Intra-annual variation of the locomotor behaviour of Talitrus saltator (Amphipoda, Talitridae) from Ghar El Melh

ABSTRACT

The seasonal variation of the locomotor activity rhythm of Talitrus saltator was investigated in a population from the supra-littoral zone of the new harbour beach of Ghar El Melh. The rhythm was recorded in individual animals over the four seasons under two simultaneous experimental regimens: the natural light/dark cycle and the continuous darkness. Results revealed that, whatever the season, actograms and mean activity curves showed globally that individuals of T. saltator concentrated their activity during the experimental and subjective day. In addition, specimens exhibited a nocturnal circadian rhythm of locomotor activity with an ultradian component. Under light–dark cycle, circadian periods determined by periodogram analysis in four seasons were appreciably similar and were close to 24 h. Under constant darkness, the circadian period was longer in the autumn (τ_DD = 1501ʹ.81 ± 56ʹ.2) than the other seasons. In addition, the study of the mean activity times calculated for four seasons showed that the most important activity of individuals was observed in the spring and the autumn under entraining and free-running conditions, respectively.

KEYWORDS:

• Ghar El Melh
• beach
• Talitrus saltator
• light–dark
• constant darkness

Disclosure statement

No potential conflict of interest was reported by the authors.