KARYOTYPIC VARIATION WITHIN THE GENUS LEIOPELMA (AMPHIBIA: ANURA)

Abstract

The chromosome complements of four specimens of the anatomically primitive frog Leiopelma hochstetteri are described from cultured cells and squashes. The basic karyotype in all cases consists of 22 chromosomes, 12 of which are acrocentric. Supernumerary chromosomes are either absent or variable in number, but appear to be constant in the somatic cells of any one individual. The limited evidence available suggests that the supernumerary chromosomes do not pair during male meiosis.The karotype of L. archeyi is described for the first time. Only the smallest pair of the total complement of 18 chromosomes is acrocentric. Supernumeraries are absent.The distribution and probable relationships of the species of Leiopelma are discussed. The karyotypes of Leiopelma and the North American ascaphid frog Ascaphus truei are compared, with particular reference to the relationship of the supernumerary chromosomes of Leiopelma and the microchromosomes of Ascaphus.

Triploidy in Hochstetter's frog,Leiopelma hochstetteri, from New Zealand

“…1). As noted by Stephenson et al (1972), there was a prominent secondary constriction on chromosome 7 in all specimens. The 3 copies of this chromosome were easily recognised in the triploid.…”

“…The diploid karyotypes of the specimens examined did not differ appreciably from the results presented by Stephenson et al (1972). One supernumerary chromosome was found in each of the 4 diploid females examined but the male specimen had no supernumeraries in its karyotype.…”

“…Mitotic metaphase spreads were obtained from squashes of gut epithelial cells, using the methods described by Stephenson et al (1972) and those of Kezer & Sessions (1979). Slides prepared from this material were examined at the University of Oregon with a Zeiss photo microscope, using phase contrast optics.…”

“…L. hochstetteri lives along the margins of streams in scattered localities on the North Island of New Zealand and lays its eggs in damp seepages near the streams. This species has 2n=22 chromosomes and varying numbers of supernumerary chromosomes (Stephenson et al 1972). L. archeyi and L. hamiltoni have extremely restricted ranges and both have 2n=18 chromosomes; they lack supernumerary chromosomes (Stephenson et al 1974).…”

“…This species has 2n=22 chromosomes and varying numbers of supernumerary chromosomes (Stephenson et al 1972). L. archeyi and L. hamiltoni have extremely restricted ranges and both have 2n=18 chromosomes; they lack supernumerary chromosomes (Stephenson et al 1974). Supernumerary chromosomes are rare in anurans, and only 4 species are known to possess them (Jones & Rees 1982).…”