Karyotypes and cytogenetic diversity of the genus Cobitis (Pisces, Cobitidae) in Poland: a review. Cytogenetic evidence for a hybrid origin of some Cobitis triploids.

This work summarized the results of comparative chromosomal study of Cobitis fish from 13 locations in Poland. At least two distinct species C. taenia and C. elongatoides were cytogenetically recognized. The populations of C. taenia were detected in only three lakes located in northern Poland. One hybrid diploid, four triploid and four tetraploid forms were recognized among the samples. These hybrid forms or biotypes of Cobitis could not be distinguished by external characteristics. Based on the species-specific chromosome markers such as NORs, CMA3-positive and C-bands, it is hypothesized that C. taenia, C. elongatoides, and one or two other species have taken part in the origin of polyploids. Two different hybrid diploid-polyploid Cobitis complexes were distinguished. One was composed of C. taenia, two triploid hybrid forms and two tetraploids. The other complex included C. taenia and C. elongatoides, which have taken part in the origin of coexisting hybrid forms: diploid hybrid C. taenia-elongatoides, four different triploid and two tetraploid biotypes. The results obtained indicate the hypothetical mode of origin of some polyploid Cobitis forms.