Chromosome and C-heterochromatin polymorphisms in the Italian newt, Triturus italicus

Abstract

A combined chromosome and C-heterochromatin polymorphism in pair 12 in the complement of the newt species, T. italicus is described. The C-heterochromatin polymorphism is presumably due to a loss in the proximal C-band, whereas the chromosomal polymorphism has its origin in two different independent pericentric inversions both including the centromere and the proximal C-band of chromosome 12. The double-inversion polymorphism has a wide distribution over the range and follows a clear bipolarity between a northern area where the karyotype is homomorphic for the standard type of pair 12 (ST/ST) and an opposite area where the ST type is completely replaced by variant M1 and M2 metacentric chromosomes 12. Various karyophylogenies are possible, but the simplest and the most probable presumes an ancestral karyotype of ST/ST and a mechanism of gradual replacement of the heterobrachial chromosome ST by two independent pericentric inversions. The present data are discussed in relation to existing theories on karyological evolution of Urodeles and the functional significance of telocentric chromosomes suggested by Sessions et al. (1982).

Molecular cytogenetics of the ribosomal (18S + 28S and 5S) DNA loci in primitive and advanced urodele amphibians

“…The only 5 s site variation reported here is related to a polymorphism of chromosome 12 occurring in the species T. italicus, which is thought to originate from pericentric inversions (Bucci-Innocenti et al 1983). Our data agree with this interpretation and show that the chromosome region involved in the rearrangement carries the 5 s rDNA locus.…”

“…1 A and 2B). Different karyomorphs of pair 12 have been described in T italicus, presumably originating from two independent pericentric inversions both including the centromere and the proximal C-band (Bucci-Innocenti et al 1983). In individuals homomorphic for the standard type of pair 12 ( S T E T ) , the 5 s sequences are located on the long arm of chromosome 12, at the pericentic C-band level (Fig.…”

A comparative study of mitotic and meiotic chromosomes of the Montandon's newt,Triturus montandoni (Urodela: Salamandridae) from Poland and Rumania

“…Reduction or addition of heterochromatin is an important phenomenon in the evolution of the Tritutus genome (Macgregor & Sessions, 1986;Macgregor, Sessions & Arntzen, 1990) and was also observed as an intraspecific polymorphism in Triturus italicus, T. alpestris and T. helveticus (Ragghianti, Bucci-Innocenti & Mancino, 1980;Bucci-Innocenti, Ragghianti & Mancino 1983a;Schmid, Olert & Klett, 1979). The reduction of size of a heterochromatic block on one of the arms of chromosome 3 of T. montandoni might be another example of such a polymorphism.…”

An integrative analysis of phylogenetic relationships among newts of the genus Triturus (family Salamandridae), using comparative biochemistry, cytogenetics and reproductive interactions

“…Although Triturus species have long been used in comparative biological studies, uncertainties still exist concerning phylogenetic relationships within the genus. Nine species and a number of subspecies were recognized by Thorn (1968), but more recently, twelve species have been recognized (Frost, 1985) on the basis of karyological and hybridization studies by Bucci-Innocenti et al (1983a) supported by an analysis of mitochondrial DNA (Wallis and Arntzen, 1989). Three subgenera have been recognized on osteological grounds (Bolkay, 1928;Thorn, 1968): one of large newts (Neotriton) including T. carnifx, T. cristatus, T. dobrogicus, T. karelini and T. marmoratus; one of small newts (Palaeotriton) including T. boscai, T. helveticus, T. italicus, T. montandoni, T. vulgaris and also T. vittatus; and a taxon (Mesotriton) including only T.…”