (Laotian rock rat) (Rodentia, Diatomyidae) is a multi-specific genus

Karyotype analysis of Quasipaaspinosa David, 1875 (Anura, Dicroglossidae) with conventional cytogenetic techniques

The current study analyzed the chromosomal karyotype of Quasipaaspinosa David, 1875 from Hunan Province, China. The karyotype, C-banding, BrdU-banding pattern were characterized using direct preparation of bone-marrow cells and hemocyte cultures. The findings indicated that Q.spinosa was a diploid species (2n = 26) that lacked heteromorphic chromosomes and secondary constrictions. C-banding analysis revealed an abundance of positive signals in the centromere regions, while the BrdU-banding pattern showed three phases in both male and female, occurring consistently and in chronological sequence during S-phase. Notably, there was no asynchronous replication in the late phase. This study enhanced our understanding of the karyotypic structure of Q.spinosa by conventional cytogenetic techniques, thus providing essential scientific insights into the cytogenetics of Q.spinosa.

Karyotypic polymorphism of Crocidura tanakae (Eulipotyphla: Soricidae) and revision of the karyotype of C. attenuata in mainland China

Conventional karyotypes of Crocidura tanakae and C. attenuata collected from mainland China were examined by bone marrow and cell culture methods along with identification to species using molecular data. In contrast to C. tanakae from Taiwan, populations from mainland China were karyotypically polymorphic, varying in diploid number (2n) from 24 to 40 and fundamental number (FN) from 45 to 56. Autosomes are composed of 6–20 metacentric or submetacentric chromosomes, 0–8 subtelocentric chromosomes, and 0–24 telocentric chromosomes. These polymorphic karyotypes indicate the presence of two geographically separated races. The ancestral karyotype of C. tanakae potentially is the same as currently found on Taiwan: 2n = 40 and FN = 56. In contrast to C. tanakae, C. attenuata had a uniform karyotype (2n = 40, FN = 54) in mainland China, suggesting that previously reported karyotypic polymorphism in this species was an error due to the morphological crypsis between C. tanakae and C. attenuata in mainland China. The intricate karyotypic polymorphism of C. tanakae may be indicative of this species undergoing speciation.

High BrdU Sensitivity of Passeriformes Chromosomes: Conservation of BrdU-Sensitive Fragile Sites on Their Z Chromosomes during Evolution

Amongst 15 bird species, representative of 7 orders, recurrent breakages evocating the presence of fragile sites were detected in the chromosomes of the 5 species belonging to Passeriformes. These breaks appeared when 5-bromodeoxyuridine (BrdU) was added to the cell culture medium at a dose inefficient for inducing chromosome structure alterations in other birds and mammals. They involved, similarly in male and female, 3 loci on the Z chromosome of 3 Turdus species (Turdidae). Labeling by BrdU antibody confirmed the correlation between BrdU incorporation into DNA and breakage, especially around and in the sites of breakage. Thus, 3 BrdU-sensitive fragile sites were present in the Z chromosomes of these birds. Three fragile sites were also detected at different locations in the Z chromosomes of the European robin (Erithacus rubecula, Muscicapidae), suggesting that a structural rearrangement occurred during the evolution of Turdidae and Muscicapidae. Chromosome banding confirmed this interpretation. Finally, in the more distantly related species Parus major (Paridae), the almost acrocentric Z chromosome displayed a single BrdU-sensitive fragile site in its short arm, and the W appeared to be pulverized by BrdU incorporation. Although it cannot be excluded that the BrdU-sensitive fragile sites may be involved in rearrangements, their conservation in many species, and possibly all Passeriformes, provides evidence that they do not constitute a pejorative character during evolution.