Proboscis infection route of Beauveria bassiana triggers early death of Anopheles mosquito

Abstract

Entomopathogenic fungi are known to control vector mosquito populations. Thus, understanding the infection dynamics of entomopathogenic fungi is crucial for the effective control of insect pests such as mosquitoes. We investigated the dynamics of Beauveria bassiana s.l. 60-2 infection of Anopheles stephensi by exposing the mosquito to fungus-impregnated filter paper through two infection routes and then comparing the mortality and extent of infection. Fungal development was observed after using this inoculation method with both the tarsus route and the proboscis route, but early mosquito death occurred only after infection through the proboscis route. Fungal hyphae invaded almost all the tissues and organs before or after the death of the host, and fungal invasion of the brain was highly correlated with mortality. Moreover, although all mosquitoes that were alive at various time points after inoculation showed no fungal infection in the brain, fungal infection was detected in the brain in all dead mosquitoes. Our results suggest that fungal invasion of the brain represents one of the factors affecting mortality, and that the proboscis route of infection is critical for the early death of vector mosquitoes.

Gene diversity explains variation in biological features of insect killing fungus, Beauveria bassiana

“…Beauveria bassiana is one of the most studied species and its isolates have been commercialized worldwide as mycoinsecticides 7 , 8 . This species is composed of diverse isolates able to exploit a wide range of environments and has a broad range of arthropod hosts 9 – 11 . Although many B. bassiana -based mycoinsecticides have been produced worldwide, they are still underused because of industrialization conflicts concerning how the isolates are different.…”

Fungi and Oomycetes–Allies in Eliminating Environmental Pathogens

“…They observed that the larvae exposed to the action of nymphs (predatory role) were much more vulnerable, in the adult stage, to the action of B. bassiana spores [89]. Ishii et al [90] demonstrated the adulticidal action of B. bassiana conidia against An. stephensi mosquitoes.…”

“…stephensi mosquitoes. Seven days after exposure, the insect's body was completely invaded by hyphae [90]. Oomycetes Lagenidium giganteum, Aphanomyces laevis, Couchia spp., Crypticola spp., Leptolegnia caudata and Pythium spp.…”

The potential of the Beauveria bassiana MHK isolate for mosquito larval control

“…Sorokin (Hypocreales: Clavipitaceae), an opportunistic fungal entomopathogen that has shown promise for the control of larvae and adults of the African malaria mosquito, Anopheles gambiae Giles (Diptera: Culicidae) in laboratory and semi-field environments (Bukhari et al 2011, Fawrou et al 2013, Lovett et al 2019). Similarly, the ascomycetous fungus, Beauveria bassiana (Balsamo) Vuillemin (Hypocreales:Cordycipitaceae), is an entomopathogenic fungus that has a wide host range, including larvae and adults of several mosquito species (Clark et al 1967, 1968, Miranpuri and Khachatourians 1991, Geetha and Balaraman 1999, Bukhari et al 2010, 2011, Darbro et al 2012, Ishii et al 2017, Benzina et al 2018). B. bassiana infects mosquito larvae by attaching to the larval body at the head and perispiracular lobes of the siphon (Clark et al 1968, Miranpuri and Khachatourians 1991) and through ingestion of fungal spores (Miranpuri and Khachatourians 1990).…”