Effects of immersion of larvae in oestradiol-17ß on feminization, structural changes of gonad and growth performance in the Far Eastern catfish Silurus asotus (Linnaeus)
D.S.Kim, H.J. Cho, I.C. Bang, G.C.Choi, Y.K. Nam-2001

Aquaculture Research, 32(5): 323-328

Abstract:

Immersion of 1-day-old Silurus asotus (Linnaeus) larvae in 50, 100 or 200 mg L^-1 oestradiol-17ß for 15 days altered gonad differentiation and gonadal morphology. The survival of the group immersed at the highest dose (200 mg L^-1) was reduced significantly (86%), whereas survival of the groups immersed at the lower doses was as high as that of untreated controls (94%). The sex ratio of the untreated group was close to 1:1 (female–male); however, the incidence of females was significantly higher in groups immersed in doses of 50, 100 and 200 mg L^-1, i.e. 86%, 92% and 99.4%, respectively. Ovarian morphology of feminized individuals was different to that of the controls; the ovary was morphologically rather similar to testis although it contained fully matured oocytes. Morphological changes in genital organs were also noted in fish exposed to oestradiol-17ß the shape and size of genital papilla were intermediate between those of normal male and female. During a 4-month growth trial after the exposure, the feminized fish showed significantly improved growth performance over normal genetic males (P <0.05), although the growth was not equal to that of normal genetic females (P < 0.05).

(Department of Aquaculture, Pukyong National University, Pusan 608-737, South Korea)

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