Master 2 Internship in behavioural ecology and physiology (January-June 2023) --------- Does the nutritional status of Eupelmus vuilleti females influence their JH levels and aggressiveness during femalefemale competition for host access? Key words: nutrition, hormones, agonistic behavior, parasitoid wasps Rationale and objectives: Animal behaviours are classically mediated by hormone circulating levels, which, in turn, are driven by the individual’s nutritional status. In many insects, nutritional status influences Juvenile Hormone (JH) synthesis and thus, the level of circulating JH: eating increases the level of insulin which leads to JH production by the corpora allata. In contrast, when they are starving, JH production is no longer stimulated and circulating JH levels decrease. Nutritional status can also modulated the costs and benefits of behavioural strategies. In this context, we aim to explore the effect of nutrition (especially host-feeding) on JH production and female aggressiveness during dyadic contest for an indivisible resource (the host) in a parasitoid wasp Eupelmus vuilleti. We expect feeding (in particular sugars) to increase JH levels, which in turn will increase female aggressiveness during contest (Mathiron et al. 2019). Sugars may also increase females’ ability to fight and their capacity to sustain agonistic interactions, hence their probability of winning contest. In contrast, starved females may place a higher value in the contested resource (the host on which they can feed), what may increase their motivation, hence their probability of getting access to the resource. In this later case, we would not expect females to sustain long agonistic interactions. The main aim of this project is therefore to investigate the relative effect of host-feeding on agonistic behaviours and JH levels, and deepen our understanding of the relationships between hormones, nutritional status and agonistic behaviours. Presentation of the biological model: Eupelmus vuilleti Crawford (Hymenoptera: Eupelmidae) is an ectoparasitoid. Females parasitize and feed on larvae and pupae of the cowpea weevil, Callosobruchus maculatus (Fab) (Coleoptera: Bruchidae), which infest cowpea seeds, Vigna unguiculata (L.) Walp (Fabaceae). They can feed from and lay eggs on the same hosts. Callosobruchus maculatus hemolymph contains various nutrients: proteins, lipids, sugars (e.g. sucrose, trehalose), glycogen (Giron et al. 2002). Host-feeding increases both egg production and longevity. Injections of sucrose and trehalose at C. maculatus hemolymph concentrations directly into the parasitoid hemolymph lead to an increase in female longevity (Giron et al. 2002). They are simple sugars that can be assimilated when directly injected into the parasitoid hemolymph. The increase in fecundity is mainly determined by the amount of lipids obtained (Giron et al. 2004). It was estimated that one host-feeding event increases the lifetime by 0.3 days and allows the production of 1.5 eggs (Giron et al. 2004). Moreover, it has been shown that JH-supplemented E. vuilleti females (via an injection) are more aggressive when fighting for hosts against intraspecific competitors than control females supplemented with vehicle (Mathiron et al. 2019). Methods: Behavioural observations, micro-injections, dissections, chemical extractions. Location: IRBI UMR 7261 CNRS – Université de Tours, Faculté des Sciences et Techniques, Tours To apply, please contact Marlène Goubault (marlene.goubault@univ-tours.fr ) & Charlotte Lécureuil (charlotte.lecureuil@univ-tours.fr) before the 24th of October. We will be happy to read your CV and motivation letter. Please provide the name of two references, and if possible one appreciation letter. References: Mathiron AGE, Earley RL & Goubault M. 2019. Juvenile hormone manipulation affects female reproductive status and aggressiveness in a non-social parasitoid wasp. General and Comparative Endocrinology 274: 80-86 Giron D, Rivero A, Mandon N & Casas J. 2002. The physiology of host feeding in parasitic wasps: implications for survival. Functional Ecology 16: 750–757 Giron D, Pincebourde S & Casas J. 2004. Lifetime gains of host-feeding in a synovigenic parasitic wasp. Physiological Entomology 29: 436–442