Sundell Kristina, Wrange Anna-Lisa, Jonsson Per R, Blomberg Anders
Department of Biological and Environmental Sciences and Swedish Mariculture Research Center (SWEMARC), University of Gothenburg, Gothenburg, Sweden.
IVL Swedish Environmental Research Institute, Fiskebäckskil, Sweden.
Front Physiol. 2019 Aug 21;10:877. doi: 10.3389/fphys.2019.00877. eCollection 2019.
Barnacles form a globally ubiquitous group of sessile crustaceans that are particularly common in the coastal intertidal. Several barnacle species are described as highly euryhaline and a few species even have the ability to colonize estuarine and brackish habitats below 5 PSU. However, the physiological and/or morphological adaptations that allow barnacles to live at low salinities are poorly understood and current knowledge is largely based on classical eco-physiological studies offering limited insight into the molecular mechanisms. This review provides an overview of available knowledge of salinity tolerance in barnacles and what is currently known about their osmoregulatory strategies. To stimulate future studies on barnacle euryhalinity, we briefly review and compare barnacles to other marine invertebrates with known mechanisms of osmoregulation with focus on crustaceans. Different mechanisms are described based on the current understanding of molecular biology and integrative physiology of osmoregulation. We focus on ion and water transport across epithelial cell layers, including transport mechanisms across cell membranes and paracellular transfer across tight junctions as well as on the use of intra- and extracellular osmolytes. Based on this current knowledge, we discuss the osmoregulatory mechanisms possibly present in barnacles. We further discuss evolutionary consequences of barnacle osmoregulation including invasion-success in new habitats and life-history evolution. Tolerance to low salinities may play a crucial role in determining future distributions of barnacles since forthcoming climate-change scenarios predict decreased salinity in shallow coastal areas. Finally, we outline future research directions to identify osmoregulatory tissues, characterize physiological and molecular mechanisms, and explore ecological and evolutionary implications of osmoregulation in barnacles.
藤壶是一类在全球广泛分布的固着性甲壳动物，在沿海潮间带尤为常见。有几种藤壶物种被描述为广盐性很强，甚至有一些物种能够在盐度低于5个实用盐度单位（PSU）的河口和微咸水栖息地定殖。然而，藤壶能够在低盐度环境中生存的生理和/或形态适应机制却鲜为人知，目前的知识主要基于经典的生态生理学研究，对分子机制的洞察有限。本综述概述了藤壶耐盐性的现有知识以及它们目前已知的渗透调节策略。为了激发未来对藤壶广盐性的研究，我们简要回顾并将藤壶与其他具有已知渗透调节机制的海洋无脊椎动物进行比较，重点是甲壳类动物。基于目前对渗透调节分子生物学和整合生理学的理解，描述了不同的机制。我们关注离子和水跨上皮细胞层的运输，包括跨细胞膜的运输机制和通过紧密连接的细胞旁转运，以及细胞内和细胞外渗透剂的使用。基于当前的这些知识，我们讨论了藤壶可能存在的渗透调节机制。我们进一步讨论了藤壶渗透调节的进化后果，包括在新栖息地的入侵成功和生活史进化。耐低盐度可能在决定藤壶未来分布方面起着关键作用，因为即将到来的气候变化情景预测浅海沿岸地区盐度会降低。最后，我们概述了未来的研究方向，以确定渗透调节组织，表征生理和分子机制，并探索藤壶渗透调节的生态和进化意义。
