Varsamos Stamatis, Nebel Catherine, Charmantier Guy
Equipe Adaptation Ecophysiologique et Ontogenèse, UMR 5171 UM2-IFREMER-CNRS Génome Populations Interactions Adaptation, Université Montpellier II, cc 092, Place E. Bataillon, 34095 Montpellier cedex 05, France.
Comp Biochem Physiol A Mol Integr Physiol. 2005 Aug;141(4):401-29. doi: 10.1016/j.cbpb.2005.01.013. Epub 2005 Feb 25.
Salinity and its variations are among the key factors that affect survival, metabolism and distribution during the fish development. The successful establishment of a fish species in a given habitat depends on the ability of each developmental stage to cope with salinity through osmoregulation. It is well established that adult teleosts maintain their blood osmolality close to 300 mosM kg(-1) due to ion and water regulation effected at several sites: tegument, gut, branchial chambers, urinary organs. But fewer data are available in developing fish. We propose a review on the ontogeny of osmoregulation based on studies conducted in different species. Most teleost prelarvae are able to osmoregulate at hatch, and their ability increases in later stages. Before the occurrence of gills, the prelarval tegument where a high density of ionocytes (displaying high contents of Na+/K+-ATPase) is located appears temporarily as the main osmoregulatory site. Gills develop gradually during the prelarval stage along with the numerous ionocytes they support. The tegument and gill Na+/K+-ATPase activity varies ontogenetically. During the larval phase, the osmoregulatory function shifts from the skin to the gills, which become the main osmoregulatory site. The drinking rate normalized to body weight tends to decrease throughout development. The kidney and urinary bladder develop progressively during ontogeny and the capacity to produce hypotonic urine at low salinity increases accordingly. The development of the osmoregulatory functions is hormonally controlled. These events are inter-related and are correlated with changes in salinity tolerance, which often increases markedly at the metamorphic transition from larva to juvenile. In summary, the ability of ontogenetical stages of fish to tolerate salinity through osmoregulation relies on integumental ionocytes, then digestive tract development and drinking rate, developing branchial chambers and urinary organs. The physiological changes leading to variations in salinity tolerance are one of the main basis of the ontogenetical migrations or movements between habitats of different salinity regimes.
盐度及其变化是影响鱼类发育过程中生存、代谢和分布的关键因素之一。一个鱼类物种能否在特定栖息地成功立足，取决于其各个发育阶段通过渗透调节来应对盐度的能力。众所周知，成年硬骨鱼通过在多个部位（体表、肠道、鳃腔、泌尿器官）进行离子和水分调节，使其血液渗透压维持在接近300 mosM kg(-1) 的水平。但关于发育中的鱼类，相关数据较少。我们基于对不同物种的研究，对渗透调节的个体发育进行综述。大多数硬骨鱼幼体在孵化时就能进行渗透调节，且其能力在后期会增强。在鳃出现之前，幼体体表因存在高密度的离子细胞（显示出高含量的钠钾ATP酶）而暂时成为主要的渗透调节部位。幼体阶段鳃会逐渐发育，并伴随着众多支持它们的离子细胞。体表和鳃的钠钾ATP酶活性在个体发育过程中会发生变化。在幼体期，渗透调节功能从皮肤转移到鳃，鳃成为主要的渗透调节部位。以体重标准化后的饮水率在整个发育过程中趋于下降。肾脏和膀胱在个体发育过程中逐渐发育，在低盐度下产生低渗尿液的能力也相应增加。渗透调节功能的发育受激素控制。这些事件相互关联，并与盐度耐受性的变化相关，盐度耐受性通常在从幼体到幼鱼的变态过渡阶段显著增加。总之，鱼类个体发育阶段通过渗透调节耐受盐度的能力依赖于体表离子细胞，然后是消化道发育和饮水率、发育中的鳃腔和泌尿器官。导致盐度耐受性变化的生理变化是不同盐度环境栖息地之间个体发育迁移或移动的主要基础之一。
