Ecological And Physiological Mechanisms On Typical Environmental Factors In Sea Cucumber, Apostichopus Japonicus Selenka

1. Sea cucumber (Apostichopus japonicus Selenka) is an important marine culturespecies in northern China. Using experimental ecology methods, the influence ofdifferent temperature fluctuation modes and intensities and directions to heat shockprotein70(Hsp70) were studied. The results are as follows:(1). Hsp70contentsincreased rapidly initially under different temperature fluctuation modes intemperature increase treatment.(2). Hsp70contents decreased as temperature turnsback to normal level, the R24and R20group got no significant difference with thecontrol group(P>0.05) at72h and48h, respectively.(3) Hsp70contents increased\apidly and maintained at a high level in consecutive heating-up treatment, whichillustrate that Hsp70contents can be continuous expressed with consecutivetemperature stimulus.(4) The induction of Hsp70is in connection with not only thecontinuity of temperature changing but also the intensities of temperature fluctuation.The more the temperature changed, the quicker and the more Hsp70was induced.(5)In this experiment, Hsp70contents increased rapidly after2h in temperature-uptreatment while increased slowly in temperature-drop treatment and didn’t reach thepeak value until8h. Therefore we estimated that Hsp70was more sensitive to thetemperature-up treatment than to the temperature-drop treatment. In conclusion, moreresearch based on this experiment should be done to fully understand the laws ofexpress for heat shock protein under more complicated condition which is similarwith the natural environment.2. The influence of chronic stress of ammonical nitrogen on the activities of immunoenzymes (acidic phosphatase (ACP), alkaline phosphatase (AKP), catalase(CAT) and superoxide dismutase (SOD) and heat shock protein70(Hsp70) contentwere investigated in Sea Cucumber, Apostichopus japonicus Selenka. Body wall andcoelomic fluid samples of sea cucumbers in5ammonical nitrogen concentration(ANC) groups (0.51、2.04、5.09、10.19and50.93mg/L) were collected anddetermined every5days till the20thday. ACP and AKP activities in both tissuesincreased at first and decreased afterwards in0.51and2.04mg/L groups whiledecreased in5.09、10.19and50.93mg/L groups. CAT activities in body walldecreased in all5groups and were reversely correlated with ANC, while those incoelomic fluid decreased in0.51、5.09、10.19and50.93mg/L groups. SOD activitiesin both tissues increased firstly and then decreased in0.51、2.04、5.09mg/L groupswhile those were reversely correlated with ANC in high concentrations. Hsp70content in body wall, intestine, respiratory tree and coelomic fluid rose rapidly underammonical nitrogen stress and peaked on the5thday. The Hsp70content were stillmarked higher than the control on the20thday (P<0.05). The maximum Hsp70content in4tissues weas positively correlated with ANC. All the results indicated theactivities of immunoenzymes tended to decrease and the non-specific immune systemof sea cucumbers were damaged as ANC increased and time went by. However, Hsp70concentration maintained high level, which was important to promote the stressresistance of sea cucumbers.3. Growth, metabolism and physiological responses of sea cucumber, Apostichopusjaponicus Selenka, during periods of inactivity, were investigated in this study. Thebody weight, oxygen consumption rate (OCR), activities of immunoenzymesincluding acidic phosphatase (ACP), alkaline phosphatase (AKP), catalase (CAT) andsuperoxide dismutase (SOD), and Heat shock protein70(Hsp70) contents in bodywall and coelomic fluid were measured to evaluate the growth, metabolism andphysiological responses of A. japonicus during starvation, experimental aestivationand aestivation. The results showed that body weight of sea cucumbers in all threetreatments dropped significantly (P <0.05). OCR reduced in starvation, experimental aestivation treatments but increased gradually in aestivation group. Both ACP andAKP activities in all treatments decreased gradually, and SOD and CAT activities andHsp70contents in starvation and experimental aestivation treatments decreased,however, SOD and CAT activities and Hsp70contents increased in aestivationtreatment. Results of this study indicated that growth, metabolism and physiologicalresponses declined in A. japonicus due to the stress of fasting. The sea cucumber A.japonicus enters a state of aestivation when the temperature is maintained at24°C.However, the experimental aestivation is different from aestivation to some extent inmetabolism and physiological responses. This suggest that the mechanism ofaestivation in A. japonicus is complex and may not be attributed only toenvironmental changes, such as temperature, as shown in previous studies.4. Sea cucumber (Apostichopus japonicus Selenka) is an important marine culturespecies in northern China. Using experimental ecology methods, the influence ofdifferent transportation densities and temperatures (10℃、15℃、20℃) and duration(<24h) were to behaviors and evisceration and survival of A. japonicus juveniles werestudied, and the critical densities under different temperatures were determined toinvestigate the influence of different transportation densities and temperatures (10℃、15℃、20℃) and duration to physiological parameters and response mechanism of A.japonicus juveniles. The results showed that as an acute environmental stress undermulti-factor synergy, transportation densities and temperatures and durationsignificantly influence the behaviors and survival and physiological parameters of A.japonicus. It’s feasible to transport A. japonicus juveniles using plastic sea water bagswith oxygen under high densities. Low temperature (10℃) is benefit to increasetransportation density (140juveniles per bag) and prolong duration (24h), however,shock duration will be prolonged and recovery will be delayed under this conditions.Our results showed that transportation at densities of140juveniles per bag (2L water,4L oxygen) for24h at10℃is feasible, but we recommend transportation for A.japonicus juveniles at more conservative densities and durations where possible tominimize transportation stress. 5. The growth, metabolism and immune responses of sea cucumber, Apostichopusjaponicus Selenka, following evisceration induced artificially, were investigated inthis study. The body weight, specific growth rate (SGR), oxygen consumption rate(OCR), activities of immunoenzymes including acidic phosphatase (ACP), alkalinephosphatase (AKP), catalase (CAT) and superoxide dismutase (SOD), totalantioxidant capacity (T-AOC) and malonyl-dialdehyde (MDA) in muscle, intestineand respiratory tree were measured to evaluate the physiological responses of A.japonicus to evisceration and the regeneration of viscera. The results showed that thebody weight of sea cucumber significantly dropped following evisceration and thenincreased gradually with digestive function resumed. Accelerated growth rates wereobserved in the regeneration group from the10thday to20thday, but there was nosignificant difference between the regeneration group and control group at the end ofthe experiment. As for OCR, it reduced rapidly after evisceration, then increasedgradually afterwards. Compared to the control, no significant difference in OCR wasfound on the45thday (P>0.05). The immune responses of A. japonicus were highlytissue-specific during the regeneration of the viscera. Both ACP and AKP activities inmuscle enhanced and peaked on the10thday, then decreased gradually to normal levelon the45thday (P>0.05). ACP and AKP activities in the regenerated tissuesexhibited a differential rising trend from the20thday after evisceration. SOD activityin muscle was not significantly influenced by evisceration with respected to thecontrol; however, those in the regenerated tissues significantly enhanced and weresignificantly higher than those in the control on the45thday (P <0.01). CAT activityin muscle of the regeneration group was significantly higher than that in the controlduring the whole period of the experiment (P <0.05). CAT activity in the regeneratedrespiration tree enhanced invariably after evisceration, while that in the intestine werenot significantly affected by evisceration (P>0.05). Significant increase was found inboth T-AOC and MDA in all three tissues after evisceration (P <0.05), however, theyall returned to normal at the end of the experiment. The results of this study indicatedthat the growth, metabolism and immune responses in sea cucumber weresignificantly influenced by evisceration. Although the regeneration group did not catch up with the control in body weight, SGR, OCR and major non-specific immuneparameters have resumed to normal level within45days after evisceration, whichmight mean that A. japonicus has recovered in physiology from evisceration.