Half-smooth tongue sole (Cynoglossus semilaevis) is an important aquaculture flatfish in China. Cytogenetic analysis has revealed that its sex determination system is female heterogametic (ZZ/ZW). The W chromosome is morphologically larger and has been considered evolutionarily younger than any other chromosome in the set. However, the genetic origin and evolution process of this neo-chromosome remains unclear. In this study, 2 tandem arrays of rRNA genes were chosen to address this question.
The tongue sole, Cynoglossus semilaevis (Cynoglossidae), is one of the most economically important fishery resources in Korea. This study presents a preliminary investigation of the future viability of the complete aquaculture of tongue sole in Korea. Specifically, possible differences in genetic variability between wild populations of tongue sole from Korea and hatchery-produced populations of tongue sole from China were assessed using multiplex assays with 12 polymorphic nuclear microsatellite DNA loci. High levels of polymorphism were observed between the 2 populations.
Major histocompatibility complex (MHC) genes play an important role in the immune response of vertebrates. Allelic polymorphism and evolutionary mechanism of MHC genes have been investigated in many mammals, but much less is known in teleosts. We examined the polymorphism, gene duplication and balancing selection of the MHC class II DAB gene of the half-smooth tongue sole (Cynoglossus semilaevis); 23 alleles were found in this species. Gene duplication manifested as three to six distinct sequences at each domain in the same individuals.