Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA.
Proc Biol Sci. 2022 Jul 27;289(1979):20220529. doi: 10.1098/rspb.2022.0529.
Relative to a growing body of knowledge about the negative consequences of freshwater salinization, little is known about how aquatic insects respond to progressively ion-poor conditions. Here, we examined life-history and physiological acclimation in by rearing nymphs from 1-day post-egg hatch to adulthood across a gradient of decreasing Na concentrations (15, 8, 4, 2 and 1 mg l Na). We found no significant changes in survival, growth, development time and whole-body Na content across these treatments. Radiotracer data revealed that nymphs acclimated to their dilute exposures by increasing their rates of Na uptake and were able to maintain a relatively narrow range of uptake rates (±s.e.m.) of 38.5 ± 4.2 µg Na g h across all treatments. By contrast, the Na uptake rates observed in naive nymphs were much more concentration dependent. This acclimatory response is partially explained by differences in ionocyte counts on the gills of nymphs reared under different salinities. Acclimated nymphs were surprisingly less retentive of their sodium composition when subjected to deionized water challenge. By contrasting our findings with a previous salinity acclimation study, we show a physiological affinity for dilute conditions in this emerging mayfly model.
相对于大量关于淡水盐化负面影响的知识，人们对水生昆虫如何应对逐渐贫化的离子条件知之甚少。在这里，我们通过在逐渐降低的 Na 浓度梯度（15、8、4、2 和 1 mg l Na）下从孵化后 1 天的若虫到成虫来饲养若虫，研究了生活史和生理适应。我们发现，在这些处理中，存活率、生长、发育时间和全身体 Na 含量均无显著变化。示踪剂数据显示，若虫通过增加 Na 摄取率来适应其稀释暴露，并能够维持相对较窄的摄取率范围（±s.e.m.），在所有处理中均为 38.5 ± 4.2 µg Na g h。相比之下，在未适应的若虫中观察到的 Na 摄取率受浓度的影响更大。这种适应反应部分解释了在不同盐度下饲养的若虫鳃上的离子细胞计数的差异。当受到去离子水挑战时，适应的若虫出人意料地保留较少的钠成分。通过将我们的发现与之前的 盐度适应研究进行对比，我们展示了这个新兴的蜉蝣模型对低浓度条件的生理亲和力。
