Groups of about 300 elvers, 7 cm long, were reared at the Aquaculture Experimental Station of the ENEL (Italian National Agency for Electric Power, la Casella), in 300 1 tanks with flowing fresh water at 24°C and fed with a commercial pelleted diet to which was added (1) methyltestosterone (0.001 g per kg of dry diet), (2) ethynilestradiol (0.01 g per kg). After 6 months all groups were fed only with commercial diet. After 3 and 6 months from the beginning of the treatments, thè gonads of samples of the 5 largest eels of each group were fixed, embedded in Epon-Araldite mixture and examined by optical micro¬scope; after 10 months the gonads of samples of 15 eels, stratified for total length, within the range between 11 and 25 cm, were examined on semithin sections. In the control group, the examined eels showed undifferentiated gonads in different stages in re-lation to body growth; only one, 25 cm long, had a testis-like gonad with gonoduct. In the methyltestosterone treated group two types of gonad were found: 1) undifferentiated ones, similar to the control; 2) gonads with few germ cells and with hypertrophied connective tissue. Among the ethynilestradiol treated eels some ones, with a total length less than 15 cm, had a gonadic lamina full of postpackytene oocytes. All the examined eels (15) longer than 15 cm had a differentiated ovary with previtellogenic and early vitellogenic oocytes. The results of these experiments) show that, when given at an early developmental stage, sex steroids affected the sexual differentiation of thè eel gonad: estradici induced thè differentiation of an ovary and stimulated the oocyte growth. Meth¬yltestosterone produced a degeneration of a large part of the germ cells with an abnormally structured gonad
Tentativo di inversione sessuale in Anguilla anguilla medainte trattamenti ormonali.II. Ottimizzazione delle metodologie di controllo biologico. The effects of sex steroids on gonad sex differentiation
GRANDI, Gilberto;COLOMBO, Giuseppe
1991
Abstract
Groups of about 300 elvers, 7 cm long, were reared at the Aquaculture Experimental Station of the ENEL (Italian National Agency for Electric Power, la Casella), in 300 1 tanks with flowing fresh water at 24°C and fed with a commercial pelleted diet to which was added (1) methyltestosterone (0.001 g per kg of dry diet), (2) ethynilestradiol (0.01 g per kg). After 6 months all groups were fed only with commercial diet. After 3 and 6 months from the beginning of the treatments, thè gonads of samples of the 5 largest eels of each group were fixed, embedded in Epon-Araldite mixture and examined by optical micro¬scope; after 10 months the gonads of samples of 15 eels, stratified for total length, within the range between 11 and 25 cm, were examined on semithin sections. In the control group, the examined eels showed undifferentiated gonads in different stages in re-lation to body growth; only one, 25 cm long, had a testis-like gonad with gonoduct. In the methyltestosterone treated group two types of gonad were found: 1) undifferentiated ones, similar to the control; 2) gonads with few germ cells and with hypertrophied connective tissue. Among the ethynilestradiol treated eels some ones, with a total length less than 15 cm, had a gonadic lamina full of postpackytene oocytes. All the examined eels (15) longer than 15 cm had a differentiated ovary with previtellogenic and early vitellogenic oocytes. The results of these experiments) show that, when given at an early developmental stage, sex steroids affected the sexual differentiation of thè eel gonad: estradici induced thè differentiation of an ovary and stimulated the oocyte growth. Meth¬yltestosterone produced a degeneration of a large part of the germ cells with an abnormally structured gonadI documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
