Induced sexual maturation of the European eel Anguilla anguilla and fertilisation of the eggs

The aim of the present study was to induce sexual maturation in females of the European eel Anguilla anguilla using a protocol similar to that successful for Anguilla, japonica. Inducing maturation in the female European eel has proven difficult in the extreme, as only one research group has so far reported fertilisation with subsequent embryonic and larval development in A. anguilla. The present study performed two experiments. In experiment A, the 10 surviving females received a weekly injection with salmon pituitary extract (SPE) at a dose of 18.2 mg pituitary powder per week and fish, and in experiment 13, females were injected twice weekly and received a dose of 36.4 mg pituitary per fish and week. Only two experiment B fish had viable eggs. In both experiments, final oocyte maturation and ovulation was induced by injection of 17,20 beta-dihydroxy-4-pregnen-3-one (DHP) at about 2 mug/g body weight. Maturation time was 16-25 weeks in experiment A and 7.5-11.5 weeks in experiment B. In the final stages of oocyte maturation, female A. anguilla showed highly individual rates of oocyte development, and as injection protocol depended on oocyte development, six protocols had to be used. The only protocol which resulted in fertilisation of eggs with subsequent development of larval bodies-and in one case hatching, although delayed, of larvae-was weekly SPE injection followed ca. 40 h later by an extra SPE injection (18.2 mg pituitary powder), 10 h after which DHP was injected. (C) 2003 Elsevier Science B.V. All rights reserved.