Effects of inbreeding on growth and survival rates, and immune responses of ridgetail white prawn Exopalaemon carinicauda against the infection of Vibrio parahaemolyticus

Abstract

Inbreeding could lead to a decrease in genetic variation within a population and subsequent depression of performance traits. The purpose of this study was to investigate the effects of inbreeding on the growth-related traits, immune responses, antioxidant status and the acute hepatopancreatic necrosis disease (AHPND) resistant capacity of ridgetail white prawn (Exopalaemon carinicauda) using a new inbred line named EC5. The results demonstrated that the genetic polymorphisms of EST-SSR markers decreased with an increase in artificial inbreeding, and there was less growth traits and a lower survival rate among inbred populations than the control population. Inbreeding effects on the immune responses and antioxidant status were studied in experimental full-sibling inbred populations of E. carinicauda at five levels of inbreeding coefficient (F = 0.785, F = 0.816, F = 0.859, F = 0.886, F = 0.908) under controlled laboratory conditions. Inbreeding affected the total haemocyte count, antibacterial activity and phenoloxidase (PO) activity, and the haemocyanin (HEM) concentration decreased after the ninth generation. Antioxidant status showed a similar pattern: superoxide dismutase (SOD) and catalase (CAT) activity in the cell-free haemolymph decreased. The effects of inbreeding on survival after infection with Vibrio parahaemolyticus were significant, as the cumulative mortality of shrimp in the control population (CP) was significantly lower than that in the F9 generation of EC5 inbred family during 24–72 h after infection with V. parahaemolyticus (P < .05). Additionally, the levels of antibacterial activity, immune enzymes including lysozyme (LZM) activity, alkaline phosphatase (AKP) activity and PO activity in cell-free haemolymph were significantly higher in the control population than those in the F9 generation 6 h after infection with V. parahaemolyticus (P < .05). Furthermore, the expression levels of anti-lipopolysaccharide factor (ALF), LZM, Tollip, evolutionarily conserved signaling intermediate in Toll pathway (ECSIT), Toll and signal transducer and activator of transcription (STAT) in the hepatopancreas, and Crustin, LZM and Tollip in haemocytes were significantly higher in the control population than those in the F9 generation after infection with V. parahaemolyticus (P < .05). These results suggested that the F9 generation has a weaker disease-resistant capability than the control population when infected with V. parahaemolyticus. In conclusion, this study demonstrates that a high level of inbreeding has a negative effect on growth-related traits and physiological health of E. carinicauda, thus highlighting the need to maintain genetic diversity in selective breeding programs.