Relaxation of selective constraints on avian mitochondrial DNA following the degeneration of flight ability

The evolution of flight is the most important feature of birds, and this ability has helped them become one of the most successful groups of vertebrates. However, some species have independently lost their ability to fly. The degeneration of flight abilit

Larval metamorphosis and morphological characteristic analysis of triploid shrimp Fenneropenaeus chinensis (Osbeck, 1765)

Both MI and MII triploids were successfully produced by heat shock in Chinese shrimp Fenneropenaeus chinensis. The inducing conditions for MI and MII triploids were optimized. The highest inducing rate obtained for MI triploids reached more than 90%, and that for MII triploids reached nearly 100% at the nauplius stage as evaluated using flow cytometry. Comparisons of survival rates at larval stages between triploids and diploids or diploids experiencing treatment and diploids without treatment were performed. At larval stage from nauplii to postlarvae, heat shocks lowered survival at larval stages even if the ploidy was not changed. Ploidy did not affect shrimp larvae survival, and no significant difference was found in the survival of shrimp larvae between MI and MII triploids. Highly significant differences were observed in the morphology of triploids and diploids, and no apparent difference was found in the morphology of MI and MII triploids at the grow-out stages. Discriminating formulae for triploid and diploid shrimp at grow-out stage were developed and could be used to distinguish triploids from diploids based on morphological parameters. MI and MII triploids of shrimp have the potential to be used in aquaculture.

Comparative growth performances of diploid and triploid Chinese shrimp Fenneropenaeus chinensis (Osbeck, 1765) under different salinities

This study aimed at evaluating the ploidy effects on growth performances of Chinese shrimp (Fenneropenaeus chinensis Osbeck, 1765) reared in different salinities under laboratory conditions. In the acute salinity experiment, there was no difference (P > 0.05) in tolerance observed in triploid and diploid shrimp due to abrupt salinity changes. The lethal salinity for 50% of the individuals in 96 h at 23-25 degrees C was about 2 g L-1 in both triploids and diploids. While for the chronic salinity experiment, statistical analyses confirmed that the differences in growth performances including the specific growth rate (SGR), the feeding rate (FR), feed conversion efficiency (FCE) and intermoult period (IP) between triploid and diploid were related to salinity. Diploid shrimp reared in 20 g L-1 exhibited highest SGR (P < 0.05), while triploids performed well in 20 and 30 g L-1 salinities (P < 0.05). Based on the survival and growth data, the optimal salinity for the culture of diploid F. chinensis should be 20 g L-1 and for triploids it should be between 20 and 30 g L-1.