During tidal cycles, semi-terrestrial fiddler crabs are subject to alternating periods of submersion and desiccation. Here, we compare physiological and biochemical adjustments to forced submersion and desiccation in two fiddler crabs from the Galapagos archipelago: the indigenous Leptuca helleri, and Minuca galapagensis. We examine ecological distributions and habitat characteristics using transect analysis; survival after 6 h forced submersion at different salinities (0, 21 and 42 ‰S), and after 6 or 12 h desiccation challenge, including alterations in hemolymph osmolality; and, oxidative stress responses in the gills and hepatopancreas, accompanying glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) activities, and lipid peroxidase (LPO). We provide an integrated biomarker response (IBR) index for each species based on oxidative stress in each tissue and condition. Our transect study revealed that L. helleri occupies an intertidal niche while M. galapagensis is supralittoral, L. helleri being less resistant to submersion and desiccation. After 6 h submersion, L. helleri survived only at 21 ‰S while M. galapagensis survived at all salinities. Hemolymph osmolality decreased at 0 ‰S in M. galapagensis. After 6 h desiccation, osmolality decreased markedly in L. helleri but increased in M. galapagensis. Enzyme assays were not performed in L. helleri owing to high mortality on submersion/desiccation challenge. After submersion in M. galapagensis, hepatopancreas GPx activities decreased in 0 and 21 ‰S while GR activity was strongly inhibited at all salinities. Gill LPO decreased in 42 ‰S. On desiccation in L. helleri, GPx activity was inhibited in the hepatopancreas but increased in the gills. GST activity increased while LPO decreased in both tissues. After desiccation in M. galapagensis, hepatopancreas GPx activity increased. Both hepatopancreas and gill GST and GR activities and LPO were strongly inhibited. The IBR indexes for L. helleri were highest in fresh caught crabs, driven by gill and hepatopancreas LPO. For M. galapagensis, submersion at 21 ‰S contributed most to IBR, LPO in both tissues responding markedly. Leptuca helleri appears to be a habitat specialist adapted to a narrow set of niche dimensions while M. galapagensis survives over a much wider range, exhibiting little oxidative stress. The species' physiological flexibilities and limitations provide insights into how fiddler crabs might respond to global environmental change on semi-arid islands.

中文翻译：

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在半干旱岛上的生存：加拉帕戈斯群岛的提琴蟹的浸没和干燥耐受性

在潮汐周期中，半陆地提琴蟹会经历交替的浸没和干燥时期。在这里，我们比较了来自加拉帕戈斯群岛的两种提琴蟹的生理生化调整与强迫浸没和干燥的关系：本土Leptuca helleri和Minuca galapagensis。我们使用断面分析研究生态分布和生境特征；在不同盐度（0、21和42‰S）下被强迫淹没6小时后，以及在干燥挑战后6或12小时（包括血淋巴渗透压改变）后的存活率；以及ill和肝胰腺的氧化应激反应，并伴有谷胱甘肽过氧化物酶（GPx），谷胱甘肽S-转移酶（GST）和谷胱甘肽还原酶（GR）活性以及脂质过氧化物酶（LPO）。我们根据每个组织和状况中的氧化应激，为每个物种提供综合的生物标志物响应（IBR）指数。我们的样带研究表明，当加拉帕戈斯山毛虫处于水生上层时，H。helleri占据了潮间带的生态位，而L. helleri对淹没和干燥的抵抗力较小。浸入水中6小时后，黑黎丝菌仅在21‰S下存活，而加拉帕格氏菌在所有盐度下都存活。galapagensis的血淋巴渗透压在0‰S时降低。干燥6 h后，渗透压在hell。L.里显着下降，而在M. galapagensis中则上升。由于在淹没/干燥挑战中死亡率高，所以没有在黑麦草中进行酶分析。在加拉帕戈斯藻中浸没后，肝胰腺的GPx活性在0和21‰S处下降，而GR活性在所有盐度下均被强烈抑制。L LPO降低42‰S。干燥后，GPx活性在肝胰腺中受到抑制，但在g中增加。在两个组织中，GST活性增加而LPO减少。在加拉帕戈斯菌中干燥后，肝胰腺GPx活性增加。肝胰腺和g GST和GR活性以及LPO均受到强烈抑制。受g和肝胰腺LPO的驱动，在新鲜捕获的螃蟹中，H。helleri的IBR指数最高。对于galapagensis分枝杆菌，浸没在21‰S对两个组织的IBR，LPO贡献最大。Leptuca helleri似乎是适应狭窄生态位尺寸的生境专家，而galapagensis则可以在更宽的范围内生存，几乎没有氧化应激。该物种