Symbiont dynamics during the blood meal of Ixodes ricinus nymphs differ according to their sex

Ticks harbour rich and diverse microbiota and, among the microorganisms associated with them, endosymbionts are subject of a growing interest due to their crucial role in biology arthropod host. Midichloria mitochondrii is main endosymbiont European tick Ixodes ricinus found abundance all I. females, while at much lower density males, where it even absent 56 % individuals. This also known increase numbers after blood meal larvae, nymphs or females. Because this difference prevalence M. between two sexes, surveying these bacteria that will become either females males could help understand behaviour its To aim, we have set up an experimental design by building 3 groups unfed based on scutum hypostome lengths. After engorgement, weighing moulting subset nymphs, significant sex-ratio was observed. In parallel, load individual quantified qPCR both before engorgement. No body mass observed stage, but following features were significantly different each size group. Our results demonstrate symbiont dynamics during nymphal engorgement resulting higher The consequences those findings our understanding interplay host discussed.