In C. marulius and C. marulioides, the NORs were located at the telomeric position of the short arm of acrocentric chromosomes corresponds to those observed in many of the Channa species (Sobita and Bhagirath 2006, Khakhong et al. 2014, Tanomtong et al. 2014). The two pairs of NORs-bearing chromosomes in these two species are different from the majority of fishes which have only one pair of NORs on the chromosome.