Chromosome numbers, genome sizes, cell volumes and evolution of snake-head fish (family Channidae)

Chromosome number, C-value and cell volume studies were carried out on three species of the genus Channa , viz., C. punctatus, C. striatus and C. gachua . The chromosome number, karyotypic structure and DNA content per cell along with cell volume are reported and described. A series of chromosomal rearrangements are established in three different karyotypes along with polyploidy. Both pericentric inversion and Robertsonian fusion played a major role in chromosome rearrangements. The nuclear DNA content of these three species is within 19-29% of the present-day placental mammals, and is thus lower than the median amount for fishes in general and teleosts in particular. Their lower DNA content suggests that the three species of the family Channidae are highly specialized, and this is supported by their known morphologic, reproductive, behavioural and ecological characteristics.
The evolutionary significance of these chromosomal rearrangements, their origin and their mode of establishment are discussed. A probable phylogenetic model based on karyotype, C-value and chromosomal rearrangements of the genus is presented.