Effects on survival time of Fenneropenaeus chinensis challenged by different doses of WSSV and diets

White spot syndrome virus(WSSV)is one kind of destructive virus affecting shrimp industry in the world.Output of Fenneropenaeus chinensis which once was a staple species has been greatly affected by outbreak of WSSV since 1993 in China.To produce WSSV-resistance shrimp strains is an important approach to revive the shrimp industry.To select survived F.chinensis as broodstock via WSSV challenge test can increase the efficiency of breeding.However,mortality of shrimps could reach nearly 100% once they were infected with WSSV,which increases the difficulty for shrimp breeding.In this study for the purpose to reveal effect of different WSSV amount on F.chinensis,juvenile F.chinensis were infected with a certain amount of WSSV individually and the survival time and survival rate were observed.The results showed that survival time of shrimps infected with 5.2×108 copies,1.0×109 copies and 2.1×109 copies of WSSV respectively was 389.3,323.3 and 187.3 h and significant different(P0.01).The cumulative mortalities of all the shrimps finally reached 100%.The survival time increased while shrimps were fed with less WSSV bait.For the purpose to reveal the effect of diets on the ability for disease resistance,shrimps infected with WSSV were fed with different diets of live brine shrimps,commercial bait and fresh clam.It was showed that the survival time of infected shrimps fed with live brine shrimps,fresh clam and commercial bait respectively was 281.7,173.9 and 164.9 h.The survival time of infected shrimp fed with live brine shrimps was significantly higher than that fed by commercial bait and fresh clam respectively(P0.01).There was no significant difference of survival time between infected shrimps fed with commercial bait and fresh clam(P0.05).Cumulative mortalities of all the groups of infected shrimps that fed with different diets were 100%.Live brine shrimp is better than commercial bait and fresh clam for the purpose of enhancing shrimp WSSV resistance ability.