Selection of strains and improvement of reproduction of frogs through biotechnology methods

Reproductive biology, the breeding, growth and feeding of three species of frogs; namely Rana tigerina, Rana catesbeiana and Rana blythii were studied for the purposes of increasing reproduction, enhancing growth as well as the improvement of the culturing methods. Developmentally, the offsprings of R. tigerina reached full sexual maturity at one year old while the offsprings of R. catesbeiana studied up to 14 months were still immature. R. blythii offsprings are the slowest to reach sexual maturity. By one year old the structure of both ovary and testis still appeared similar to those of the young frogs. The number and distribution of cells in the pituitary gland was similar among all three species of frogs during the breeding and non-breeding seasons. During the breeding season the number of basophil cells in the pituitary gland were significantly increase while the number of acidophil cell did not change throughout the year. This observation showed good correlation with the changes of both ovary and testis since the ovary during the breeding season also contained more than 20 percent of mature eggs (stage VI) while the testis was full of spermatozoa. During the breeding season ovulation and spermiation could be enhanced by priming the brooders with gonadotropin releasing hormone (GnRH). The ovulation occurred within 8-12 hours after GnRH (25 micro g/Kg) administration with the percentages of success at 61.7, 37.2 and 50 in R. tigerina, R. catesbeiana and R. blythii, respectively. The spermiation could also be obtained within 1 hour after GnRH (10 micro g/Kg) injection with the percentages of success at 80, 72 and 76. The effect of GnRH stimulation on the quantity of sperm being released are (2.3 +- 0.90) * 10*[5), (2.3 +- 0.94) * 10*[5) and (2.1 +- 0.50) * 10*[5) sperms/ ml of R. tigerina, R. catesbeiana and R. blythii, respectively. The quantity of aspirated sperm was significantly decrease after 3 hours following the treatment. The mating of 3 species, R. tigerina, R. catesbeiana and R. blythii could be successfully done under natural condition. The eggs were able to develop and become froglets at room temperature (25-30 deg C) within 32, 65 and 60 days in R.tigerina, R. catesbeiana and R. blythii, respectively. The "artificial insemination" had been performed after collecting the eggs and sperms from both female and male brooders primed with GnRH or pituitary extract. The development from eggs to froglets could be obtained at about 25 days which was quicker than in the natural development. The appropriate diet or pelleted feeds were also developed for the frog culture. A variety of feeds were used to determine the growth and mortality rates of tadpoles and froglets. The tadpoles of R. tigerina and R. catesbeiana which had been fed with 50 percent protein pelleted feed showed the most rapid growth rate while the froglets showed rapid growth after being fed with 40 percent protein pelleted feed. In contrast, R. blythii could not adapt themselves to eat the pelleted feed except for the tadpole stage.