Endogenous activity rhythm in Talitrus saltator, Britorchestia brito (Crustacea, Amphipoda) and Tylos europaeus (Crustacea, Isopoda) from Barkoukech Beach (Tabarka, Tunisia)

Abstract

The locomotor activity rhythm of three supralittoral crustacean species, Tylos europaeus (terrestrial isopod) and Britorchestia brito and Talitrus saltator (amphipod, Talitridea), was investigated in Barkoukech Beach. The rhythm was monitored in individual animals in spring under continuous darkness and constant temperature. Results revealed that whatever the species, actograms and mean activity curves showed that specimens of T. europaeus and T. saltator concentrated their activity during the subjective night; whereas, B. brito concentrated its activity during the subjective day. The three species exhibited a circadian locomotor rhythm with mean circadian period, respectively, equal to 24h41′ ± 0h44′, 24h46′ ± 0h55′ and 25h21′ ± 1h16′. The most stable locomotor rhythm was found in T. saltator (0.444 ± 0.246). Furthermore, individuals of T. europaeus were significantly more active (10h47′ ± 2h52′) than the two amphipods. Differences in the activity patterns of the three species will be discussed as an adaptative strategy to respond to interspecific competitive interactions.

Keywords:

• Barkoukech Beach
• endogenous rhythm
• constant darkness
• Tylos europaeus
• Talitrus saltator
• Britorchestia brito

Acknowledgements

The study was supported by the Research Unit of Bio-ecology and Evolutionary Systematics (UR11ES11), Faculty of Science of Tunis, University of Tunis El Manar.

Disclosure statement

No potential conflict of interest was reported by the authors.