Influence of incubation temperature and substrate on eggs and embryos of the garden lizard, Calotes versicolor (Daud.)

Abstract

The influence of incubation temperature and substrate on hatching success, duration of incubation and hatchlings' traits in Calotes versicolor was studied experimentally. The eggs were incubated in soil at 1) ambient (27°C ± 2 s), 2) ambient temperature and exposed to 35°C for 1 or 3hrs/day, 3) constant 30°C, 33°C and 35°C. In another experiment soil, sand or cotton wool was used as incubation substrate at ambient temperature. Duration of incubation was inversely related to incubation temperature. Hatching success was high at ambient (93%), at 30°C (89%) and for eggs exposed to 1 hr (94%) or 3 hr/day to 35°C (93%) compared to those at 33°C (59%) and 35°C (53%). Egg mass increased until hatching, but with a temporal difference in the gain at different temperatures. At high temperatures, it increased rapidly. Eggs incubated at ambient temperature and 1 or 3 hrs exposure to 35°C produced hatchlings heavier than their sibs that hatched at 30°C, 33°C or 35°C. Smaller size of hatchlings at higher incubation temperatures was due to early hatching and low utilization of yolk. Incubation substrate had no influence on offspring traits but hatching success was low (84 ± 9%) in cotton wool. Thus, incubation of eggs in soil or sand at ambient temperature with a periodic exposure to high tolerable temperature provides an optimum balance between developmental rate, hatching success and hatchling quality in C. versicolor.