Inheritance and Variation of Genome Size in Half-Sib Families of Hybrid Catfishes

Abstract

We used high-resolution flow cytometry to study variation in genome size within half-sibling families of hybrid catfishes produced from parents representing three genera of the family lctaluridae. Genome size of hybrid offspring was exactly intermediate to the genome sizes of parental stocks, indicating that nuclear DNA segregates as a function of haploid DNA content and is stable within intergeneric hybrids. Thus, measuring genome size could provide a useful method for identifying hybrids within natural populations of fish or other organisms. Within-group variation in genome size was less than 2.5% for all groups studied, including outbred parental stocks. These values may represent the minimal level of genome size variation detectable within populations by analysis of interphase nuclei. The variation in genome size of ictalurid catfishes is small compared to variation observed in other vertebrates, and may be due to evolutionary conservatism within the catfish genome or to the appearance in other taxa of mechanisms that generate variation in DNA mass.