Natural occurrence of monoploids and polyploids in the Indian catfish, Heteropneustes fossilis

Abstract

Owing to the absence of well-defined sex chromosomes in fishes, polyploidy has spontaneously originated, perhaps repeatedly, and has been sustained in populations of diverse orders. In fact much has been written on this subject by Ohno. Expectedly, natural triploid populations have evolved in 8 genera representing 3 orders of fish; the viviparous Poeciliids (Poecilia, Poecilopsis), oviparous Cyprinids (Carassius; Misgurnus; Phoximus; Rutilus) and Athernids (Menidia). Viable hybrid unisexual triploids have also been recorded in Poecilia: (i) P. latipinna-2 mexicana, and (ii) P. latipinna-mexicana; Poecilopsis: (i) P. 2 monacha-lucida (ii) P. monacha-2 lucida, and (iii) P. monacha-viriosa-lucida; and Phoximus: (i) P. 2 eos-neogaeus, and (ii) P. eos-2 neogaeus. Likewise, naturally occurring tetraploids have been reported in Carassius auratus, the European Barbus sp., Misgurnus anguillicaudatus and Cobitis biwae. The frequency with which unusual base replacements, inactivating mutations can occur in the duplicated genes, and the workload for replication has perhaps minimized the abundance of tetraploid fish species.