AEO Team (Adaptation Ecophysiologique et Ontogenèse), UMR 5119 Ecosym UM2, CNRS, IRD, Ifremer, Université Montpellier 2, Montpellier, France.
J Comp Physiol B. 2013 Jan;183(1):83-97. doi: 10.1007/s00360-012-0687-2. Epub 2012 Jul 1.
Embryonic osmoregulation effected by embryonic ionocytes in the European sea bass Dicentrarchus labrax has been studied at several sites, including the yolk sac membrane, the first gill slits and the gut ionocytes. D. labrax embryos, spawned in seawater (SW) (39 ‰), were exposed to dilute seawater (DSW) (5 ‰) during 48 h, from stage 10 pairs of somites (10S) to hatching time (HT). Control embryos originating from the same spawn were maintained in SW. Both SW and DSW embryos were examined after 24- and 48-h exposure. Nanoosmometric measurements of the embryonic fluids osmolality suggest that late embryos are confronted with the variations in external salinity and that they were able to slightly regulate their osmolality. Immunolocalization of Na⁺/K⁺ ATPase, NKCC and CFTR has shown that DSW-exposed embryos can limit ion losses due to compensatory physiological mechanisms. CFTR and NKCC were not observed in DSW embryos in the yolk sac ionocytes and in the tegumentary ionocytes of the gill slits. The quantification of mRNA indicated that NKA, NKCC1 and CFTR transcript levels increased from stage 10S to stage HT. At stage HT, following 48 h of DSW- or SW-exposure, different responses were observed according to salinity. These results, when compared to those obtained in D. labrax juveniles and adults long-term exposed to fresh water (FW), show that in embryos the physiological response following a short-term DSW exposure is different. The mechanisms of hyper-osmoregulation observed in D. labrax embryos, although not fully efficient, allow their survival for several days in DSW.
欧洲鲈鱼胚胎中的离子细胞在多个部位进行胚胎渗透调节作用的研究，包括卵黄囊膜、第一对鳃裂和肠道离子细胞。在海水中（39‰）产卵的 D. labrax 胚胎，在孵化时间（HT）前，从 10 对体节（10S）到孵化时间（HT），在稀释海水中（DSW）（5‰）中暴露 48 小时。源自同一产卵的对照胚胎在 SW 中维持。SW 和 DSW 胚胎均在暴露 24 小时和 48 小时后进行检查。胚胎液渗透压的纳米渗透压测量表明，晚期胚胎面临着外部盐度的变化，并且它们能够略微调节其渗透压。Na⁺/K⁺ATPase、NKCC 和 CFTR 的免疫定位表明，DSW 暴露的胚胎可以通过补偿生理机制限制离子丢失。在 DSW 胚胎的卵黄囊离子细胞和鳃裂的体被离子细胞中未观察到 CFTR 和 NKCC。NKA、NKCC1 和 CFTR 转录本水平从 10S 阶段到 HT 阶段增加。在 HT 阶段，在 DSW 或 SW 暴露 48 小时后，根据盐度观察到不同的反应。与在淡水（FW）中长期暴露的 D. labrax 幼体和成年鱼获得的结果相比，这些结果表明，在胚胎中，短期 DSW 暴露后的生理反应不同。在 D. labrax 胚胎中观察到的高渗调节机制虽然不完全有效，但允许它们在 DSW 中存活数天。
