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.
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Natural Resources Institute, Chatham Maritime, Kent, U.K.
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