FURTHER ATTEMPTS TO INDUCE MATURATION OF THE EGGS OF THE EUROPEAN EEL, ANGUILLA ANGUILLA L., BY HORMONE INJECTIONS

Abstract

Various hormones were used with a variety of dosage and time schedules to determine the effect on size of eggs of the European eel. The maximal egg diameter reached in eels injected every 2-3 weeks with 500 I.U. of chorionic gonadotropin (Physex Leo) and 1 mg diparaoxyphenylhexane (Hexoestrol) was about 0.34 mm. Divided hormone doses administered more frequently or doubling the hormone dose at each injection did not increase the egg size further. Substituting estradiol dipropionate obtained from the urine of pregnant mares for the synthetic Hexoestrol led to approximately the same maximal egg size. An intramuscular injection of progesterone in addition to weekly injections of 175 I.U. of Physex resulted in a maximal egg diameter of 28 mm.