Sex Genotype and Sex Phenotype Contribute to Growth Differences between Male and Female Channel Catfish

摘要

Channel catfish Ictalurus punctatus have an XX female-XY male genotypic system of sex determination, and male channel catfish grow faster than females. Through selective breeding and appropriately timed hormone administration, we have produced phenotypic male channel catfish with a YY sex genotype and female channel catfish with an XY or YY sex genotype. In this study, we evaluated the relative role of sex genotype and sex phenotype in regulating sexually dimorphic growth in this important aquaculture species. ten families of genotypic XY male fish were produced by matings of normal XX female fish with YY male fish, and females were produced by hormonal feminization of a subsample from each family. The growth rate and body composition of sibling males and females in ponds where the sexes were maintained together were compared with those in ponds where the sexes were maintained separately. Generally, phenotypic males had higher body weight (15.25% and 11.36% when the sexes were together or separated, respectively), standard length (3.28% and 2.24%, respectively), and condition factor (2.94 and 2.65, respectively), while phenotypic females had higher liposomatic index (7.11% and 13.69%, respectively) and dress-out percentage (0.91% and 1.06%, respectively). Statistical differences between the phenotypic sexes were not as consistent as observed in previous studies with normal males and females because growth and body composition differences were enhanced when the sexes were maintained together; however, monosex culture restrained these differences. These results demonstrate that sex genotype and sex phenotype both contribute to the male growth advantage in channel catfish and provide further evidence that monosex male culture would produce an economic gain of about 5% for the industry compared with conventional mixed-sex culture.