Stability of genome size among stocks of the channel catfish

Abstract

Nuclear DNA content of erythrocytes from male and female channel catfish ( Ictalurus punctatus) was determined by flow cytometry. Fourteen stocks of catfish were studied ( n=115), including domesticated and wild fish, fish from sex-reversed populations and those produced by gynogenesis. Mean DNA content was 1.977±0.010 (SD) pg DNA per cell, and mean within-stock variation was 1.28%. The stocks had an average difference of 0.19% from the species mean; no significant differences in DNA content were detected among the stocks or between males and females. The intraspecific variation among the channel catfish stocks examined is lower than that reported for other fish species. This may reflect artificial stabilization of genome size by human intervention, or alternatively, evolutionary conservatism within the genome of the channel catfish.