Relationships between biological characteristics of the crustacean amphipod Talitrus saltator, including behavioural responses, and local environmental features. Case studies of Zouara and Korba (Tunisia)

Abstract. A geomorphological and biological multidisciplinary approach was performed to analyse the relationships between the biological characteristics of the crustacean amphipod Talitrus saltator, including behavioural responses, and local environmental features. To this aim, two Tunisian sandy beaches, Zouara and Korba, located respectively on the western and eastern Mediterranean coasts, were investigated. These two localities present different physical, morphological, and landscape characteristics. Zouara beach is a well-developed beach backed by considerable coastal dunes and is one of the most extended beaches in Tunisia. It is very exposed to the north-western winds, being part of a coastal sector well known for storm frequency and violence mainly during the winter season. Korba beach is located on the eastern coast of the Cap Bon Peninsula and is protected from northern and north-western winds. It is also characterized by the presence of sebkhas and chotts in the retrodunal area, which constitute one of the most striking aspects of the morphology of this coast. Orientation behaviour, activity rhythms and genetic diversity were investigated in Talitrus saltator populations from the two beaches to assess the potential relations of the different beach characteristics on this species. Orientation experiments under dry conditions showed that the Korba population had a mean escape direction not substantially deviating from the theoretical escape direction seawards, whereas the Zouara population exhibited a higher dispersion with a significant deviation from the local seawards direction. Regarding the locomotor activity under constant laboratory conditions, the data indicated a significant difference in the circadian period and rhythmicity rate between the two populations. The most clearly defined circadian rhythms were found in the Korba population. The genetic diversity, analysed through allozymic analysis, showed a greater variation in the Korba population than in the Zouara one. The analysis of the polymorphism of the mtDNA COI gene indicated a similar tendency. The different approaches converged on a relation between the characteristics of the beach and the biological responses of T. saltator, showing the highest biological stability on the less exposed beach of Korba.