Towards a Characterization of the Locomotor Activity Rhythm of the Supralittoral Isopod Tylos europaeus

Abstract

Freshly collected samples of Tylos europaeus from Korba beach (northeast of Tunisia) were housed in an environmental cabinet at controlled temperature (18°C ± .5°C) and photoperiod. Locomotor activity was recorded under two photoperiodic regimens by infrared actography every 20 min by multichannel data loggers. One regimen simulated the natural light-dark cycle on the day of collection, whereas the second imposed a state of continuous darkness on all individuals. Under entraining conditions, the animals displayed rhythmic activity, in phase with the period of darkness, whereas in continuous darkness these isopods exhibited a strong endogenous rhythm with circadian and semidiurnal components at mean periods of τ (h:min) = 25:09 ± 01:02 h and τ = 12:32 ± 00:26 h, respectively. Under free-running conditions, this endogenous rhythm showed significant intraspecific variability. (Author correspondence: [email protected])

Keywords:

• Circadian
• Free-running
• Isopod crustacean
• Semidiurnal rhythm
• Tylos europaeus

ACKNOWLEDGMENTS

This study was supported by WADI project (INCO-CT2005-015226).

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.