Effect of estradiol on gonads development for resident form males of cherry salmon Oncorhynchus masou

Abstract

Effect of estradiol on development of gonads in resident form males of cherry salmon is investigated. The fish aged 0+ with initial weight of 3.48-10.70 g were treated with the hormone for 30 days, then reared for 8 months. Estradiol was given with pelleted food in concentration of 100 mg/kg. The gonads were examined histologically during entire period of the experiment. The control group included 184 specimens (90 females, 59 anadromous males and 35 males of resident form). The experimental group of 50 females and 48 males was taken randomly in 3.5 months after the end of hormonal exposure. The fund of germ cells in gonads of the experimental group consisted only of gonias. Males of resident form were identified in 6 and 8 months after the end of hormonal exposure, they were distinguished by both size of the testes and presence of germ cells at different stages. Portion of the males of resident form was similar in the control and experimental groups — 37.0 % and 40.7 % of total number of males, respectively.