Photoresponsivity and motility in the planarian Schmidtea mediterranea vary diurnally

ABSTRACT

The planarian flatworm has become one of the leading animal model systems for studying stem cell behavior and tissue regeneration. Recent studies have shown that components of the circadian clockwork have important roles in tissue homeostasis and repair. However, it remains unknown whether planarians exhibit circadian or diurnal rhythms in physiology or behavior. Here, we developed a behavioral assay to evaluate diurnal activity in planarians based upon their well-established propensity to swim away from light (negative phototaxis). We show evidence that the planarian Schmidtea mediterranea has diurnal variability in negative phototaxis as a function of daily variation in motility. We also demonstrate that variation in planarian motility over 48 h occurs with 24-h periodicity. Our data suggest that S. mediterranea may be a useful model for studying the interplay between the circadian system and tissue regeneration.

KEYWORDS:

• Diurnal
• planarian
• motility
• photophobia
• circadian

Acknowledgements

This work was supported by Pennsylvania State System of Higher Education Faculty Professional Development Council 2015-16 grant to RJM, CLR, and RDH.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

This work was supported by the Pennsylvania State System of Higher Education [Faculty Professional Development Council 2015-16].