Cuticular Lipids as a First Barrier Defending Ixodid Ticks against Fungal Infection.

The chemical composition of tick cuticles acts as a barrier to pathogens and may limit infection by entomopathogenic fungi. This study characterized the cuticular neutral lipids (NL) and hydrocarbons (HCs) of four ixodid ticks that are widely distributed in Brazil. HC extracts were analyzed by gas chromatography-mass spectrometry and used to challenge IP361 and IP146; the effect of cuticular extracts in fungal growth were evaluated by disk diffusion and conidial viability assays. In addition, conidial germination on the tick cuticle was evaluated by scanning electron microscopy, and NL from ticks treated with fungi were assessed by thin layer chromatography. Six HCs were exclusively identified in . Additionally, cuticle extracts from and inhibited the growth of IP146 and reduced conidial germination of IP361 to 70% and 49%, respectively; the same extracts also produced cytotoxic effects, with conidial death above 30% and 60%. Electron micrographs showed a delayed germination of conidia incubated for 48 h or 72 h on and . The lipid profile of treated with fungi was not significantly altered; triacylglycerol was not detected in the cuticle extracts of any other tick species. Finally, and cuticles have lipid components that may limit the development of