Biology Department, Southern Connecticut State University, New Haven, CT, 06515, USA.
Center for Nanotechnology, Connecticut State Colleges and Universities, New Haven, CT, 06515, USA.
Environ Pollut. 2022 Jan 1;292(Pt B):118441. doi: 10.1016/j.envpol.2021.118441. Epub 2021 Oct 30.
Across the planet, winter de-icing practices have caused secondary salinization of freshwater habitats. Many amphibians are vulnerable because of permeable skin and reliance on small ponds, where salinity can be high. Early developmental stages of amphibians are especially sensitive to salt, and larvae developing in salt-polluted environments must osmoregulate through ion exchange in gills. Though ionoregulation in amphibian gills is generally understood, the role of gill morphology remains poorly described. Yet gill structure should affect ionoregulatory capacity, for instance in terms of available surface area. As larval amphibian gills also play critical roles in gas exchange and foraging, changes in gill morphology from salt pollution potentially affect not only osmoregulation, but also respiration and feeding. Here, we used an exposure experiment to quantify salinity effects on larval gill morphology in wood frogs (Rana sylvatica). We measured a suite of morphological traits on gill tufts-where ionoregulation and gas exchange occur-and on gill filters used in feeding. Larvae raised in elevated salinity developed larger gill tufts but with lower surface area to volume ratio. Epithelial cells on these tufts were less circular but occurred at higher densities. Gill filters showed increased spacing, likely reducing feeding efficiency. Many morphological gill traits responded quadratically, suggesting that salinity might induce plasticity in gills at intermediate concentrations until energetic demands exceed plasticity. Together, these changes likely diminish ionoregulatory and respiratory functionality of gill tufts, and compromise feeding functionality of gill filters. Thus, a singular change in aquatic environment from a widespread pollutant appears to generate a suite of consequences via changes in gill morphology. Critically, these changes in traits likely compound the severity of fitness impacts in populations dwelling in salinized environments, whereby ionoregulatory energetic demands should increase respiratory and foraging demands, but in individuals who possess structures poorly adapted for these functions.
在全球范围内，冬季除冰做法导致了淡水栖息地的次生盐化。许多两栖动物很脆弱，因为它们的皮肤具有渗透性，并且依赖于盐分可能很高的小池塘。两栖动物的早期发育阶段对盐分特别敏感，在受盐分污染的环境中发育的幼虫必须通过鳃中的离子交换来调节渗透压。尽管两栖动物鳃中的离子调节一般为人所知，但鳃形态的作用仍描述不足。然而，鳃结构应该影响离子调节能力，例如在可用表面积方面。由于幼蛙的鳃在气体交换和觅食中也起着关键作用，因此盐污染引起的鳃形态变化不仅可能影响渗透压，还可能影响呼吸和进食。在这里，我们使用暴露实验来量化盐度对林蛙（Rana sylvatica）幼虫鳃形态的影响。我们测量了鳃簇——离子调节和气体交换发生的地方——以及用于进食的鳃过滤器的一系列形态特征。在高盐度下饲养的幼虫发育出更大的鳃簇，但表面积与体积比降低。这些簇上的上皮细胞不太圆，但密度更高。鳃过滤器的间距增加，可能降低了进食效率。许多形态鳃特征呈二次曲线响应，表明盐度可能在中间浓度下诱导鳃的可塑性，直到能量需求超过可塑性。总的来说，这些变化可能会降低鳃簇的离子调节和呼吸功能，并损害鳃过滤器的进食功能。因此，水生环境中单一污染物的变化似乎会通过鳃形态的变化产生一系列后果。至关重要的是，这些特征的变化可能会加剧生活在盐化环境中的种群的适应力影响的严重程度，其中离子调节的能量需求应该增加呼吸和觅食需求，但对于那些拥有结构不太适应这些功能的个体而言。
