title: Neural coding underlying the cue preference for celestial orientation.
abstract: Diurnal and nocturnal African dung beetles use celestial cues, such as the sun, the moon, and the polarization pattern, to roll dung balls along straight paths across the savanna. Although nocturnal beetles move in the same manner through the same environment as their diurnal relatives, they do so when light conditions are at least 1 million-fold dimmer. Here, we show, for the first time to our knowledge, that the celestial cue preference differs between nocturnal and diurnal beetles in a manner that reflects their contrasting visual ecologies. We also demonstrate how these cue preferences are reflected in the activity of compass neurons in the brain. At night, polarized skylight is the dominant orientation cue for nocturnal beetles. However, if we coerce them to roll during the day, they instead use a celestial body (the sun) as their primary orientation cue. Diurnal beetles, however, persist in using a celestial body for their compass, day or night. Compass neurons in the central complex of diurnal beetles are tuned only to the sun, whereas the same neurons in the nocturnal species switch exclusively to polarized light at lunar light intensities. Thus, these neurons encode the preferences for particular celestial cues and alter their weighting according to ambient light conditions. This flexible encoding of celestial cue preferences relative to the prevailing visual scenery provides a simple, yet effective, mechanism for enabling visual orientation at any light intensity.
authors: Department of Biology, Lund University, 223 62 Lund, Sweden; basil.el_jundi@biol.lu.se.
authors: Basil
authors: B
authors: el Jundi
authors: Department of Biology, Lund University, 223 62 Lund, Sweden;
authors: Eric J
authors: EJ
authors: Warrant
authors: School of Animal, Plant, and Environmental Sciences, University of the Witwatersrand, Wits 2050, South Africa.
authors: Marcus J
authors: http://orcid.org/0000-0002-5155-2599
authors: MJ
authors: Byrne
authors: Department of Biology, Lund University, 223 62 Lund, Sweden;
authors: Lana
authors: L
authors: Khaldy
authors: Department of Biology, Lund University, 223 62 Lund, Sweden;
authors: Emily
authors: E
authors: Baird
authors: Department of Biology, Lund University, 223 62 Lund, Sweden;
authors: Jochen
authors: J
authors: Smolka
authors: Department of Biology, Lund University, 223 62 Lund, Sweden; School of Animal, Plant, and Environmental Sciences, University of the Witwatersrand, Wits 2050, South Africa.
authors: Marie
authors: M
authors: Dacke
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology; D001517:Coleoptera / Q000502:physiology* / Q000528:radiation effects; D003463:Cues; D017753:Ecosystem; D004777:Environment; D008027:Light; D016081:Moon; D009043:Motor Activity / Q000528:radiation effects; D009474:Neurons / Q000502:physiology*; D009949:Orientation / Q000502:physiology* / Q000528:radiation effects; D016082:Solar System; D013472:Sunlight
keywords: central complex; dim light; insect; navigation; vision