Comparative Analysis of Genetic Variability of mtDNA Sequences in Platichthys stellatus, Kareius bicoloratus and Their Hybrid (P. stellatus♀×K. bicoloratus♂)

Abstract:

Platichthys stellatus and Kareius bicoloratus are two common Pleuronectidae species that are highly valuable in the aquaculture industry. P. stellatus is endowed with high meat content and delicious taste while K. bicoloratus is highly resistant to diseases. Characteristics of their hybrids, however, were rarely reported. In this study, we explored the genetic variability of mtDNA sequences of P.stellatus, K.bicoloratus and their hybrid (P.stellatus♀×K.bicoloratus♂), using 24 P. stellatus, 24 K. bicoloratus and 40 hybrids as samples. We found that that the content of A+T base pairs was higher than that of the C+G base pairs in all 3 groups, and that the content of A+T base pairs in the hybrids was the same as in P. stellatus. The analysis of mtDNA Cytb gene and COI fragments suggested that the genetic distances between K. bicoloratus and P. stellatus were 0.085 and 0.045 respectively, and that the genetic distances between the hybrids and K.bicoloratus were 0.076 and 0.045 separately. Moreover, there was a very small differentiation (0.009) between the hybrids and P. stellatus based on the mtDNA Cytb sequence analysis, and there was no genetic differentiation between the 2 groups based on the mtDNA COI gene sequence analysis. The neighbor-joining (NJ) phylogeny trees constructed with the Kimura 2-parameter model showed that P. stellatus and the hybrid could be clustered into one branch, while K.bicoloratus belonged to another branch. In the NJ phylogenetic tree based on gene COI, the big branch including F1 hybrid and P. stellatus could be further divided into two small branches. One was P. stellatus and F1 hybrid with the left eyes, and the other was the F1 hybrid with the right eyes. These data strongly suggested that characteristics of the hybrid of P.stellatus and K.bicoloratus (P.stellatus♀ × K.bicoloratus♂) were maternally inherited. This study provided helpful information for the future research on the hybridization of the two species.