Chemistry of the oil gland secretion of Collohmannia gigantea (Acari: Oribatida)

The chemistry of the lemon-scented oil gland secretion ofCollohmannia gigantea, a middle-derivative mixonomatanoribatid mite, was investigated by gas chromatography – massspectrometry.Gas chromatographic profiles of whole body extracts of C.gigantea revealed two distinct chromatographic zones, the firstcontaining a set of six volatile compounds, comprising the lemon-scentedmonoterpene aldehydes neral and geranial, the scented monoterpene ester nerylformate, a distinctly scented aromatic aldehyde(2-hydroxy-6-methyl-benzaldehyde= 2,6-HMBD), and the two non-scented hydrocarbons, tridecane and pentadecane.All six components appeared to be present in steady relative proportions inscenting mites only, indicating their unity within the scented secretion. Incontrast, the components of the second chromatographic zone were less volatileand found in both, scenting and non-scenting mites. Chemically, they representaset of fatty acids of already known cuticular origin.The secretion bouquet ofthe first chromatographic zone was linked with oil glands by histochemicalmeans: large amounts of aldehydes were present only in oil gland reservoirs,notin any other region of the mite body. While chemical profiles of oil glandsecretions of several dozen astigmatid mites are known, only one other oribatidoil gland composition, from a desmonomatan species, has been elucidated, beingalmost the same as that of C. gigantea. Moreover, allcomponents of these two secretions are widely distributed amongst astigmatidmite species and may also be common in a restricted set of middle-derivativeoribatids. These findings are consistent with the idea of astigmatid miteoriginfrom a mixonomatan-desmonomatan group.