Study On Tolerance And Immune Response Of Pacific Abalone Haliotis Discus Hannai During Simulated Air Exposure And Spawning Period

Pacific abalone,Haliotis discus hannai Ino,is one of economically important species in China and live abalone products are sold in domestic markets.However,live abalones are sealed in insulated containers for a long time for transportation,which may experience stressful conditions and be spoiled during this period.Therefore,this study would assess survival rate and weight loss rate(WLR)of abalone under various conditions to determine optimal condition for packaging transport.Parameters,including temperature,supplemental humidity and oxygen during simulating live transport were tested.The results showed that survival rate increased significantly after cold water shock and humidity controlled,while oxygen supplements does not have a significant effect.In addition,the WLR was significantly increased with increasing duration(P<0.05).Moreover,an experiment was added to investigate the stress response caused by air exposure.The hemocytes parameters,including total hemocytes count(THC),hemocytes mortality and reactive oxygen species(ROS)were estimated for 2,6,12,24 and 30 h after air exposure with different temperatures(5,10,20 and 28 ?)and then immediately re-immersed in seawater for 24 h recovery.The results showed that a significant decrease of THC was observed in Pacific abalone hemocytes following 30 h of air exposure at 5,10 ? and 24 h of air exposure at 20 ?.A significantly increase of hemocytes mortality and ROS were observed at 5 and 10 ? and it peaked after 30 h.Then the hemocytes mortality and ROS were gradually decreasing within subsequent 24 h of recovery period but they were also over the control levels.Therefore,these investigationscan serve as indicators of affect functional immune response and physiological stress of live abalone transportation.And part of anaerobic metabolism has measured the relationship of organic acids between blood pyruvate and blood lactate.The results showed that was increased blood lactate levels and the presence decreased blood pyruvate levels show in pyruvic acid levels of abalone plasma after simulated live transportation(tissue hypoxia),can be used as an early indicator of deteriorating conditions.Experiments investigated the potential of anaerobic metabolism in the abalone by subjecting the gastropod to plasma functional anoxia for 0,12,24,36 h on air exposure under different temperature(5,15 and 25 ?)and then immediately re-immersed in seawater for 24 h recovery period treatment were examined.The results showed that pyruvic acid level a gradually decreased at all the relative humidity(%RH)and reduced to minimum in 74-76%RH at 15 ? for 36 h.While,it was found that lactic acid or blood lactate level gradually increased with increasing duration,until the maximum level during 74-76%RH at 15 °C for 36 h also and then being gradually decreasing after subsequent 24 h of recovery period.Mortality is a major problem for sustainability of the aquaculture worldwide.Mortality usually resulted from complex interactions between the environmental stress and physiological status(i.e.water temperature,oxygen,diseases,spawning period).In terms of spawning period,the assessment on the maturity stage morphology and immunology of specimens is essential for the determination of the spawning strategy and reducing the risk of specimen mortality.This study investigated gonad morphology in Pacific abalone H.discus hannai.The results could be used to obtain detailed analysis concerning the development of gonad.In addition,different status(pre-spawning,spawning and four-times post spawning)of female and male samples were collected to estimate the effects of spawning on the immune response.The hemocytes parameters,including total hemocytes count(THC),hemocytes mortality,reactive oxygen species production(ROS)were hired using flow cytometry analysis.The results showed that THC decreased after spawning and it was lowest in 3 days post-spawning,after that it would gradually increase until 9 days post-spawning and increased close to pre-spawning level.Hemocytes mortality suffered great increased during spawning and it was highest in 3 days post-spawning samples.Moreover,Abalone reduced their metabolic activity after spawning which is reflected by increasing the reactive oxygen species in both males and females.The hypothesis that variability in abalone hemocytes during spawning period may more immediately be linked to individual metabolic condition than ambient changes.