Experimental Studies On The Swimming Performance And Physio-ecology Of Whiteleg Shrimp Litopenaeus Vannamei

This paper reviews the research advances regarding the swimming performance,effects of environmental factors on the swimming ability of aquatic animals, and theeffect of dissolved oxygen (DO) concentration on the physiological ecology incrustacean. This paper also investigate the effect of different measures on the criticalswimming speed of whiteleg shrimp Litopenaeus vannamei, measures the effects oftemperature, salinity and DO concentration on the critical swimming speed (Ucrit),swimming endurance, tail-flip speed (Stf) and physiological mechanisms of whitelegshrimp L. vannamei, and studies the effect of DO concentration on the growth,survival, oxygen consumption, respiratory metabolism, and oxidative stress ofwhiteleg shrimp L. vannamei. The main results are as follows:1. The effect of different measures on the critical swimming speed of whiteleg shrimpLitopenaeus vannameiIn the literature, the magnitude of the velocity increments (U2) and the prescribedtime interval for each swimming period (T2) vary considerably. These variations areimportant, as they can profoundly influence Ucritand by extension can profoundlyinfluence the results of intraspecific studies. This study is to compare the methods thathave been used in studies involving the critical swimming speed (Ucrit) of whitelegshrimp Litopenaeus vannamei. The Ucritof L. vannamei was determined in a flumetank at different body length (L1:6.5, L2:8.8, and L3:11.5cm), time interval (10,20,30,40, and50min) and velocity increment (1/2BL s-1,3/4BLs-1, and BL s-1). Timeinterval (T2) and velocity increment (U2) had significant effects on Ucritof L.vannamei in the three body length groups. For L1the Ucritdecreased and thenincreased as the time interval increased, whereas no significant differences occurredin this BL group. For L2, when the T2ranges between10and30min, the Ucritin U2of1/2BL s-1were significantly higher than those in the other velocity increment groups. The Ucritdecreased as the T2increased in the U2of1/2BL s-1, and the Ucritdecreasedand then increased as the T2increased in the U2of3/4BL s-1, whereas Ucritshowed nosignificant differences with the time interval in the U2of BL s-1. For L3the Ucritat U2of1/2BL s-1in T2of10and20min were significantly higher than those in the othervelocity increment groups. The Ucritdecreased as the T2increased in the U2of1/2BLs-1, whereas Ucritshowed no significant differences with time interval in the othervelocity increment groups. The standard critical swimming speed of L. vannamei wasachieved at T2of20min and U2of1/2BL s-1in all three BL groups2. The effect of temperature on the critical swimming speed (Ucrit) and physiologicresponse of whiteleg shrimp Litopenaeus vannameiThe effect of different temperature (17,20,25, and29℃) on the criticalswimming speed (Ucirt) of whiteleg shrimp Litopenaeus vannamei was determinedunder laboratory conditions. Metabolite concentrations in plasma were measuredbefore and immediately after swimming fatigue to evaluate the physiologic effects offatigue in L. vannamei. Temperature significantly affects on the Ucritof L. vannamei.The Ucritspeed of L. vannamei increased as the temperature increased. Therelationship between temperature and Ucirtcan be described by the linear model asUcirt=1.5916t+0.8892，R2=0.9992, and the Ucirtof shrimps in different temperatureswere significantly different. The plasma glucose concentration of shrimps at17℃was significantly higher than those in the other temperature groups. After swimmingfatigue, the plasma glucose concentration of shrimps at20and25℃increasedsignificantly. The Swimming fatigue leads to severe loss of plasma total proteinconcentration in28℃, whereas the plasma lactate levels of L. vannamei increased at25and28℃after swimming fatigue. The maximum critical swimming speed of L.vannamei was at temperature29℃.3. The effect of salinity on the critical swimming speed (Ucrit), tail-flip speed (Stf) andphysiologic response of whiteleg shrimp Litopenaeus vannameiThe critical swimming speed (Ucrit) and tail-flip speed (Stf) of whiteleg shrimpLitopenaeus vannamei that were exposed to various salinities (20‰,25‰,30‰,35‰,and40‰) were determined under laboratory conditions. Metabolite concentrations in the plasma, muscles, and hepatopancreas were measured before and immediately afterfatigue to evaluate the physiologic effects of fatigue in L. vannamei. Salinity affectsthe Ucritand Stfof L. vannamei. The Ucritand Stfincreased and subsequently decreasedas salinity increased from20‰to40‰. The relationship between salinity (s,‰) andUcritor Stfcan be described by the quadratic model as Ucirt=-0.0171s2+1.2371s+20.497，R2=0.7667; Stf=-0.2386s2+15.528s-145.12, R2=0.9693. The optimumsalinity and corresponding maximum Ucirtwere36.17‰and42.87cm/s, respectively.The optimum salinity and corresponding maximum Stfwere32.54‰and107.52cm/s,respectively. The different salinities directly affected the physiology of the shrimp,inducing changes in hepatopancreas total protein, plasma total protein, abdominalmuscle lactate, plasma lactate, plasma glucose, hepatopancreas glycogen, andabdominal muscle glycogen concentration. Fatigue from swimming led to severe lossof plasma total protein levels under20,25,30, and35‰salinity. Fatigue fromtail-flip led to severe loss of hepatopancreas glycogen under20‰salinity and plasmaglucose under25‰,30‰, and35‰salinity. The triglyceride and lactate in theplasma concentration increased significantly in a range of salinities after tail-flip.These results are of particular value in evaluating the locomotory ability of whitelegshrimp in different salinities and understanding its ecological processes to improvecapture and rearing techniques.4. The effect of dissolved oxygen concentration on the swimming ability andphysiologic response of whiteleg shrimp Litopenaeus vannameiIn the DO concentration experiment, the effect of different dissolved oxygen(DO) levels (2.0±0.3mg/L, T1;3.8±0.4mg/L, T2;6.8±0.7mg/L, T3and13.6±2.1mg/L, T4) on the critical swimming speed (Ucrit), tail-flip speed (Stf), and swimmingendurance of whiteleg shrimp Litopenaeus vannamei was tested under laboratoryconditions. Metabolite concentrations in plasma and tissues of the experimentalshrimp were measured at control and subsequent recovery after swimming fatigue toevaluate the physiologic response of L. vannamei. Using a swimming flume, theendurance was tested at swimming speeds ranging from v1to v5.The power model(ν·tb=a) can be used to show the relationship between swimming endurance and swimming speed at any of DO concentration tested. The swimming ability index(SAI), defined as SAI=∫90000vdt (cm), was found to be DO-dependent in L.vannamei. The Ucrit,Stf, and SAI all increased as the DO concentration increased from1.9mg/L to13.6mg/L. The relationship among those can be described by the powermodel as Ucrit=31.534DO0.0788, R2=0.9805; Stf=75.621DO0.1753, R2=0.9981; andSAI=27.947DO0.137, R2=0.9312.The different DO concentrations directly affected the physiology of the shrimp.Lower DO concentration led to an increase in lactate and energy charge. Fatigue fromtail-flip led to a severe loss of plasma glucose under T1and T2, and the plasma lactateconcentration increased significantly in all DO groups. The tail-flip fatigue ofL.vannamei in the present study may be due to the accumulation of lactate in theplasma. L．vannamei responded to experimental lower DO and swimming stress withclassical anaerobic metabolism mainly characterized by an decrease in total protein,utilization of glycogen and triglyceride, and accumulation of lactate. At higher oxygenconcentrations, the swimming ability of the shrimp could be determined by theirmuscular capabilities or energy source. During recovery the shrimp maintained athigher DO concentration removed lactate and recovered energy charge to pre-exerciselevels more quickly than shrimp maintained at lower DO concentration. L vannameiexposed to lower DO concentrations showed a lower capacity for glyconeogenesis,accumulation of lactate, and a slow replenishment of energy charge, implying thatanaerobic glycolysis made a significant contribution to the recovery. These results areof particular value in evaluating the locomotory ability of whiteleg shrimp in differentDO concentrations and understanding its ecological processes to improve capture andrearing techniques.5. The effect of dissolved oxygen (DO) concentration on the growth and thephysiologic mechanism of whiteleg shrimp Litopenaeus vannameiHypoxic or hyperoxic exposure can affect the physiological capabilities anddefine regulatory limits. Based on the effect of DO on the swimming ability ofwhiteleg shrimp Litopenaeus vannamei, the effect of different dissolved oxygen (DO) levels (2.0±0.3mg/L, T1;4.2±0.3mg/L, T2;6.8±0.7mg/L, T3and13.6±2.1mg/L,T4) on the growth and digestive enzyme activities, respiratory metabolism, energymetabolism and oxidative stress of L. vannamei were tested under25℃. Theexperiment lasted for30d.The results showed that when DO was below4.2mg/L, the growth of shrimpwas depressed. The feed conversion efficiency and digestive enzyme activitydecreased with the decrease of DO, and both of them in T4were significantly higherthan those in the other DO groups. The survival rate of shrimp in T4was higher thanthat in the other DO groups. The lethal dissolved oxygen (LDO) content of the shrimpin T1and T2were significantly lower than those in T3and T4, whereas therespiratory frequency decreased as the DO increased. The relationship between DO(mg/L) and gill weight per unit body weight (Rgw) can be described by the powermodel as: Rgw=1.2379DO-0.0786, R2=0.7826. Both oxygen consumption andammonia-N excretion by L. vannamei increased with increasing DO levels, whereasthe trend was found to be reversed in O:N. In T1and T2, the levels of the total protein,glucose, triglyceride, and lactate in plasma and the total protein and lactate inhepatopancreas of the shrimp were significantly higher than that in T3and T4. Theresults showed that when the shrimp are stressed by severe hypoxia the originalrespiration rate can not be maintained, and the shrimps have to resort to anaerobicrespiration. Most parameters were returned to homeostasis after15d of experiment.In T1and T2, the levels of malondialdehyde (MDA) in plasma and tissues of theshrimp were significantly lower than that in T3, and activities of anti-superoxideradical and superoxide dismutase (SOD) and the total antioxidant capacity status intissues were significantly lower than those in the other DO groups. In T4, the levels ofMDA in plasma of the shrimp was significantly lower than that in T3, whereas thetotal antioxidant capacity status in muscle of the shrimp was significantly higher thanthose in other DO groups.The results indicated that DO was an important factor affecting the amount andfitness of shrimp stock because hypoxia could cause a high rate of mortality andgrowth depression and higher DO could enhance the feed digestive activity and survival rate. The decreased oxygen consumption and ammonia-N excretion,increased respiratory frequency and transient increases in metabolic demand mayaccount for shrimp hypoxic tolerance. The noted tissue specificities of the oxidativestress most likely reflected different metabolic activities and different responses toenvironmental conditions in the examined tissues. A scheme on possible ways ofregulating antioxidant enzymes by different oxygen levels is proposed. Under thecondition of25.0±0.5°C, salinity32±1, L. vannamei showed an ability to tolerate andadapt to the change of DO concentrations.6. The application of study on the swimming ability of penaeid shrimpAccording to the results of the effects of temperature, salinity and dissolvedoxygen levels on the swimming ability of L.vannamei, the application of swimmingability in the shrimp were discussed in this chapter. The different environmentalfactors significantly affect the swimming ability of the shrimp. Knowledge of themaximum swimming speed and swimming endurance is important because itinfluences the ability or otherwise of shrimp to escape from various parts of the trawl.The swimming capability of shrimp also plays an important role in selecting size inshrimp stock enhancement and live transport of the shrimp. A visual software packagewas designed for swimming ability to determine the critical swimming speed andtail-flip speed at different temperature, salinity, DO and body length. A newtransportation device was designed for live transport of the shrimp based on theswimming ability, containing a recirculating system to reduce intraspecific aggression,and provision for water exchange, aeration and securing the shrimp.