Hu Marian Y, Guh Ying-Jey, Shao Yi-Ta, Kuan Pou-Long, Chen Guan-Lin, Lee Jay-Ron, Jeng Ming-Shiou, Tseng Yung-Che
Institute of Cellular and Organismic Biology, Academia SinicaTaipei, Taiwan; Institute of Physiology, Christian-Albrechts University KielKiel, Germany.
Institute of Biological Chemistry, Academia Sinica Taipei, Taiwan.
Front Physiol. 2016 Feb 1;7:14. doi: 10.3389/fphys.2016.00014. eCollection 2016.
Hydrothermal vent organisms have evolved physiological adaptations to cope with extreme abiotic conditions including temperature and pH. To date, acid-base regulatory abilities of vent organisms are poorly investigated, although this physiological feature is essential for survival in low pH environments. We report the acid-base regulatory mechanisms of a hydrothermal vent crab, Xenograpsus testudinatus, endemic to highly acidic shallow-water vent habitats with average environment pH-values ranging between 5.4 and 6.6. Within a few hours, X. testudinatus restores extracellular pH (pHe) in response to environmental acidification of pH 6.5 (1.78 kPa pCO2) accompanied by an increase in blood [Formula: see text] levels from 8.8 ± 0.3 to 31 ± 6 mM. Branchial Na(+)/K(+)-ATPase (NKA) and V-type H(+)-ATPase (VHA), the major ion pumps involved in branchial acid-base regulation, showed dynamic increases in response to acidified conditions on the mRNA, protein and activity level. Immunohistochemical analyses demonstrate the presence of NKA in basolateral membranes, whereas the VHA is predominantly localized in cytoplasmic vesicles of branchial epithelial- and pillar-cells. X. testudinatus is closely related to other strong osmo-regulating brachyurans, which is also reflected in the phylogeny of the NKA. Accordingly, our results suggest that the evolution of strong ion regulatory abilities in brachyuran crabs that allowed the occupation of ecological niches in euryhaline, freshwater, and terrestrial habitats are probably also linked to substantial acid-base regulatory abilities. This physiological trait allowed X. testudinatus to successfully inhabit one of the world's most acidic marine environments.
热液喷口生物已经进化出了生理适应性，以应对包括温度和pH值在内的极端非生物条件。尽管酸碱调节能力是在低pH环境中生存的关键生理特征，但迄今为止，对喷口生物的酸碱调节能力研究甚少。我们报告了一种热液喷口蟹——龟甲扇蟹（Xenograpsus testudinatus）的酸碱调节机制，这种蟹原产于平均环境pH值在5.4至6.6之间的高酸性浅水喷口栖息地。在几个小时内，龟甲扇蟹会对pH值为6.5（pCO2为1.78 kPa）的环境酸化做出反应，恢复细胞外pH值（pHe），同时血液[公式：见正文]水平从8.8±0.3 mM增加到31±6 mM。鳃中的Na(+)/K(+)-ATP酶（NKA）和V型H(+)-ATP酶（VHA）是参与鳃酸碱调节的主要离子泵，在mRNA、蛋白质和活性水平上，它们对酸化条件会出现动态增加。免疫组织化学分析表明，NKA存在于基底外侧膜中，而VHA主要定位于鳃上皮细胞和柱状细胞的细胞质囊泡中。龟甲扇蟹与其他强大的渗透调节短尾类动物密切相关，这也反映在NKA的系统发育中。因此，我们的结果表明，短尾类螃蟹强大的离子调节能力的进化使它们能够占据广盐性、淡水和陆地栖息地的生态位，这可能也与强大的酸碱调节能力有关。这种生理特征使龟甲扇蟹能够成功栖息在世界上最酸性的海洋环境之一。
