Some parasites use olfactory cues to detect their hosts and, since bacterial symbionts are partially responsible of animal odors, they could also determine parasitism of their hosts. By experimental manipulation of the microbiota of hoopoe (Upupa epops) nests before reproduction started, we explore the hypothetical links between symbiotic bacteria and volatiles, and between both of them and parasitism. We estimated level of ectoparasitism of chewing lice in females and of Carnus haemapterus flies in nestlings, characterized microbial communities (from nest materials and uropygial secretions), and volatile profiles (from nest environment and uropygial secretion) during the nestling stage. Nests with autoclaved nest material had less diverse bacterial communities, more diverse volatile-profiles, and their occupants experienced lower intensity of parasitism than those in control nests. The experiment also affected beta diversity of the microbial communities of nest material and volatiles of the nestling uropygial-secretions. Moreover, microbial communities of uropygial secretions and nest materials covaried with their volatile profiles, while the volatile profile of secretions explained nest odor. Finally, some of the volatiles and bacteria detected in the nest material and secretions were associated with ectoparasitism intensity of females and nestlings, and with fledging success. These results support the expected links between microbial communities and animal odors, and strongly suggest that the associations between symbiotic bacteria and both ectoparasitism and reproductive success are partially mediated by volatiles of bacterial origin. Future work should focus on mechanisms explaining the detected patterns.

Perfil de volátiles: Cromatografía de gases-espectrometría de masas (GC-MS)

Los análisis se realizaron en cromatografía de gases acoplada a un espectrómetro de masas Varian 450GC 240MS con un inyector automático Combi Pal a fibra SPME (50/30 μm DVB/CAR/PDMS, Stableflex 23Ga, Autosampler). La desorción del inyector fue a 250 ºC durante 10 minutos en Split (20:1) y el flujo de helio a 2mL/min. La columna capilar fue Aligent HP-FFAP 30m X 0.32mm X 0.25 μm. La temperatura del horno se inició a 50 ºC durante 1 min. Después de la inyección de la muestra (10 μL), el horno se programó para aumentar de 5 ºC/min a 100 ºC, luego a 10 ºC/min a 200 ºC y de 50 ºC/min a 250 ºC durante 1min. El rango de barrido del espectrómetro de masas estaba en modo TIC Full Scan entre 30 y 500 m/z. La identificación de compuestos se estableció mediante el análisis de SIM de iones característicos y la biblioteca de espectro NIST 08.