title: Strong Ion Regulatory Abilities Enable the Crab Xenograpsus testudinatus to Inhabit Highly Acidified Marine Vent Systems.
abstract: 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.
authors: Institute of Cellular and Organismic Biology, Academia SinicaTaipei, Taiwan; Institute of Physiology, Christian-Albrechts University KielKiel, Germany.
authors: Marian Y
authors: MY
authors: Hu
authors: Institute of Biological Chemistry, Academia Sinica Taipei, Taiwan.
authors: Ying-Jey
authors: YJ
authors: Guh
authors: Institute of Marine Biology, National Taiwan Ocean University Keelung, Taiwan.
authors: Yi-Ta
authors: YT
authors: Shao
authors: Department of Life Science, National Taiwan Normal University Taipei, Taiwan.
authors: Pou-Long
authors: PL
authors: Kuan
authors: Department of Life Science, National Taiwan Normal University Taipei, Taiwan.
authors: Guan-Lin
authors: GL
authors: Chen
authors: Institute of Cellular and Organismic Biology, Academia Sinica Taipei, Taiwan.
authors: Jay-Ron
authors: JR
authors: Lee
authors: Biodiversity Research Center, Academia Sinica Taipei, Taiwan.
authors: Ming-Shiou
authors: MS
authors: Jeng
authors: Department of Life Science, National Taiwan Normal University Taipei, Taiwan.
authors: Yung-Che
authors: YC
authors: Tseng
keywords: Na+/K+-ATPase; V-type H+-ATPase; crustacean; gill; hydrothermal vent; hypercapnia; invertebrate physiology