Figure 5 from: Espinasa L, Collins E, Finocchiaro A, Kopp J, Robinson J, Rutkowski J (2016) Incipient regressive evolution of the circadian rhythms of a cave amphipod. Subterranean Biology 20: 1-13. https://doi.org/10.3897/subtbiol.20.10010

Figure 5 - Entrainment by light is apparently not functioning in the Ice Cave (A–C and A'–C') and Clarksville Cave (D–G) populations. In Stygobromus allegheniensis, the second dark period lacks the anticipation and synchronization of a period of activity, which is a hallmark of organisms possessing a light-entrained circadian rhythm. Black boxes indicate periods while in darkness and white boxes indicate illuminated conditions.