Effects of photophase and altitude on oviposition rhythm of the himalayan strains of Drosophila ananassae

摘要

The effects of varying photophase and altitude of origin on the phase angle difference (Psi) of the circadian rhythm of oviposition during entrainment to light-dark (LD) cycles and the after effects of such photophases on the period of the free-running rhythm (tau) in constant darkness (DD) were evaluated in two Himalayan strains of Drosophila ananassae, the high-altitude (HA) strain front Badrinath (5,123 m above sea level = ASL) and the low-altitude (LA) strain front Firozpur (179 m ASL). The Psi (i.e., the hours from lights-on of the LD cycle to oviposition median) of both strains was determined in LD cycles in which the photophase at 100 lux varied from 6 to 18 h/24 h. The HA strain was entrained by all LD cycles except the one with 6 It photophase in which it was weakly rhythmic, but the LA strain was entrained by only three LD cycles with photophases of 10, 12, and 14 h, but photophases of 6, 8, 16, and 18 11 rendered it arrhythmic. Lights-off transition of LD cycles was the phase-determining signal for both strains as oviposition medians of the HA strain occurred similar to 6 It prior to lights-off while those of the LA strain occurred similar to 1 h after lights-off. The IV of the HA strain increased front similar to 2 h in 8 h photophase to similar to 11 h in 18 h photophase, while that of the LA strain increased from similar to 11 h in 10 h photophase to similar to 15 h in 14 h photophase. The aftereffects of photophase of the prior entraining LD cycles on tau in DD were determined by transferring flies from I-D cycles to DD. The tau of the HA strain increased from similar to 19 to similar to 25 h when transferred to DD from LD 8:16 and LD 18:6 cycles, respectively, whereas the tau of the LA strain increased from similar to 26 to similar to 28 h when transferred to DD from LD 10 : 14 and LD 14 : 10 cycles, respectively. Thus, these results demonstrate that the photophases of entraining LD cycles and the altitude of origin affected several parameters of entrainment and the period of the free-running rhythm of these strains.