| Author | Yang, Yi |
| Call Number | AIT Thesis no. AE-92-32 |
| Subject(s) | 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 |
| Abstract | The present study dealt with the determination of the
effect of juvenile immersion in solutions of 17a- methyltestosterone (MT) for different durations and at different
ages, and the determination of the critical period of sexual
differentiation of Oreochromis niloticus by inference. The
results indicated that fish growth in terms of mean individual
fish weight and specific growth rates were not significantly
different between all treatments during Phase I (p > 0.05) and
were positively correlated to male percentages of treatments (p
< 0.001 , r = 0.68, n = 20 and p < 0.05, r = 0.73, n = 20,
respectively) during Phase II, and food conversion ratios were
highly positively and negatively correlated to male percentages
of male during Phase I (p < 0 . 001, r = 0.71, n = 20) and Phase
II (p < 0.05, r = - 0.48, n = 20), respectively. Fish survival
rates did not significantly vary amongst treatments (p > 0.05)
and were not significantly correlated to male percentages (p >
0 .05 ) during the period of 17u-methyltestosterone treatment and
in subsequent culture. Control-I (MT/DMSO-free ), control-II (MT-free) and three MT-treatments starting from the 6th day to the
15th day and 30th day after hatching and starting from the 15th
day to the 18th day after hatching had sex ratios that did not
differ significant l y from the expected 50:50 mal e to female
ratio (p > 0.05, Ch i -square ). Sex ratios of a ll other treatments
including the treatment fed MT-feed were significantly different
from the expected 50:50 male to femael ratio (p < 0.0 5, Chi- square). The treatments with highest male percentages were 24-30
starting from the 24t h day to the 30th day ( 893), 21-24 (893),
21-30 (903), 24-27 (923), 21-27 (943 ) and 27-30 (943 ). This
indicated that the starting time of administration of 17umethyltestosterone had crucial effect on the success of sex
reversal. It can be concluded that the most labile period of
sexual differentiation of Oreochromis niloticus appeared to be
between the 21st day and the 30th day after hatching . The
present study indicated that the treatments starting during the
most 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 authors. |
| Year | 1992 |
| 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 Food Engineering (AE) |
| Chairperson(s) | Little, David C.; |
| Examination Committee(s) | Yakupitiyage, Amararatne ;Phillips, Michael J. |
| Scholarship Donor(s) | The Government of Federal Republic of
Germany (DAAD); |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1992 |