Effects of salinity on spawning and larval development of Exopalaemon carinicauda

Female Exopalaemon carinicauda at ovarian maturation stage Ⅱ rearing by artificial propagation in the laboratory were chosen as test material. The shrimps were gradually acclimated to the experimental salinity levels of 2,5,10,15,20,25 and 30 to determine the effects of salinity on spawning,embryonic development and larval growth of E. carinicauda. The results showed that the ovaries of female E. carinicauda could mature at all test salinity levels. However,it failed to spawn at salinity 2. Salinity levels from 10 to 20 were the most favorable for female E. carinicauda spawning. Although larval development was most successful in eggs incubated at salinity levels of 5to 30,embryonic development were significantly affected by salinity,and the egg incubation period was shorter at salinities of 15,20 and 25 than at the other salinities. There were no significant effects of salinity on the rates of larval metamorphosis and survival,but the dry mass of individuals was significantly affected by salinity. The dry mass of shrimps reared at salinities of 15 and 20 were significantly higher than at the other salinities. The growth of 20-day old shrimps was significantly affected by salinity. The specific growth rate increased with the increasing salinity level from 5 to20,and then decreased at the salinity above 20. The mRNA level of gill Na+-K+-ATPase was high at high and low salinities,and the lowest at the theoretical salinity 17. 5,which might be equal to the hemolymph osmotic pressure of E. carinicauda. It was implied that female parent E. carinicauda could reproduce in a wide range of salinities,while 20-day old shrimps presented higher growth rates at salinities near its theoretical isosmotic point.