The interaction between cuticle free fatty acids (FFAs) of the cockroaches Blattella germanica and Blatta orientalis  and hydrolases produced by the entomopathogenic fungus Conidiobolus coronatus

Abstract

The interactions between entomopathogenic fungi and insects serve a classic example of a co-evolutionary arms race between pathogens and their target host. The cuticle, site of the first contact between insects and entomopathogenic fungus, is an important defensive barrier against pathogens. It is covered by a layer of lipids that appears to play a key role in these processes and cuticular free fatty acid (FFA) profiles are consider as a determinant of susceptibility, or resistance, to fungal infections. These profiles are species-specific. The cockroaches Blattella germanica (Blattodea: Blattidae) and Blatta orientalis (Blattodea: Ectobiidae) are unsusceptible to the soil fungus Conidiobolus coronatus (Entomophthorales: Ancylistaceae) infection, therefore we studied the profiles of FFAs in order to understand the defensive capabilities of the cockroaches. The fungus was cultivated for three weeks in minimal medium. Cell-free filtrate was obtained, assayed for elastase, N-acetylglucosaminidase, chitobiosidase and lipase activity, and then used for in vitro hydrolysis of the cuticle from wings and thoraces of adults and oothecae. The amounts of amino acids, N-glucosamine and FFAs released from the hydrolysed cuticle samples were measured after eight hours of incubation. The FFA profiles of the cuticle of adults, and the wings, thoraces and oothecae of both species were established using GC-MS and the results were correlated with the effectiveness of fungal proteases, chitinases and lipases in the hydrolyzation of cuticle samples. Positive correlations would suggest the existence of compounds used by the fungus as nutrients, whereas negative correlations may indicate that these compounds could be engaged in insect defence.

The type of blood used to feed Aedes aegypti females affects their cuticular and internal free fatty acid (FFA) profiles

“…In addition, the chemical composition of cuticular FFAs may influence the susceptibility of cockroaches ( Blatella germanica and Blatta orientalis ) to infection by the fungus M . anisopliae [ 87 ] or Conidiobolus coronatus [ 88 ]. Similarly, cuticular FFAs of corn earworm larvae ( Heliothis zea ), inhibit the germination and growth of entomopathogenic fungus Beauveria bassiana [ 89 ].…”

“…The TMS values of the fatty acids were then analysed by GC-MS. The method is based on literature data [ 88 , 95 , 129 , 149 ].…”

Metamorphosis-related changes in the free fatty acid profiles of Sarcophaga (Liopygia) argyrostoma (Robineau-Desvoidy, 1830)

“…The FFAs in the insect cuticle have also been identified as resistance factors against fungal infection; for example, Gołębiowski and co-workers report that cuticular FFAs play a role in resistance to fungal infection by the flies Calliphora vicina , Lucilia sericata , C. vomitoria and S. carnaria 26 , 39 – 41 , 76 , 77 . Also, literature data postulate that the chemical composition of cuticular FFAs may influence the susceptibility of cockroaches ( Blatella germanica, Blatta orientalis) to infection by the fungus Metarhizium anisopliae 78 and by Conidiobolus coronatus 79 . Additionally, Smith and Grula indicate that cuticular FFAs in corn earworm larvae ( Heliothis zea ) can inhibit the germination and growth of Beauveria bassiana 80 .…”

“…Cuticular and internal lipid components of insects were extracted, separated and analysed by GC–MS. The method of extraction was based on literature data (for example 43 , 44 , 76 , 79 , 144 ). Lipids from larvae, pupae and adults were extracted first in 20 ml of petroleum ether (Merck Millipore, Germany) for 5 min (extract I) and then again in 20 ml of dichloromethane (Merck Millipore, Germany) for 5 min (extract II) to yield cuticular lipids.…”

“…Response factors of one were assumed for all constituents. The method is based on literature data 43 , 44 , 76 , 79 , 144 .…”