Environmental modulation of small-scale exploration in weakly electric fish

Animals actively explore their surroundings to efficiently obtain resources, relying on the sensory modalities available to them. In South American weakly electric fish, self-generated electric organ discharges (EODs) create a short-range 'sensory bubble' that, together with locomotion, supports exploration. This behavior relies on the coordinated modulation of spatial movement and electromotor activity, reflected in changes in EOD rate (EODr). However, how these components are engaged in natural contexts, and which conditions are sufficient to elicit exploration, remain poorly understood. Here, we examined how environmental and contextual factors modulate exploratory behavior in Gymnotus omarorum by combining a minimalistic laboratory assay with multi-day recordings in a seminatural arena. In laboratory tanks, freely moving fish showed minimal locomotor activity, which increased only when darkness and a novel electrosensory stimulus co-occurred, indicating strong context dependence and gating by chronobiological and motivational factors. By contrast, under seminatural conditions preserving natural light and temperature cycles, fish exhibited robust nocturnal rhythms in both locomotor activity and EODr. Chronobiological analysis revealed that the electrosensory rhythm consistently preceded the locomotor rhythm, with individual phase differences correlated across behaviors. These results show that exploration is a temporally organized behavior arising from coordinated modulation of sensory and motor systems. By linking electrosensory activity, locomotion and circadian timing under ecologically relevant conditions, this study provides insight into how animals regulate sensory sampling and movement during exploration.