Hydrogen sulfide (H2S) is a potent respiratory toxin that makes sulfidic environments tolerable to only a few organisms. We report the presence of fishes (Kryptolebias marmoratus, Poecilia orri, Gambusia sp., and Dormitator maculatus) in Belizean mangrove pools with extremely high H2S concentrations (up to 1,166 μM) that would be lethal for most fishes. Thus, we asked whether the three most prevalent species (Kryptolebias, Poecilia, and Gambusia) persist in sulfidic pools because they are exceptionally H2S tolerant and/or because they can leave water (emerse) and completely avoid H2S. We show that both physiological tolerance and emersion behavior are important. Kryptolebias demonstrated high H2S tolerance, as they lost equilibrium significantly later than Poecilia and Gambusia during H2S exposure ( 1,188±21 μM H2S). However, the fact that all species lost equilibrium at an ecologically relevant [H2S] suggests that physiological tolerance may suffice at moderate H2S concentrations but that another strategy is required to endure higher concentrations. In support of the avoidance behavior hypothesis, H2S elicited an emersion response in all species. Kryptolebias was most sensitive to H2S and emersed at H2S concentrations 52% and 34% lower than Poecilia and Gambusia, respectively. Moreover, H2S exposure caused Kryptolebias to emerse more frequently and spend more time out of water compared to control conditions. We suggest that physiological H2S tolerance and emersion behavior are complementary strategies. The superior H2S tolerance and amphibious capability of Kryptolebias may explain why this species was more prevalent in H2S-rich environments than other local fishes.

中文翻译：

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红树林鱼在硫化环境中依赖于浮游行为和生理耐受性。

硫化氢（H2S）是一种强力的呼吸道毒素，使硫化环境仅能耐受少数几种生物。我们报告在伯利兹红树林池中存在鱼类（Kryptolebias marmoratus，Poecilia orri，Gambusia sp。和Dormitator maculatus），这些鱼类的H2S浓度极高（高达1,166μM），对大多数鱼类来说都是致命的。因此，我们询问三个最普遍的物种（K虫属，Poecilia和Gambusia）是否在硫化物池中持续存在，因为它们对H2S的耐受性极强，并且/或者因为它们可以离开水（冒泡）并完全避免H2S。我们表明，生理耐受性和出苗行为都很重要。rypto虫具有很高的H2S耐受性，因为在H2S暴露期间，它们失去平衡的时间明显晚于Poecilia和Gambusia（1,188±21μMH2S）。但是，所有物种在生态上相关的[H2S]失去平衡的事实表明，在中等H2S浓度下生理耐受性可能就足够了，但是需要另一种策略才能承受更高的浓度。为了支持回避行为假说，H2S引发了所有物种的爆发反应。rypto虫对H2S最敏感，在H2S浓度下分别比Poecilia和Gambusia低52％和34％。而且，与控制条件相比，暴露于H2S导致K虫更频繁地出现，并在水中花费更多的时间。我们建议生理H2S耐受性和出苗行为是互补的策略。