Neurogenetic studies of the egg-laying rhythm of drosophila melanogaster

Abstract

Nearly all organisms on Earth are subject, in one way or the other, to the effects of the planet’s daily rotation about its axis and need to adjust their physiology and behaviour to the daily cycling of environmental conditions. The observation that living things exhibit rhythms in their physiology is not a recent one: as far back as the early 18th century, Jacques d’Ortous de Mairan noted that the common “touch-me-not” plant of the Fabaceae family opened and closed its leaves once every 24 hours, even when placed in the dark without any light stimulus (de Mairan, 1729), indicating that something within the plant was producing the rhythmic phenomenon, rather than it being merely a reaction to rhythmic stimuli. The clinching evidence for an endogenous source of daily rhythms came nearly two centuries later however, when Erwin Bünning demonstrated that navy bean plant variants differed in their endogenous periodicities from 24 h (Bünning, 1935). He correctly deduced that this meant the plants were not following a rhythmic environmental cue that repeated itself everyday, as this would produce exactly 24 h rhythms – instead, something from within the plant was producing a rhythm with a near-24 h period.