title: Long-term imaging of circadian locomotor rhythms of a freely crawling C. elegans population.
abstract: BACKGROUND
  Locomotor activity is used extensively as a behavioral output to study the underpinnings of circadian rhythms. Recent studies have required a populational approach for the study of circadian rhythmicity in Caenorhabditis elegans locomotion.
  
  
  METHODS
  We describe an imaging system for long-term automated recording and analysis of locomotion data of multiple free-crawling C. elegans animals on the surface of an agar plate. We devised image analysis tools for measuring specific features related to movement and shape to identify circadian patterns.
  
  
  RESULTS
  We demonstrate the utility of our system by quantifying circadian locomotor rhythms in wild-type and mutant animals induced by temperature cycles. We show that 13 °C:18 °C (12:12h) cycles are sufficient to entrain locomotor activity of wild-type animals, which persist but are rapidly damped during 13 °C free-running conditions. Animals with mutations in tax-2, a cyclic nucleotide-gated (CNG) ion channel, significantly reduce locomotor activity during entrainment and free-running.
  
  
  CONCLUSIONS
  Current methods for measuring circadian locomotor activity is generally restricted to recording individual swimming animals of C. elegans, which is a distinct form of locomotion from crawling behavior generally observed in the laboratory. Our system works well with up to 20 crawling adult animals, and allows for a detailed analysis of locomotor activity over long periods of time.
  
  
  CONCLUSIONS
  Our population-based approach provides a powerful tool for quantification of circadian rhythmicity of C. elegans locomotion, and could allow for a screening system of candidate circadian genes in this model organism.
authors.affiliation: Department of Biology, University of Nevada, Reno, NV 89557, USA. Electronic address: awinbush237@gmail.com.
authors.forename: Ari
authors.initials: A
authors.lastname: Winbush
authors.affiliation: Department of Biology, University of Nevada, Reno, NV 89557, USA. Electronic address: matthew.gruner@gmail.com.
authors.forename: Matthew
authors.initials: M
authors.lastname: Gruner
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada, School of Medicine, Reno, NV 89557, USA. Electronic address: grant@medicine.nevada.edu.
authors.forename: Grant W
authors.initials: GW
authors.lastname: Hennig
authors.affiliation: Department of Biology, University of Nevada, Reno, NV 89557, USA. Electronic address: avanderlinden@unr.edu.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: van der Linden
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D017173:Caenorhabditis elegans / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008124:Locomotion / Q000502:physiology*; D014741:Video Recording
keywords: C. elegans; Circadian rhythms; Crawling; Locomotion; Population; Temperature