GROWTH OF THE ENTOMOPATHOGENIC FUNGUS BEAUVERIA-BASSIANA ON CUTICULAR COMPONENTS FROM THE MIGRATORY GRASSHOPPER, MELANOPLUS-SANGUINIPES

The major cuticular components of laboratory reared migratory grasshopper, Melanoplus sanguinipes were characterized in order to test which could be utilized for growth by the entomopathogenic fungus Beauveria bassiana. The major cuticular components were protein, chitin, and lipids. Analysis of lipids from the surface of the cuticle revealed the presence of C14:0-C18:3 fatty acids and other lipids which comprised 7.4% ( wt wt) of the cuticle. Stearic acid (C18:0) was the most abundant fatty acid. Proteins were sequentially extracted with various solvents and classified as water soluble (4.3% wt wt), hydrophobically bound (1.6% wt wt), hydrogen-bound (7.2% wt wt), or covalently bound (48.3% wt wt). Amino acid analysis of the water-soluble proteins showed an abundance of hydrophilic amino acids. Covalently bound proteins were rich in alanine, proline, and other nonbulky, hydrophobic amino acids. Cysteine and methionine were absent in M. sanguinipes cuticle. The removal of proteins from cuticle resulted in a loss of structural integrity as revealed by scanning electron microscopy. Chitin comprised 30.1% ( wt wt) of the cuticle and ash, 1.1% ( wt wt). None of the fatty acids found on M. sanguinipes cuticle were mycocidal toward B. bassiana and variably affected germination and hyphal growth, in vitro. Of the sequentially treated cuticles, poorest germination and hyphal growth was observed on cuticle which had all proteins removed. © 1992.