Theses and Dissertations


Title: The use of synthetic androgens for the production of monosex male Tilapia aurea (Steindachner)

Name: Guerrero III, Rafael Dineros

Degree: PhD

Chair: Dr. W.L. Shelton

Resides: FAA Library

University: Auburn

Location: Auburn, Alabama

Date: 1974

Pages: 112

Keywords: Synthetic Androgens,Monosex Male,Tilapia aurea (Steindachner).

Abstract:

Feeding of 1-dehydrotestosterone acetate (DHT), ethisterone (ET), and 17alpha-methyltestosterone (MT) at various dosage levels, for 18 and 21 days in tanks, neither affected survival nor altered growth of fry. No difference in post-treatment survival of androgen-treated and untreated fish reared in plastic pools for 120 days was observed. Significantly higher weights of some androgen-treated groups compared with that of the control were found. Treatment with ET and MT at all dosage levels resulted in significantly higher percentages of males compared with the control. One hundred percent males was produced with ET at 60 ?g/g diet. A relationship between percentage of males and total weight of fish in plastic pools was found. This suggested that increased growth of androgen-treated fish was partly due to high percentage of faster-growing males. Degeneration of testes was observed with treatment of MT at 60 ?g/g diet. No ovotestis condition was found. Sex ratios of the progenies of three ET-treated and six MT-treated males individually bred with untreated females ranged from 2 to 3.1 females:1 male. These were significantly different from the expected 1:1 ratio of sexes and indicated that sex reversal of genetic females had been achieved. Heterogamety of female T. aurea was established. Varying durations of ET and MT treatments indicated that treatment should commence when fry are 11 mm or less in total length and should continue until they are 19 mm (with ET) or 22 mm (with MT) to achieve sex reversal. ET-treated fish had higher mean total yield, attributed to high survival and high percentage of males, than the control in earthen ponds. Nest-building activities of control and ET-treated fish were comparable.

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