Churchill Alice C.L., Rot Asael

The fungus Metarhizium anisopliae (Hypocreales: Clavicipitaceae) is an efficient biological control agent of various arthropods, actively penetrating host cuticles via penetration pegs, colonizing the host body, and causing host death. Laboratory assays against various hosts (ticks and insect) have revealed that while some hosts are highly susceptible to the fungus, other hosts are resistant to infection. Results of previous studies of the factors involved in host susceptibility have suggested that cuticular compounds from susceptible and resistant hosts may differentially influence fungus development. This work describes the microscopic development of a GFPexpressing M. anisopliae strain on ticks (Acari: Ixodidae); susceptible host Rhipicephalus annulatus, and the resistant host Hyalomma excavatum. Conidia were observed germinating on all hosts examined. However, the fungus was observed penetrating host cuticles only on susceptible hosts and never on resistant hosts. Moreover, growth of germinating conidia and the hyphae that developed from them was inhibited on resistant hosts and died within a few days. Analyzing these observations provides new information on the specificity and importance of each event of the host-pathogen interaction for a successful mycosis.