Polyploidy in the Australian leptodactylid frog genus Neobatrachus

Abstract

Karyotypic analysis of six species of the Australian leptodactylid frog genus Neobatrachus showed that N. pictus, N. centralis, N. pelobatoides and N. wilsmorei are diploid (2n = 24) while N. sudelli and N. sutor are tetraploid (4n = 48). Polyploidy has not been reported previously among Australian anurans. Idiograms of the six species indicate that they are similar to the other Australian leptodactylids so far discribed. DNA values of the tetraploids are approximately double the values for diploids. Tetraploid nuclear and cell sizes are greater compared with diploids but total body size shows no increase. At diakinesis in primary spermatocytes of tetraploids, mainly tetravalents together with a few bivalents are present. Silver straining of metaphase spreads clearly demonstrates the location of NORs at the secondary constrictions and their frequent association in the tetraploid N. sutor. Nucleolar number in interphase nuclei provides a reliable guide for distinguishing tetraploid from diploid frogs in the absence of chromosome analysis and can be determined for both living and preserved specimens. The possible origins and relationships of the tetraploid species are discussed.

A comparison of the karyotype, constitutive heterochromatin, and nucleolar organizer regions of the new tetraploid species <i>Xenopus epitropicalis </i>Fischberg and Picard with those of <i>Xenopus tropicalis </i>Gray (Anura, Pipidae)

“…This is in contrast to reports con cerning other polyploid anurans (B e^ak et al" 1966, 1967. 1970Bogart, 1967; Wassirm a n , 1970; Bogari and T andy, 1976; Mahony and Robinson, 1980), in which multivalents were the rule.…”

Polyploid Incidence and Evolution

“…In plants, polyploidy is sometimes, but not always, associated with larger overall size (114). In vertebrates, polyploidy tends to have little to no effect on body size (35,76,104), but it tends to increase size in invertebrates (12, pp. 266, 300-301).…”

Nucleolar organiser region (NOR) location in karyotypes of Australian ground frogs (family Myobatrachidae)

“…Metacrinia Parker, 1940 Live sl~ecimens were transported to the laboratory and processed as soon as possible after capture. Mitotic spreads were obtained from duodenal epithelium using a technique described by Mahony and Robinson (1980). At least five karyotypes were prepared and measured for each species usually from several specimens.…”

“…However, Morescalchi and Ingram (1978) used the limited karyotypic data to point to some generic affinities. For a summary of the limited previous work on the chromosomes of myobatrachid frogs see Mahony and Robinson (1980). The present study was undertaken (a) to establish the extent of variation in NOR location in a large number of genera and species of Myobatrachidae, and (b) to determine whether NOR location has any taxonomic and phylogenetic value, particularly at the generic level, in a family where the current state of nomenclature and phylogenetic relationships are distinctly unstable (Tyler, 1979).…”