Effect of gibberellin-A3 on metamorphosis in the Egyptian toad Bufo regularis

The present study was carried out to study the effect of gibberellin-A3 on the metamorphosis of the Egyptian toad Bufo regularis. Samples of B. regularis were collected from Shebin El-Kom, Menoufia Governorate during the breeding season and kept in aquaria with little water till spawning, fertilized eggs are divided into 2 groups of 200 eggs each. The 1st group was treated with 5 ppm of gibberellin-A3 (Berelex) 3 days/week for the period of metamorphosis. The second group was left untreated under the same environmental conditions and considered as a control. Hatchability of the eggs in each group was recorded. External lengths of the total body, hind limbs and the tail were measured. As a measure of apoptotic DNA fragmentation, the presence of DNA ladder was determined. The results showed that out of 200 eggs 47.5% were hatched in the control group and 76.5% were hatched in gibberellin-A3 treated group. The average duration of metamorphosis was 60 days and 52 days in the control and treated groups, respectively. There was an increase in the total length of the hind limbs of the treated tadpole as compared with the control throughout the experimental periods. DNA isolated from control and tadpoles treated with gibberellin-A3 showed degradation into oligonucleotide fragments forming a clear laddering pattern of apoptosis, but the treated tadpoles showed an increase of DNA fragmentation.