Short-term changes in activity rhythms in an intertidal arthropod (Acarina: Bdella interrupta Evans)

Area of Science:

• Marine Biology
• Animal Behavior
• Chronobiology

Background:

• Intertidal zones present unique environmental challenges, including regular tidal cycles.
• Organisms in these zones often exhibit adaptations to cope with submergence and emergence.
• The mite Bdella interrupta inhabits marine saltmarshes, experiencing predictable tidal fluctuations.

Purpose of the Study:

• To investigate the locomotory activity patterns of the intertidal mite Bdella interrupta.
• To determine if tidal cycles influence the mite's activity rhythms.
• To understand the adaptive significance of these rhythms for survival.

Main Methods:

• Observing and recording the locomotory activity of Bdella interrupta on a marine saltmarsh.
• Analyzing activity patterns during periods of tidal submergence and emergence.
• Comparing observed activity periodicities with known tidal and circadian cycles.

Main Results:

• Bdella interrupta displays distinct daily peaks in surface locomotory activity.
• During tidal submergence, activity peaks showed a periodicity of approximately 12.5 hours, indicative of a tidal rhythm.
• In the absence of submerging tides, the activity periodicity shifted to approximately 11.5 hours.

Conclusions:

• The mite possesses a circatidal clock that entrains to tidal cycles.
• The observed shift in periodicity suggests a free-running or phase-shifting mechanism in response to altered tidal cues.
• The rhythm adjustment likely ensures activity during daylight and minimizes inundation risk during critical spring tides.