Impact of short-term temperature challenges on the larvicidal activities of the entomopathogenic watermold Leptolegnia chapmanii against Aedes aegypti , and development on infected dead larvae

GARCÍA, JUAN J.; RUEDA-PÁRAMO, MANUEL E.; LUZ, CHRISTIAN; LÓPEZ LASTRA, CLAUDIA C.; CATÃO, ALAINE M.L.; FERNANDES, ÉVERTON K.K.; RODRIGUES, JUSCELINO; MUNIZ, ELEN R.

Fungal Biology

elservier

Año: 2017

1878-6146

The oomyceteLeptolegnia chapmaniiis among the most promising entomopathogens for biologicalcontrol ofAedes aegypti. This mosquito vector breeds in small water collections, where this aquaticwatermold pathogen can face short-term scenarios of challenging high or low temperatures duringchanging ambient conditions, but it is yet not well understood how extreme temperatures might affectthe virulence and recycling capacities of this pathogen. We tested the effect of short-term exposure ofencystedL. chapmaniizoospores (cysts) onA. aegyptilarvae killed after infection by this pathogen tostressful low or high temperatures on virulence and production of cysts and oogonia, respectively. Cystswere exposed to temperature regimes between12C and 40C for 4, 6 or 8 h, and then their infectivitywas tested against third instar larvae (L3) at 25C; in addition, production of cysts and oogonia on L3killed by infection exposed to the same temperature regimes as well as their larvicidal activity weremonitored. Virulence of cysts to larvae and the degree of zoosporogenesis on dead larvae under labo-ratory conditions were highest at 25C but were hampered or even blocked after 4 up to 8 h exposure ofcysts or dead larvae at both the highest (35C and 40C) and the lowest (12C) temperatures followedby subsequent incubation at 25C. The virulence of cysts was less affected by accelerated than by slowthawing from the frozen state. The production of oogonia on dead larvae was stimulated by short-termexposure to freezing temperatures (12C and 0C) or cool temperatures (5C and 10C) but was notdetected at higher temperatures (25Ce40C). Thesefindings emphasize the susceptibility ofL. chapmaniito short-term temperature stresses and underscore its interest as an agent for biocontrol ofmosquitoes in the tropics and subtropics, especiallyA. aegypti, that breed preferentially in small volumesof water that are generally protected from direct sunlight