The origin of the brown frogs with 2n=24 chromosomes

Abstract

Late replication and C-banding analyses of somatic metaphase chromosomes were attempted on three species of brown frogs with 2n = 26 chromosomes (Rana japonica, R. tsushimensis and R. temporaria), and three with 2n = 24 chromosomes (R. ornativentris, R. dybowskii and R. chensinensis), which are distributed in the Palearctic region. The late replication banding patterns were highly conserved in these species. Four chromosome inversions were demonstrated in R. ornativentris, two in R. dybowskii and two in R. tsushimensis. From a detailed comparison of late replication and C-banding patterns between the 2n = 26 and the 2n --24 species, it was found that an end-to-end fusion of two small chromosomes (nos 11 and 13) in an ancestral 2n = 26 species may have produced the medium-sized no. 6 chromosome of the 2n = 24 species. Key words. Brown frogs; 2n = 24; 2n = 26; late replication band; C-band; an end-to-end fusion.

Cytogenetic analysis of four species of Pseudis (Anura, Hylidae), with the description of ZZ/ZW sex chromosomes in P. tocantins

“…The presence of NORs on the long arms of chromosomes 7 is also common to all karyotypes, except for P. cardosoi, which differs from the other species by having 2n = 28 chromosomes and an NOR located on the long arms of pair 5, which is probably homologous to chromosome 7 of the other species (see discussion in Busin et al 2001). Although various authors have proposed a trend towards a reduction in chromosome number during the evolution of amphibian karyotypes (Beçak et al 1970;Bogart 1973;Miura et al 1995), the occurrence of karyotypes with 2n = 24 chromosomes in all species of the genus except for P. cardosoi supports the hypothesis raised by Busin et al (2001) that karyotypes with 2n = 28 chromosomes represent an apomorphic condition in Pseudis.…”

Cytogenetic analysis of four central Amazonian species of Colostethus (Anura - Dendrobatidae) with a diploid complement of 22 chromosomes

“…Some species belonging to different dendrobatid genera have telocentric chromosomes which suggests centric fusion and fission as possible mechanisms for changes in the chromosomal number in this family, as also found in other anuran groups (B ogart and H edges 1995; M iura et al 1995; B usin et al 2001). According to B ogart (1991), other chromosomal rearrangements, such as translocations and inversions, are probably involved in the karyotypic evolution of Colostethus , since even within the 2n=24 group some species have no telocentric chromosomes.…”

Intrageneric karyotypic divergence inScythrophrysand new insights into the relationship withParatelmatobius(Anura, Leptodactylidae)

“…In the specimens from Rancho Queimado, the variation was restricted to the size of the NORs and of two C-bands. In anurans, such intrapopulational variation in NOR size (Schmid, 1978a(Schmid, , b, 1980a(Schmid, , b, 1982Silva et aL., 1999) and heterochromatic bands (Schmid, 1978a(Schmid, , b, 1980aKing, 1980;Schmid et aL., 1990Schmid et aL., , 1993Miura et aL., 1995) has been extensively described. On the other hand, the specimens from Säo Bento do Sul showed variation in pair 5 and in the occurrence of an additional NOR.…”