Metabolic correlates in the working of an insect putative photoperiodic clock

Abstract

Analysis of the formal properties of photoperiodic systems has emphasized the importance of two discrete phases of nocturnal light sensitivity (the so-called points A and B) in a variety of taxa. This has been exemplified in the lepidopteran, Pieris brassicae, among other species, since the illumination of either of these phases in an otherwise short-day cycle (diapause inducing) gives rise to a long-day effect (development without diapause). In this species, the photoreceptor of diel cycles and the clock-counter system are very likely brain located. Using cytochrome oxidase activity as a marker of energy metabolism, a neuroanatomical base in the brain involved in long-day responses elicited by light at points A and B was investigated.