ATTEMPTS TO INDUCE EXPERIMENTALLY MATURATION OF THE GONADS OF THE EUROPEAN EEL, ANGUILLA ANGUILLA L.

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Abstract
In the introduction a brief account is given of all that is known regarding the sexual biology of the European eel. The authors'' own expts. comprise 7 male and 99 female silver eels. Intraperitoneal injections of chorionic gonadotropin (Physex Leo, 400-800 I.U., spread over 8-20 weeks) produced full spermatogenesis in 3 of the male silver eels, and a distinct although less pronounced effect in the remaining 4. The female silver eels were treated either with Physex alone (total dose up to 11,500 I.U. in the course of 3-21 weeks) or Physex + 4,4-dihydroxyphenyl- [gamma]-[delta]-n-hexane (Hexoestrol, A.B.) the total dose varying between 1500 I.U. of Physex + 3 mg. of Hexoestrol and 12500 I.U. of Physex + 25 mg. of Hexoestrol, spread over 3-42 weeks. The combined treatment was the more efficient and it was possible to obtain a growth of the eggs up to a diameter of 0.50 mm. (controls: 0.12-0.18 mm.). The experimentally produced large eggs (exceeding 0.35 mm.) were loosely attached to the ovary, a sign of approaching maturity. A positive correlation was observed between the dose of hormone and the effect. In the combined treatment larger intervals between the injections led to a more marked effect than did the shorter intervals.

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