Meiotic differentiation in two allopatric population groups of the tetraploid frog Odontophrynus americanus from Argentina (Amphibia: Anura: Cycloramphidae)

LANZONE C.; BALDO D.; ROSSET S.

HERPETOLOGICAL JOURNAL

Año: 2008 vol. 18 p. 213 - 222

0268-0130

The Odontophrynus americanus species complex presents a wide distribution in South America and is conformed by diploid and tetraploid cryptic species. We studied the meiotic prophase stages of two allopatric tetraploid population groups, a southeastern and a northwestern, from Argentina. These two allopatric population groups showed a bouquet polarization in cigotene and pachytene, and in the latter stage a complete synapsis of quadrivalents and bivalents was observed. In diakinesis the frequency of different elements per cell was counted and compared with two teorethical distributions for an autotetraploid organism. Both model tests show the same overall result. The frequency of quadrivalents does not depart significatively for the models in southeastern populations, and must be considered autotetraploid of recent origin. However, northwestern populations have a significatively reduced number of multivalents, which can be explained by diploidization or allotetraploidy. The reduction of quadrivalents is relatively low when compared with one of the models. Additionally, different chiasmata frequencies occur between bivalents and quadrivalents in both population groups. The presence of extra-chromosomes detected in southeastern populations and the mitotic and meiotic irregularities reported from others populations, not observed in the studied here, confirm a high cytological variability among populations of the tetraploid Odontophrynus americanus, which can be adscrited to polypoidy.