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 (473Kb)
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14,842,000 Yen (FY1995 5,075,000 Yen)
Effect of exposure with low pH and Al on early developmental stage of Koi was observed from fertilized egg for 40 days. Low concentration of Al, 50 ppb in rearing water might bring significant large mortality at pH 5.5 for 4 days and at pH 6.0, not so low pH, for 19 days. An aftereffect was not observed in the growth and survival rate of acid exposured survivors of Koi or pond smelt. Spowing of medaka stopped under the water pH below 3.9,at that pH some death happened but normal spowing continued under the pH above 4,1,at that pH no death happened. Spowning and ovulation of Ayu were disturbed below pH 5.2. There was a difference between males and females of Medaka in resistance against acid exposure and the females showed higher ability of osmoregulation than the males. Mature male and female rainbow trout were treated with low pH(Av. 4.5) sulfuric acid water for 1 or 2 weeks. Percentage of eyed embryos in eggs from control, 1-week-treated and 2-week-treated females were 100%, 80% and 0%, respectively. Low pH exposure of male trout induced 11% deformation in embryos fertilized with their sperm. In female fish, egg contents of 17α20β-dihydroxy-4-pregnen-3-0ne, which induces oocyte maturation, were significantly lower in low pH exposed groups. Acidified male fish showed higher plasma levels of the spermiation inducing hormone, 11-ketotestosterone. Effects on eggs were manifested under pH lower than 5.The effects on the oocyte were observed in adult female sockeye salmon which were exposed to acidic condition for more than 1 week before the timing of ovulation. These results suggest that acid stress affects the endocrinological mechanisms of final maturation in fish gametocytes.
Acidification,Salmon,Carp, Gametogenesis, embryo development, sex steroids