Sex reversal and sex differentiation in common carp : Cyprinus carpio (Linnaeus) | |
| Author | Ahmad, Sultanul Arifin Shameem |
| Call Number | AIT Thesis no. AS-99-15 |
| Subject(s) | Carp Fishes--Sexing |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. AS-99-15 |
| Abstract | Hormonal manipulation of sex to control unwanted reproduction in prolific breeding fishes is one of the modern and popular approaches in aquaculture. Hormonal administrations in fish have been demonstrated to retard gonadal development and alter sex ratio significantly. Hormonal sex reversal in the common carp (Cyprinus carpio) may desirable for the direct production of all-male progeny or for the indirect production of all-female progeny by mating normal XX females with sex reversed XX males. Androgenic sex reversal in the common carp has been achieved by oral administration of 17a-methyltestosterone (17a-MT). However, the sex reversal technique for common carp needs further optimization. The present study dealt with the determination of the effectiveness of mode of administration of 17a-MT and androstenedione hormones to common carp fry and the efficacy of these hormones to produce functional sex reversed males. In this study attempts were made to manipulate the sex of the Cyprinus carpio by combination of immersion and oral administration, and only through oral administration of 17a-MT and androstenedione separately. In the combined method immersion were performed during the period of 4 - 50 days after hatching (a. h.) at the concentration of 1 ppm, for oral administration 51 -90 days a. h. at the rate 100 mg.kg-1 feed. Furthermore, treatment without hormone referred as control-I and to produce sterile fish using 500 mg.ki1 diet of 17a-MT through oral administration during 8-53 days a. h. referred as control-II. Control-I (no hormone) had sex ratios which did not differ significantly from the expected 1: 1 male to female ratio (P > 0.05). Sex ratios of all other treatments except combined method of 17a-MT were significantly different (P < 0.05) from the untreated Control-I. Oral administration of 100 mg.kg-1 feed androstenedione during 51-90 days produced 90.36 % males without any females, the remaining fish being probably sterile. Other treatments of androstenedione and 17a-MT resulted in higher percentages of non-males (female, intersex and sterile) especially sterile fish. This result suggested that the most effective treatment to producing sex reversed male was by the oral administration of androstenedione at 100 mg.kg-1 and furthermore that androstenedione is more efficient than 17a-MT in both methods of administration. The results also indicate that starting time of hormone administration had crucial effect on the success of sex reversal indicating that the most labile period for sex differentiation of Cyprinus carpio in between 51-90days a. h. The present study also suggested that treatment starting during more labile period of sexual differentiation was much more effective than those starting from the sexually undifferentiated stage and continuing through the stages of gonadal sexual differentiation which was suggested by Yamamoto (1969) and followed by almost all researchers in the field. Early exposure to hormones through immersion did not increase the proportion of sex reversal but rather increased the proportion of sterile individuals. Fish survival did not significantly vary amongst treatments during the whole experimental period. Fish growth in terms of mean weight were only significantly different after the treatment period with sterile fish shown to grow faster than the others fish. Attempts to histologically characterize sex differentiation of treated and control fish during and subsequent to the period of treatment failed due to delayed sexual maturation (gonads could not be identified in whole body histological sections made at days 50, 90 and 150 a. h.) possible due to poor nutrition during the early grow-out phase. However, histological analysis of gonads at 210 days a. h. showed that androgen treatments had affected gonadal development and ultrastructure in both testes and ovaries. Gonads weight and gonadosomatic index (OSI) of both male and females were lower in the fish receiving the combined method in comparison to those administered hormone orally alone and all treated fish had lower OSI than the untreated control-I. This indicated that the exposure to androgens had an inhibitory effect on gonad development correlated to the duration of exposure. In this study oral administration of 500 mg.kg-1 feed in oral administration produced 100 % sterile fish which verified the research done by Rao et al. (1990). Oral administration of androstenedione at 100 mg.kg-1 for 50-90 days a. h. is recommended for effective masculinization of common carp fry. |
| Year | 1999 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. AS-99-15 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Aquatic Systems (AS) |
| Chairperson(s) | Mair, Graham C.; |
| Examination Committee(s) | Bart, Amrit;Yakupitiyage, Amararatne; |
| Scholarship Donor(s) | Royal Thai Government; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1999 |