Barrios-Figueroa R, Urbina M A
Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Chile.
Doctorado en Sistemática y Biodiversidad, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, 4030000, Chile.
Conserv Physiol. 2023 Jan 28;11(1):coac089. doi: 10.1093/conphys/coac089. eCollection 2023.
Salinization is of global concern, threatening freshwater biodiversity. Salinity tolerance is highly variable and therefore needs to be evaluated on a species-specific basis. An estuarine population of a freshwater gastropod endemic to Chile and classified as vulnerable, has been recently found in the Biobío River's mouth, suggesting some degree of tolerance to brackish waters. This study evaluated the survival, behaviour (medium preference) and physiology of when exposed to salinities higher than freshwater, thus elucidating the potential mechanisms used to survive salinization. belongs to the Pulmonate group;, so we evaluated oxygen uptake in air and water, aiming to evaluate emersion as a potential avoidance response to a progressive salinity increase. Complete embryo development was observed for salinities ≤ 16 PSU (practical salinity units) but hatching rates above 50% were only achieved in freshwater (0 PSU). It was also found that salinity had stage-specific effects during embryonic development. In adults, acute exposure to brackish water (12 PSU) caused a decrease in oxygen consumption (compared to freshwater), in the ammonium excretion rates and in the percentage of muscular water content. Although was able to take up oxygen in both mediums, survival in air decreased over time (days), which correlates with the behavioural preference to remain submerged, even at elevated salinities. Considering the survival of adults and embryos decreased as salinity increased and the lack of an avoidance behaviour or a physiological ability to maintain homeostasis at salinities higher than freshwater, our results suggest this snail could be adversely affected by salinization in the long term. Furthermore, given the ability of to uptake oxygen in both mediums, it should be considered as a facultative air breather snail, rather than a strictly aquatic species.
盐渍化是全球关注的问题，威胁着淡水生物多样性。耐盐性差异很大，因此需要根据物种特异性进行评估。最近在比奥比奥河河口发现了一种智利特有的淡水腹足动物的河口种群，该种群被列为易危物种，这表明其对微咸水有一定程度的耐受性。本研究评估了该物种在暴露于高于淡水盐度的环境时的生存、行为（介质偏好）和生理状况，从而阐明其在盐渍化环境中生存所采用的潜在机制。该物种属于肺螺亚纲；因此，我们评估了其在空气和水中的氧气摄取情况，旨在评估其作为对盐度逐渐升高的潜在回避反应的浮出水面行为。在盐度≤16 PSU（实用盐度单位）时观察到胚胎完全发育，但只有在淡水（0 PSU）中孵化率才超过50%。还发现盐度在胚胎发育过程中具有阶段特异性影响。在成体中，急性暴露于微咸水（12 PSU）会导致氧气消耗（与淡水相比）、铵排泄率和肌肉含水量百分比降低。尽管该物种在两种介质中都能摄取氧气，但在空气中的生存时间会随着时间（天数）的推移而减少，这与即使在盐度升高时仍倾向于保持浸没的行为偏好相关。考虑到随着盐度升高成体和胚胎的存活率降低，以及在高于淡水盐度时缺乏回避行为或维持体内平衡的生理能力，我们的结果表明，从长期来看，这种蜗牛可能会受到盐渍化的不利影响。此外，鉴于该物种在两种介质中都能摄取氧气的能力，应将其视为兼性空气呼吸蜗牛，而不是严格的水生物种。
