盐度胁迫对三疣梭子蟹(Portunus trituberculatus)鳃中游离氨基酸含量的影响

本研究分析了不同盐度环境下三疣梭子蟹(Portunus trituberculatus)鳃组织中游离氨基酸(FAAs)的含量及浓度变化规律，明确 FAAs 的组成及其在盐度适应中发挥的功能。结果显示，在正常海水中，三疣梭子蟹鳃组织中牛磺酸(Tau)的浓度最高(2.54 mg/g)，其次分别为丙氨酸(Ala,0.65 mg/g)、谷氨酸(Glu,0.64 mg/g)、精氨酸(Arg,0.58 mg/g)、甘氨酸(Gly,0.48 mg/g)和脯氨酸(Pro,0.25 mg/g)；在盐度10–50范围内，梭子蟹鳃中总游离氨基酸(TOFAA)的含量随盐度的增加而显著升高(P<0.05)，盐度50时，TOFAA 的含量为盐度10时的1.48倍。进一步分析发现，非必需氨基酸(NEAA)(Gly、Glu、Ala 和 Pro)的浓度随盐度的升高而上升，而必需氨基酸(EAA)的浓度变化不显著(P>0.05)。研究表明，FAAs 在三疣梭子蟹盐度适应中具有重要功能，其中发挥渗透调节功能的主要为 NEAA。

Effects of Different Salinities on the Free Amino Acids Composition in the Gill of Portunus trituberculatus

In this study, we investigated the composition and function of free amino acids (FAAs) in the gill of Portunus trituberculatus under different salinities. In a 5-day experiment, the contents of FAAs were measured under a series of salinities. We found that in seawater-adapted P. trituberculatus, the concentration of taurine (2.54 mg/g) was the highest, followed by alanine (0.65 mg/g), glutamate (0.64 mg/g), arginine (0.58 mg/g), glycine (0.48 mg/g) and proline (0.25 mg/g). The level of total free amino acids (TOFAA) in the gill increased significantly with the rise in salinity (P<0.05). When salinity was 10, 20, 33, 40, and 50, the concentration of TOFAA in the gill was 5.32 mg/g, 7.26 mg/g, 6.34 mg/g, 7.25 mg/g, and 7.90 mg/g respectively. Non-essential amino acids (NEAA) increased significantly as the salinity was elevated from 10 to 50. Essential amino acids (EAA) was not affected by external salinity change (P>0.05). NEAA includes glutamate (Glu), alanine (Ala), glycine (Gly), aspartic acid (Asp), serine (Ser), cysteine (Cys), tyrosine (Tyr), proline (Pro), and Tauine (Tau), and the rest are EAA. TAA include aspartic acid (Asp), glutamate (Glu), glycine (Gly), and alanine (Ala). The concentrations of free Gly, Glu, Ala, Pro in the gill of P. trituberculatus were raised sharply (P<0.05) with the increase in salinity, whereas the concentration of free Arg decreased (P<0.05). The results suggested that FAAs, especially individual Gly, Glu, Ala, and Arg, could play an important role in salinity adaption. During adaptation, the FAAs pool (mainly NEAA) in the gill may be directly associated to osmoregulation. Change in the FAAs pool in the gill after acclimatization suggested that mainly NEAA might be involved in intracellular osmoregulation. It was also demonstrated that the salinity change mainly affected the NEAA content in the gill.