Research Of Cost Of Reproduction And Adaptation Strategy Of Sea Cucumber Apostichopus Japonicus

The sea cucumber Apostichopus japonicus is the most economically important and valuable species in China.Reproduction is a key stage of animal life history.Reproduction can present behavioural and physiological challenges for animals,and causes negative fitness consequence.The negative consequences are referred to as the cost of reproduction.In this study,using bioenergetic analysis technology,behavioural analysis software and ultra performance liquid chromatography and quadrupole time-of-flight mass spectrometry?UPLC-Q-TOF-MS?,we analysed the energetic cost,behavioural cost and physiological cost in A.japonicus.Main results are as follows:1.Energetic cost and adaptation strategy of sea cucumber Apostichopus japonicus during reproductionEnergetic cost during breeding was explored in the A.japonicus.The food intake,digestive functions,and energy budget patterns were estimated at different breeding stages.Unexpectedly,in the growing gonad phase of the sea cucumber lifecycle,animals showed a decline in feed consumption(from 4.49 g ind^-1 day^-11 to2.6 g ind^-1 day^-1),ingestion rate(from 0.4 g g^-1 day^-11 to 0.13 g g^-1 day^-1),and apparent digestive rate?from 14.73%to 10.92%?,resulting in a reduced energy input.In addition,the increased energy investment in reproduction?from 1.76%to 15.61%?resulted in a decrease in energy allocated to soma growth?from 17.1%to 5.64%?and self-maintenance?from 47.82%to 34.67%?.These results suggest that reproduction impairs energy acquisition ability in breeding A.japonicus.And broodstock can adapt energy shortage by internal adjustment of energy allocation strategy.2.Locomotor cost and adaptation strategy of sea cucumber Apostichopus japonicus during reproductionLocomotor cost during breeding was explored in the A.japonicus.The total distance moved,cumulative duration of moving,moving frequency and maximum velocity were estimated at different breeding stages.The results showed that reproduction had no negative effects on locomotion frequency or maximum velocity.However,the total distance moved?from 32.04 m to 15.82 m?and cumulative duration of moving?from 12 h to 6.46 h?gradually decreased.Therefore,the results suggest that loss of locomotor endurance is the behavioural cost for reproduction in female A.japonicus.In addition,metabolism in muscle tissue of animals between the non-breeding stage and the growth stage was tested with ultra performance liquid chromatographyandquadrupoletime-of-flightmassspectrometry?UPLC-Q-TOF-MS?.There were 10 significant metabolic changes found in the muscle tissue of animals in the growth stage.Nine of these?e.g.lysoPCs and L-octanoylcarnitine?were higher during the growth stage and only one?e.g.lysoPE?was higher during the non-breeding stage.These data suggest that oxidative stress and lipid metabolism are potential physiological mechanisms linking reproduction and depressed locomotory performance during reproduction.And behavioral flexibility plays key role in adapting to negative consequences resulting from reproduction.3.Cost of metabolic physiology and adaptation strategy of sea cucumber Apostichopus japonicus during reproductionMetabolic cost during breeding was explored in the A.japonicus.The oxygen consumption rate,respiratory rate and enzyme activity of respiratory tree were estimated between non-breeding stage and the breeding stage.The results showed that oxygen consumption rate(from 11.84?g g^-11 h^-11 to 23.34?g g^-11 h^-1)and respiratory rate?from 6.22 breaths per min to 10.15 breaths per min?increased significantly at breeding stage.The ATP content in respiratory tree decreased at breeding stage,however,the Na⁺/K⁺-ATPase enzyme activity of respiratory tree increased at breeding stage.In addition,metabolism in respiratory tree tissue of animals between the non-breeding stage and the growth stage was tested with UPLC-Q-TOF-MS.There were 23 significant metabolic changes found in the respiratory tree tissue of animals in the growth stage.13 of these?e.g.deoxycorticosterone?were higher during the growth stage and 10 of these?e.g.eicosatrienoic acid?were higher during the non-breeding stage.These data suggest that oxidative stress is the potential physiological mechanisms linking reproduction and elevated respiratory performance during reproduction.And behavioral flexibility and physiological flexibility play key role in adapting to high oxygen demand during reproduction.4.Cost of digestive physiology and adaptation strategy of sea cucumber Apostichopus japonicus during reproductionPhysiological cost during breeding was explored in the A.japonicus.The feces mass,carbon content of feces,nitrogen content of feces and enzyme activity of gut tissue were estimated at different breeding stages.The results showed that carbon?from 1.66%to 2.68%?and nitrogen?from 0.39%to 0.48%?content of feces increased significantly at breeding stage,suggesting that reproduction depress digestive ability in A.japonicus.The activities of amylase enzyme(from 2.96 U mg^-1protein^-1 to 1.41 U mg^-11 protein^-1)and trypsin enzyme(from U mg^-11 protein^-1 to 42.78U mg^-11 protein^-1)decreased significantly at breeding stage,suggesting that reproduction depress digestive physiology in A.japonicus.In addition,metabolism in respiratory tree tissue of animals between the non-breeding stage and the growth stage was tested with UPLC-Q-TOF-MS.There were 31 significant metabolic changes found in the gut tissue of animals in the growth stage and mature stage.8 of these?e.g.serotonin and lysoPCs?were both higher during the growth stage and mature stage.However,4 of these?e.g.uridine monophosphate?were both higher during the non-breeding stage.These data suggest that oxidative stress and gut degradation are the potential physiological mechanisms linking reproduction and depressed digestive performance during reproduction.And feeding preference may play key role in adapting to high nutrient demand during reproduction.