盐度胁迫下曼氏无针乌贼的行为和生理响应

Behavioral and physiological responses of Sepiella japonica exposed to salinity changes

盐度变化会引起头足类动物渗透调节、免疫能力和激素分泌异常等一系列生理应激反应,同时还会引发应激诱导的喷墨行为等异常行为变化,最终可能导致头足类因渗透失衡出现大量死亡。结合头足类苗种繁育过程中因海水盐度波动出现的摄食及行为异常等问题,探究了盐度胁迫对曼氏无针乌贼(Sepiella japonica)行为活跃性、组织结构、渗透调节以及免疫相关酶活性的影响,明确了其对盐度变化的应激反应及适应能力。结果显示:在高盐胁迫下曼氏无针乌贼的行为活跃性显著增加(P<0.05),且倾向于绕水槽壁游动;与21‰组相比,27‰组和33‰组肌肉、鳃和肝脏组织结构呈现较严重的损伤,15‰组的各组织结构无明显变化;随着盐度的升高,鳃中Na^(+)/K^(+)-ATP酶活性呈现先降低后升高趋势(P<0.05);33‰组脑中皮质醇含量显著高于其他处理组(P<0.05);盐度升高或降低均会导致鳃和肝脏中超氧化物歧化酶(Superoxide dismutase,SOD)、过氧化氢酶(Catalase,CAT)活性显著升高(P<0.05),丙二醛(Malondialdehyde,MDA)含量显著增加(P<0.05),溶菌酶(Lysozyme,LZM)活性显著降低(P<0.05)。综合分析认为,曼氏无针乌贼具有较好的耐低盐能力,高盐胁迫会引发其类焦虑行为。此外,在研究设定的15‰—33‰盐度范围内,盐度变化还会引起其渗透调节以及免疫相关酶活性的改变。研究结果为阐释头足类适应盐度波动的调节机理,控制适宜的养殖环境提供了参考依据。

Sepiella japonica is an important commercial marine cuttlefish that is widely distributed around the coastal waters of the North-West Pacific and Northern Indian Ocean.The survival rate of the cuttlefish living in aquaculture farms may be subject to salinity fluctuations due to typhoons,rainstorms and tidal water flows.Changes in salinity may cause a series of physiological and behavioral stress responses in cephalopods,e.g.osmoregulation,immune capacity,hormone secretion and stress-induced inking behavior,and can even lead to mass deaths due to osmotic stress.Thus,during the process of seedling production of cephalopods,it is important to maintain the water salinity at the proper levels.To better understand the stress responses and the adaptability of cephalopods to cope with salinity stress,the changes in the behavioral activity,histopathology,osmoregulation and immune related enzymes of Sepiella japonica at different salinities of 15,21,27 and 33‰exposed to 48 h were investigated in this study.The results showed that the distance moved,average velocity,the frequency of accelerations,active time and manic time of Sepiella japonica increased significantly under high salinity stress(27‰)(P<0.05).The cuttlefish tended to swimming around the tank wall when they were exposed to high salinity(27‰).Compared to the control groups(21‰),cuttlefish from the 27‰and 33‰groups showed more serious disorder in the tissue structures of muscle,gill and liver,while no changes was found in the 15‰groups.With the increase in salinity,the activity of Na+/K+-ATPase in the gill decreased firstly and then increased(P<0.05).The cortisol content in brain tissue in the 33‰groups was significantly higher than that from the other treatment groups(P<0.05).The fluctuation of salinity could lead to the significant increase of activities of superoxide dismutase(SOD)and catalase(CAT)(P<0.05),the content of malondialdehyde(MDA)(P<0.05),and a significant decrease of activity of lysozyme(LZM)(P<0.05)in gills and liver.Based on these results,it can be concluded that the Sepiella japonica has good tolerance to low-salt conditions,but high-salt stress could cause serious inking behavior and anxiety-like behavior.In addition,the range of salinities used in this study(15‰—33‰)could cause adverse effects on osmoregulation and immune related enzymes for Sepiella japonica.The results of the study would provide a reference for elucidating the regulatory mechanisms used by cephalopods to cope with salinity stress,and also offer valuable information to hatchery managers to help keep appropriate culture environment for Sepiella japonica.