Occurrence of larval and adult types of ion-secreting ionocytes in Japanese eel Anguilla japonica
Occurrence of larval and adult types of ion-secreting ionocytes in Japanese eel Anguilla japonica
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日本鳗鱼幼虫和成虫离子分泌离子细胞的出现
DOI：
10.1007/s10228-015-0463-x
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发表时间：
2015
影响因子：
1.2
通讯作者：
Soichi Watanabe and Toyoji Kaneko
中科院分区：
文献类型：
--
作者：
Seo Miyoung;Mari Kuroki;Akihiro Okamura;Katsumi Tsukamoto;Soichi Watanabe and Toyoji Kaneko
鳗鱼是在海洋和淡水栖息地之间迁徙的浅水性鱼类。鳗鱼幼体在海洋中长达数千公里的漫长迁徙对它们的招募成功至关重要。海洋中的细头鳗具有与河流中的玻璃鳗和黄鳗的海底生活方式完全不同的远洋生活方式。众所周知，鳗鱼的体表存在离子细胞，可能在体内环境中维持离子和渗透状态；然而，离子细胞的详细形态和功能仍不清楚。在本研究中，我们的目的是：1)阐明高渗条件下养殖的鳗鱼脑皮层的形态特征；2)研究鳗鱼和黄鳗的离子细胞的离子转运功能。Na+/K+-ATPase免疫反应离子细胞分布于小头节的整个体表。离子细胞通过其位于路面细胞边界的顶膜与外界环境接触。海水驯化黄鳗皮肤中未见Na+/K+-ATPase免疫阳性细胞。在幼虫皮肤的离子细胞中，顶膜呈微绒毛样微突起的圆盘状。同时，黄鳗鳃离子细胞顶膜呈凹面。与黄鳗的鳃相比，细头鳗的离子细胞线粒体增大，管状系统发达。小脑离子细胞在其顶端呈CFTR免疫反应，在基底外侧区呈NKCC1免疫反应，提示皮肤离子细胞参与了盐的分泌。这些结果支持日本鳗在早期生命阶段通过皮肤离子细胞维持离子平衡的观点，以及在黄鳗阶段形成功能性鳃和鳃离子细胞后，细头鳗皮肤离子细胞消失的观点。
The anguillid eels are catadromous fishes that migrate between marine and freshwater habitats. The long migration of eel larvae, called leptocephali, as long as thousands of kilometers in the ocean is important to determine their recruitment successes. The leptocephali in the ocean have a pelagic lifestyle totally different from the benthic one of glass eels and yellow eels in rivers. It is known that eel leptocephali have ionocytes on the body surface that may maintain ionic and osmotic status in the internal environment; however, detailed morphology and function of ionocytes in leptocephali are still unknown. In the present study, we aimed 1) to clarify the morphological features of the epidermis in Japanese eelAnguilla japonicaleptocephali cultured in hyper-osmotic condition, and 2) to examine the ion-transporting functions of ionocytes of both leptocephali and yellow eels. Na+/K+-ATPase-immunoreactive ionocytes were distributed all over the body surface of leptocephali. Ionocytes were in contact with external environments through their apical membrane, which was located at the boundary of pavement cells. Na+/K+-ATPase-immunopositive cells were not observed in the skin of seawater-acclimated yellow eels. In ionocytes of the larval skin, the apical membrane appeared as a slightly projecting disk with a microvilli-like structure. Meanwhile, the apical membrane of gill ionocytes of yellow eels formed a concave surface. In ionocytes of leptocephali, mitochondria were enlarged and the tubular system was well developed, as compared with those of the gill of yellow eels. Ionocytes of leptocephali showed CFTR immunoreaction in their apical region and NKCC1 immunoreaction in their basolateral region, suggesting that the skin ionocytes are involved in salt secretion. These results support the notion that Japanese eel maintain their ion balance through skin ionocytes during early life stages, and that the skin ionocytes of leptocephali disappear in yellow eel stages after the formation of functional gills and gill ionocytes.