SRA

Obligatory hematophagous arthropods such as lice, bugs, flies and ticks harbor bacterial endosymbionts which are expected to complete missing dietary needs, and numerous genomics and some experimental evidences currently support this expectation. In hard ticks (Acari: Ixodidae) serval linages of bacterial symbionts has been documented, and very few were experimentally shown to be essential to some aspects of tick's fitness, mostly showing reduction in reproductive fitness. In order to pinpoint the nature of hard ticks-nutritional symbionts interactions, we tested the effect of antibiotic treatment and massive elimination of Coxiella-like endosymbionts (CLE) on the development and fitness of the brown dog tick (Rhipicephalus sanguineus). Administration of ofloxacin to repleted nymphs resulted in significant and acute reduction of the tick microbial community load and in CLE numbers in subsequent life stages (aposymbiotic ticks). As a result, aposymbiotic female, but not male nymphs, suffered a delayed post-feeding development. Additionally, aposymbiotic adult females needed a significantly prolonged feeding period in order to replete, and had reduced engorgement weight. Weight conversion into eggs was lower in aposymbiotic females, which resulted in reduced fecundity, as well as excessive reduced fertility. Eggs produced by aposymbiotic females were also free of CLE and resulting aposymbiotic larvae were unable to feed successfully. These results first demonstrate that the observed effects are due to CLE reduction and not due to antibiotic administration; and second, suggest that the contribution of CLE to its Rh. sanguineus host is not mandatory for oocyte development and embryogenesis, but is required under high physiological demands such as blood meal processing and tissue build up, which are more prominent in females, presumably via supplementing the host with essential micro and macronutrients. Further nutrient complementary studies are required to support this hypothesis.