Ignell, R. | bioRxiv Science

bioRxiv2020

Malaria mosquitoes acquire and allocate cattle urine to enhance life history traits

Nutrient acquisition and allocation integrate foraging and life-history traits in insects. To compensate for the lack of a particular nutrient at different life stages, insects may acquire these through supplementary feeding on e.g., vertebrate secretions, in a process known as puddling. The mosquito Anopheles arabiensis emerges undernourished, and as such, requires nutrients for both metabolism and reproduction. Host-seeking and blood-fed An. arabiensis are attracted to the natural and synthetic odour of cattle urine, which signals a source of nutrients, but not the presence of a host or oviposition site. Females actively imbibe cattle urine, and its main nitrogenous compound, urea, and allocate these resources according to life history trade-offs to flight, survival or reproduction, as a function of physiological state. As a consequence, this behaviour affects vectorial capacity by increasing daily survival and vector density, and thus should be considered in future models. Future vector management strategies are discussed.

ecology↗

bioRxiv2020

Comparative morphological and transcriptomic analyses reveal novel chemosensory genes in the poultry red mite, Dermanyssus gallinae and knockdown by RNA interference

Detection of chemical cues via chemosensory receptor proteins are essential for most animals, and underlies critical behaviors, including location and discrimination of food resources, identification of sexual partners and avoidance of predators. The current knowledge of how chemical cues are detected is based primarily on data acquired from studies on insects, while our understanding of the molecular basis for chemoreception in acari, mites in particular, remains limited. The poultry red mite (PRM), Dermanyssus gallinae, is one of the most important blood-feeding ectoparasites of poultry. Unlike other ectoparasites on animals, PRM feeds mainly at night. During daytime, these animals hide themselves in crevices around the poultry house. The diversity in habitat usage, as well as the demonstrated host finding and avoidance behaviors suggest that PRM relies on their sense of smell to orchestrate complex behavioral decisions. Comparative transcriptome analyses revealed the presence of candidate variant ionotropic receptors (IRs), odorant binding proteins (OBPs), niemann-pick proteins type C2 (NPC2) and sensory neuron membrane proteins (SNMPs). Some of these proteins were highly and differentially expressed in the forelegs of PRM. Rhodopsin-like G protein-coupled receptors (GPCRs) were also identified, while insect-specific odorant receptors (ORs) and odorant co-receptors (ORcos) were not detected. Furthermore, using scanning electron microscopy (SEM), the tarsomeres of all legs pairs were shown to be equipped with sensilla chaetica with or without tip pores, while wall-pored olfactory sensilla chaetica were restricted to the distal-most tarsomeres of the forelegs. Further, using the conserved odorant binding protein (OBP) as a test case, the results showed that RNA interference (RNAi) can be induced in D. gallinae chemosensory tissues. This study is the first to describe the presence of chemosensory genes in any Dermanyssidae family. It is also the first report of chemosensory gene knockdown by RNAi in any mite species and demonstrate that their diminutive size, less than 1 mm, is not a major impediment when applying gene knockdown approaches. Our findings make a significant step forward in understanding the chemosensory abilities of D. gallinae.

molecular biology↗