Could canid-human interactions produce suitable substrates for Lutzomyia longipalpis oviposition and immature development?

Abstract

Prehistoric fox-human interactions in South American caves could have shaped nutrient-rich habitats, favourable to sand fly immatures development. However, surviving on iron-rich and decomposing prey carcases or carnivore feces might be challenging and favour few species. Lutzomyia longipalpis is a cave sandfly adapted to cities, suggesting a pre-adaptation to human-polluted habitats. We tested substrates expected to be found in fox dens or ancient human trash mounds, as female oviposition and immature feeding choices. Further, we described general patterns of oviposition behaviour, to test positive feedback of a favourable microhabitat with previous laid eggs. Females were exposed to six substrate smells: fresh dog feces; rotten dog feces; fresh hairless mice; rotten hairless mice; forest litter; distilled water. Then, to test density-dependence in oviposition, gravid females were left in recipients for five days and changed to clean ones, under different quantities. We also simulated oviposition choices under distinct egg densities, using dodecanoic acid. Immatures were exposed to these substrates to test choice and ability to fully develop on them. The substrates more chosen for oviposition were canid flesh feces, decomposed mouse, water, and flesh mouse respectively. Number of laid eggs per female decreased with female density. On average of 43% eggs were retained and laid later when surviving females were transferred to clean recipients. Early emerged immatures showed no preference for substrates while late instars joined gradually onto decomposed corpses until pupating. The patterns of oviposition choice and immature survival are compatible with the hypothesis of a long-term adaptation of this species.