Effects of temperature, photoperiod, and light intensity on the eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae

Eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae from Badrinath (altitude 5123 m) was temperature-dependent and at 21°C, it was entrained by cycles of 12 h light: 12 h darkness (LD 12:12) and free-ran in constant darkness, however, it was arrhythmic at 13°C or 17°C under identical experimental conditions (Khare, P. V., Barnabas, R. J., Kanojiya, M., Kulkarni, A. D., Joshi, D. S. (2002). Temperature dependent eclosion rhythmicity in the high altitude Himalayan strains of Drosophila ananassae. Chronobiol. Int. 19:1041-1052). The present studies were designed to see whether or not these strains could be entrained at 13°C, 17°C, and 21°C by two types of LD cycles in which the photoperiod at 100 lux intensity varied from 6 h to 18 h, and the light intensity of LD 14:10 cycles varied from 0.001 lux to 1000 lux. All LD cycles entrained this strain at 21°C but not at 13°C or 17°C. These results demonstrate that the entrainment of eclosion rhythm depends on the ambient temperature and not on the photoperiod or light intensity of LD cycles. Thus the temperature has taken precedence over the light in the entrainment process of eclosion rhythm of the high altitude Himalayan strain of D. ananassae. This may be the result of natural selection in response to the environmental temperature at Badrinath that resembles that of the sub-Arctic region but the photoperiod or light intensity are of the subtropical region.