Capoeta x Luciobarbus hybrids. Hybrids between species of Capoeta and Luciobarbus have been recorded in areas where both species occur together. These hybrids were known to early ichthyologists exploring West Asia and have been named as Barbus species. Hybrids are often difficult to distinguish in the field, especially if they are young. In several Capoeta and Luciobarbus, the shape of the mouth is quite variable, and hybrids may bridge the gap between the mouth and head shapes of Capoeta and Luciobarbus. All Luciobarbus, for which data is available, are tetraploid with 100 chromosomes, while all Capoeta are hexaploid with 150 chromosomes. If a tetraploid (n = 4) parent and a hexaploid (n = 6) parent hybridise, the offspring is pentaploid (n = 5) and is likely to be sterile, as all odd-numbered hybrids are. The occasional findings of mitochondrial bodies of Luciobarbus in Capoeta species demonstrate that there must be a way of hybridogenous introgression via these pentaploid hybrids. This implies that at least some hybrids must be able to produce even-chromosome eggs or sperm (n = 2 or 4). These eggs can develop and produce a new, even-chromosome-numbered hybrid, which can reproduce with the pure species and transfer the mitochondrial body of one species into the other. However, this is merely speculative; the only certainty is that it must function somehow. Further research is required to elucidate the process of introgressive hybridisation in uneven chromosome cyprinids. In areas where two Capoeta species co-occur, hybrids are also observed, which exhibit morphological intermediary characteristics between the parental species. In Capoeta, it is frequently observed that in pure fish, the mitochondrial body of a syntopic species is present. For instance, in the Orontes drainage, C. damascina with the mitochondrial body of C. barroisi and vice versa are frequently observed, while morphologically intermediate fish are notably scarce.

Published as part of Freyhof, Jörg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, GmbH, Berlin / Boston :De Gruyter on page 137, DOI: 10.1515/9783111677811, http://zenodo.org/record/17881367