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.