Defense in french
Team : Interindividual Variability and Emergent Plasticity (IVEP), CRCA-CBI
Supervisor : Raphaël Jeanson (CRCA-CBI)
Committee members :
- Marlène Goubault-Body, Rapporteure (IRBI, Université de Tours)
- Damien Charabidze, Rapporteur (CHJ, Université de Lille)
- Audrey Dussutour, Examinatrice (CRCA, Université Toulouse 3)
- Julien Bacqué-Cazenave, Examinateur (EthoS, Université de Caen)
- Julien Cote, Examinateur (EDB, Université Toulouse 3)
Abstract :
Sociality, which represents a crucial step in the evolution of the complexity of living systems, has evolved repeatedly in vertebrates and invertebrates. Sociality covers an incredible variety of forms, from transitory groupings of usually solitary individuals to species living in integrated societies, called eusocial species. Although the transition to eusociality is still of great interest, this type of social organisation is not representative of the diversity of social forms in invertebrates. It is therefore necessary to identify the common features of all forms of social life in order to understand the origins of permanent sociality. The study of species with a transient social life is of particular interest, since in these species, juveniles live together for varying lengths of time, then disperse to live on their own. From a distal perspective, the ontogenic variations in social behaviour is probably accompanied by a change in the costs and benefits of group living. From a proximal point of view, the mechanisms that trigger the transition from a temporary and non-facultative social lifestyle to a solitary life are not yet understood. Spiders are a relevant model for understanding social transitions, as all spider species (> 51,500) exhibit a transient social phase: juveniles are gregarious and tolerants, then become solitary and aggressive as adults (except for 20 spider species that remain social throughout their lives). Previous work has shown that the social isolation that results from the natural dispersion of spiders triggers their aggression. The main objectives of my thesis were therefore to examine the communication modalities involved in maintaining social tolerance in the solitary spider Agelena labyrinthica, and to characterise the impact of social isolation on the perception and integration of social signals. By manipulating the social context during ontogeny in juveniles, we demonstrated the existence of an ontogenetic development of aggressiveness, revealed the existence of metabolomic differences according to the social context, showed that the onset of cannibalism does not result from a reduction in energy reserves, demonstrated that social tolerance can be restored after moulting, and finally observed that the maintenance of tolerance requires the perception of a signal emitted by a living spider. Through various behavioural approaches, this thesis suggests that the communication change underlying the decline of social tolerance in spiderlings involved a change in the perception and/or interpretation of communication signals by isolated individuals.
University Paul Sabatier - Toulouse III
