Identification of electrophysiologically-active compounds for New World screwworm, Cochliomyia hominivorax, in larval wound fluid.
Acidic and non-acidic fractions from extracts of fluid from sheep wounds infested with larvae of Cochliomyia hominivorax (Coquerel) were analysed by linked gas chromatography and electroantennography in order to detect electrophysiologically-active compounds that could be potential attractants. Responses to twenty-six electrophysiologically-active compounds were observed and, on the basis of electron impact and chemical ionization mass spectrometry and co-chromatography with authentic compounds, twenty-five of these compounds were characterized. The most abundant compounds identified in the larval wound fluid were straight and methyl-branched aliphatic carboxylic acids, ranging from C2- to C5-carbon chain length. Butanoic acid, for example, was found to be present at approximately 0.45 mg/ml. Aliphatic carboxylic acids with longer chain lengths were also observed but in trace amounts. Three aromatic carboxylic acids, benzoic, phenylethanoic and 3-phenylpropanoic acids were also present but only phenylethanoic and 3-phenylpropanoic acids elicited electroantennographic responses. Phenol and indole were by far the most abundant components of the non-acid fraction of the larval wound fluid with all other components, except delta-valerolactam, present at levels of less than 5% that of phenol which was present at a concentration of 0.05 mg/ml. Electroantennographic studies of straight-chain aliphatic carboxylic acids showed that pentanoic acid elicited the strongest response from C. hominivorax. Similar studies showed that 1-octen-3-ol elicited stronger responses than 3-methylphenol, indole, phenol or dimethyldisulphide. 3-Methylindole, which was not found in the wound fluid, also elicited a strong response. The potential behavioural significance of these compounds is discussed in relation to that of known attractants of C. hominivorax and other dipteran pests of mammals.
Natural Resources Institute, Chatham Maritime, Kent, U.K.
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D000438:Alcohols / Q000302:isolation & purification* / Q000494:pharmacology; D000818:Animals; D002264:Carboxylic Acids / Q000302:isolation & purification* / Q000494:pharmacology; D002630:Chemotactic Factors / Q000302:isolation & purification* / Q000494:pharmacology; D002849:Chromatography, Gas; D004175:Diptera / Q000502:physiology; D004478:Ectoparasitic Infestations / Q000473:pathology / Q000503:physiopathology / Q000662:veterinary*; D005122:Exudates and Transudates / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D007814:Larva; D011679:Pupa; D012610:Screw Worm Infection / Q000473:pathology / Q000503:physiopathology / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases
D000438:Alcohols; D002264:Carboxylic Acids; D002630:Chemotactic Factors