Acetates in secretions of thrips
Tschuch G1, Lindemann P2 Moritz G1
1Developmental Biology, Department of Biology, 2Phamaceutical Biology, Department of Pharmacy, Martin-Luther-University Halle-Wittenberg, D-06099 Halle, Germany.
Correspondence: tschuch@zoologie.uni-halle.de
Secretions of Thysanoptera species consist of very different chemical constituents, such as aliphatic hydrocarbons, carboxylic acids, aliphatic esters, cyclic esters of hydroxyl carboxylic acids (lactones), pyranones, naphthoquinones, and terpenes. In this paper, only aliphatic esters of acetic acid, found in 30% of the investigated species, are the focus of attention. The aliphatic ester with longest chain known previously from Thysanoptera is octadecyl acetate from Gynaikothrips uzeli, only 2.2 % of secretion (Suzuki T et al. 1989. Japanese Journal of Applied Entomology and Zoology 24: 222每228). Hexadecyl acetate is reported from Gynaikothrips ficorum and G. uzeli where it is one of the main constituents, and in smaller amounts from Leeuwenia (=Varshneyia) pasaniae and from Liothrips kuwanai (Howard DF et al. 1987. Phytophaga 1: 163每170; Suzuki T et al. 1988. Japanese Journal of Applied Entomology and Zoology 23: 291每297). A small part of the Liothrips kuwanai secretion (1.2 %) is probably hexadecenyl acetate (double bond position unknown). The secretion of L. pasaniae contains mainly tetradecyl acetate (15.4 %), tridecane (51.3 %), and pentadecane (12.4 %). In contrast to these species of Tubulifera, the only species of Terebrantia from which chemicals have been identified so far, Frankliniella occidentalis, produce a mixture of dodecyl and decyl acetate in the anal droplets of second instar larvae, although only in traces in secretions by adults (Teerling CR et al. 1993. Journal of Chemical Ecology 19: 681每697.). The recently investigated defensive secretions of adult and larval Suocerathrips linguis (Phlaeothripidae, Thysanoptera) were found to contain a long chained acetate, (11Z)-11,19-eicosadienyl acetate, that was not previously known to occur naturally (Csuk R et al. 2004. Tetrahedron 60: 6001每6004; Tschuch G et al. 2005. Journal of Chemical Ecology 31: 1555每1565). This substance occurred together with octadecyl acetate and other long chained acetates. The eicosadienyl acetate repels ants and spreads on the surface of such potential predators. The mixture can provide a liquid long-lasting surface coating with a very low vapour pressure. In predators like ants and mites, using mainly the olfactory sense, coating the sensory organs would make the animals ※blind§. They would not be able to find the prey again, and ants would have difficulty evaluating their own pheromones, such as trail pheromones to return to the nest and inform nest-mates about potential prey.
