Table 1
Entrainment parameters of D. helvetica strains in the field
| Strain | Ψo (h) | Ψe (h) | ΨM-E (h) | α/ρ | TAPC |
| haH at NFT | 5.2 (0.4) | - 1.4 (0.5) | 0.4 (0.1) | 310 (8) | |
| haH at CT | 5.2 (0.3) | 1.1 (0.4) | 0.7 (0.2) | 601 (76) | |
| laH at NFT | - 1.2 (0.3) | 0.4 (0.3) | 5.6 (0.4) | 1.7 (0.4) | 501 (49) |
| laH at CT | - 1.1 (0.3) | 0.4 (0.2) | 2.4 (0.4) | 1.7 (0.4) | 813 (39) |
Mean values (± SD, N = 21) for the phase of activity onset (Ψo), phase of activity end (Ψe), the interval between morning and evening peaks (ΨM-E), the ratio of activity phase to rest phase (α/ρ) and the total activity per cycle (TAPC) for males of the haH strain and the laH strain of D. helvetica entrained by natural LD 14.1:9.9 cycles in the naturally fluctuating temperature (NFT) regime and in constant temperature (CT) regime (20 ± 0.5°C) at the altitude of origin in the field.
Figure 1
Activity records of representative males of the haH and laH strains of D. helvetica monitored at the breeding site of each strain in the field in natural light-dark 14.1:9.9 h cycles under NFT and CT regimes. Black portions of each time bar indicate the scotophase and the open portion indicates the photophase. SR and SS denote the sunrise and sunset, respectively, while M, N and E denote the morning, noon and evening, respectively. Onset of activity of both males of the haH strain occurred in the forenoon ~4.5 h after SR in both temperature regimes, but the end of activity of male # 211 (A) occurred ~1 h before SS in NFT regime, and that of the male # 36 (C) occurred ~1 h after SS in CT regime. Onset and end of activity in both males of the laH strain occurred ~1 h before SR and ~0.4 h after SS under both temperature regimes, but the ΨM-E of the male # 51 (E) in NFT regime was 4.8 h, while that of the male # 24 (G) was 2.2 h in CT regime. The mean entrainment activity profile of 21 males of each strain for 11 days is shown in histogram format (B, D, F, H). Males of the haH strain had a unimodal activity pattern in both temperature regimes; however, activity ended ~1 h before SS in the NFT regime (B) and ~1 h after SS in the CT regime (D). Males of the laH strain had bimodal activity patterns in both temperature regimes; however, ΨM-E was 5.2 h in NFT regime (F) and 2.3 h in the CT regime (H).
Figure 2
Curves passing through mean values (N = 22) of the natural light intensity (open circles) and environmental temperature (filled circles) obtained at the breeding site of the haH strain (A) at Hemkund-Sahib (4,121 m) and at the breeding site of the laH strain of D. helvetica (B) at Birahi (1,132 m). Data were collected from 1 to 21 July 2005 when the natural photoperiod was ~14 h. Note that light intensity curves were almost similar at both breeding sites but the temperature curves were strikingly dissimilar. Ψoand Ψe (vertical lines) denote the phase of activity onset and the phase of activity offset, respectively. The haH flies began activity ~4.5 h after sunrise (SR) when the temperature and light intensity were ~19°C and 79,000 lux, respectively, while the laH flies began activity ~1 h before sunrise when the temperature and light intensity were ~20°C and 1 lux, respectively. The haH flies terminated activity 1.4 h before sunset (SS) when temperature and light intensity were ~14°C and 17,000 lux, respectively, while the laH flies terminated activity ~0.4 h after sunset when the temperature and light intensity were ~22°C and 30 lux, respectively.
Figure 3
Curves passing through mean values (N = 22) of the natural light intensity obtained at the breeding site of the haH strain (A) at Hemkund-Sahib (4,121 m) and the laH strain of D. helvetica (B) at Birahi (1,132 m). Data were collected from 1 to 21 July 2005 when the natural photoperiod was ~14 h and the ambient temperature was maintained at 20 ± 0.5°C, (i.e., the CT regime). The haH flies began activity ~4.5 h after sunrise (SR) when the light intensity was ~79,000 lux while the laH flies began activity ~1 h before sunrise when the light intensity was ~1 lux as in the NFT regime. The haH flies terminated activity ~1 h after sunset (SS) when light intensity was ~1 lux unlike that in the NFT regime, while the laH flies terminated activity ~0.4 h after sunset when the light intensity was ~30 lux as that in the NFT regime. Other symbols as in Figure 1.
Figure 4
Double plotted activity records of the representative male (# 25) of the haH strain (A) and the male (# 16) of the laH strain (B) of D. helvetica entrained by LD 12:12 cycles at 20 ± 0.5°C for 11 days under controlled laboratory conditions. The male of the haH strain had unimodal activity pattern with onset of activity occurring in the subjective forenoon, ~4.5 h after lights-on. The male of the laH strain, however, showed anticipation of the light-on transition and thereby began activity ~1 h before lights-on. Activity in both males ended after lights-off. The oblique arrow in each actogram on day 11 indicates the initiation of DD. There were three transient cycles before steady-state free running rhythms with τ > 24 h and τ < 24 were established in the haH male (A) and the laH male (B), respectively. The unimodal activity pattern of the haH male was retained in DD, but the bimodal activity pattern of the laH male was abolished in DD as the evening peak disappeared immediately after the transfer from LD 12:12 to DD.
Figure 5
Mean entrainment activity profile shown in histogram format for 21 males of each strain for 11 days in LD 12:12 cycles at 20 ± 0.5°C under controlled laboratory conditions. Males of the haH strain had a unimodal activity pattern in which activity onset occurred in the subjective forenoon, ~4.5 h after lights-on (A). Males of the laH strain had a bimodal activity pattern in which activity onset occurred ~1 h before lights-on (B). The other notations are the same as used in Figure 1.
Table 2
Entrainment and free-running parameters of D. helvetica strains in the laboratory
| Strain | Ψo | Ψe | α/ρ in LD 12:12 | TAPC in LD 12:12 | α/ρ in DD | τ (h) | TAPC in DD |
| haH | 4.5 (0.4) | - 1.1 (0.3) | 0.7 (0.3) | 596 (32) | 0.4 (0.2) | 26.1 (0.6) | 592 (59) |
| laH | -1.3 (0.4) | 0.4 (0.2) | 1.7 (0.4) | 782 (61) | 0.4 (0.1) | 21.7 (0.4) | 377 (32) |
Mean values (± SD, N = 21) for the phase of activity onset (Ψo), phase of activity end (Ψe), the ratio of activity phase to rest phase (α/ρ) and the total activity per cycle (TAPC) for males of the haH strain and the laH strain of D. helvetica entrained by LD 12:12 cycles at constant temperature of 20 ± 0.5°C in the laboratory.