Observations of initial water ingestion and ion absorption in the digestive tract of Japanese eel larvae
Observations of initial water ingestion and ion absorption in the digestive tract of Japanese eel larvae
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DOI：
10.1007/s12562-014-0841-8
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发表时间：
2015-03-01
影响因子：
1.9
通讯作者：
Kaneko, Toyoji
中科院分区：
文献类型：
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作者：
Ahn, Hyojin;Lee, Kyung Mi;Kaneko, Toyoji
在日本鳗鲡的早期生活阶段，研究了海水适应性调节的启动。通过使用荧光葡聚糖作为惰性标记物在消化道中检测摄入的海水。摄食的海水在孵化后0天和1天仍停留在消化道的前部，但在2天到达肛门。扫描电子显微镜观察表明，口部在0 dph时呈狭缝状，在2 dph时发育成孔状。Na+、K+和2Cl（-）协同转运蛋白2 β（NKCC 2 β）和Na+和Cl-协同转运蛋白β（NCC β）mRNA的表达主要分别在肠和直肠中检测到。这些结果与成年鳗鱼的结果一致，表明肠道和直肠也是仔鳗吸收活性离子的部位。NKCC 2 β的表达水平从4 dph急剧增加到6 dph，而NCC β水平在孵化当天最高，可能是由于母体因素。NCC β的表达水平在3-4 dph时下降，然后在7 dph时增加至恒定状态。我们的研究结果证实，早在孵化当天就开始调节，并在一周内稳定下来。
The onset of osmoregulation for seawater adaptation was examined during the early life stages of the Japanese eel. Ingested seawater was detected in the digestive tract by using fluorescent dextran as an inert marker. Ingested seawater remained in the forepart of the digestive tract at 0 and 1 days post hatching (dph), but reached the anus at 2 dph. Scanning electron microscope observations showed that the mouth appeared as a slit at 0 dph and developed into a hole-like shape at 2 dph. Expressions of Na+, K+, and 2Cl(-) cotransporter 2 beta (NKCC2 beta), and Na+ and Cl- cotransporter beta (NCC beta) mRNAs were detected mainly in the intestine and rectum, respectively. These results are consistent with those of the adult eel, suggesting that the intestine and rectum are the sites of active ion absorption in larvae also. Expression levels of NKCC2 beta steeply increased from 4 to 6 dph, while NCC beta levels were highest on the day of hatching, presumably due to a maternal factor. The expression levels of NCC beta decreased by 3-4 dph and then increased to a constant status at 7 dph. Our findings confirmed that osmoregulation started as early as the day of hatching and stabilized within a week.