Integument

Hydrocarbons of the Chagas disease vector Rhodnius prolixus

M. P. Juárez 1 , G. J. Blomquist 2 , D. R. Carlson 3 and C. J. Schofield 4

1 Instit. Investig. Bioquím. La Plata, Fac. Cs. Méd, UNLP, calles 60 y 120, La Plata 1900, Argentina. 2 Dept. Biochem., Univ. Nevada, Reno, NV 89557, USA. 3 USDA-ARS, Gainesville, Fl 32604, USA and 4 Dept. Infect. Trop. Diseases, LSHTM, London WC1 E7HT, UK

The blood-sucking insect Rhodnius prolixus is the major Chagas disease vector in Venezuela, Colombia and Central America. The surface hydrocarbons were characterized by capillary gas chromatography coupled to mass spectrometry (CGC-MS). Hydrocarbons are important components of the cuticular lipids, and distinctive CGC profiles could be obtained from insect wings. Major components were n-alkanes of C27, C29, C31 and C33 carbons. Adult males and females differ in the relative amounts of their methyl branched chains, mostly among the C29 and C31 mono-, tri- and tetramethyl derivatives. Methyl groups were inserted internally at positions 7-, 11-, 13-, 15- or anteiso for monomethyl isomers, and separated by three or five methylene groups for the trimethyl or tetramethyl derivatives. Heavier molecular weight isomers of 37, 39 and 41 atoms in their carbon esqueleton, with mono-, tri- or tetramethyl branching separated by three and sometimes five methylenes were also identified. The internal hydrocarbon pool contained large amounts of the high molecular weight methyl branched fraction. No major sexual dimorphism was detected for the adult stage, but a significant shift in the major n-alkane components, from n-C27 and n-C29 in the adults to n-C31 and n-C33 in the nymphal stages was evident, together with larger amounts of the higher molecular weight methyl branched chains. Comparison of the hydrocarbon structures to that of other Chagas disease vectors will be discussed.

Index terms: Triatominae, methylalkanes, cuticular lipids, gas chromatography

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