科研之友
微信
新浪微博
Facebook
分享链接
摘要
Sulfate (SO42-) is maintained at similar to 1 mmoll(-1) in teleost fishes that are exposed to media of varying SO42- concentrations. We first measured plasma SO42- concentration in euryhaline fishes that adapt to both SO42--poor freshwater (<0.5 mmoll(-1)) and SO42--enriched seawater (30 mmoll(-1)). Unlike Mozambique tilapia and chum salmon, Japanese eels maintained higher plasma SO42- concentration in freshwater (6.2 +/- 2.3 mmoll(-1)) than in seawater (0.7 +/- 0.1 mmoll(-1)). We then analyzed the whole-body SO42- budget using (SO42-)-S-35. (SO42-)-S-35 influx in seawater-adapted eels occurred by 84.5% via body surfaces and 15.5% via digestive tracts. The SO42- influx was higher in seawater eels (1.55 mu molkg(-1)h(-1)) than in freshwater eels (0.09 mu molkg(-1)min(-1)), but it was facilitated in freshwater eels when the difference in SO42- concentrations between plasma and environment was taken into account (freshwater eels, 6.2 vs 0.3 mmoll(-1); seawater eels, 0.7 vs 30 mmoll(-1)). One hour after injection of 35SO(4)(2-) into the blood of seawater eels, the kidney excreted similar to 97% of the ionized form, whereas the radioactivity increased gradually in the medium and the rectal fluid more than 3h after injection. As the radioactivity was poorly adsorbed by anion-exchange resin, 35SO(4)(2-) in the blood may be incorporated into cells and excreted by the intestine, gills and skin, probably as mucus. These results show that freshwater eels take up SO42- actively from the environment, but seawater eels cope with the obligatory influx of SO42- through the gills by excreting excess SO42- via the kidney and in mucus.
- 出版日期2012-5
