Oil gland chemistry of Trhypochthonius tectorum (Acari: Oribatida) with reference to the phylogenetic significance of secretion profiles in the Trhypochthoniidae

The oil gland secretion profile of a cosmopolitan oribatid species, Trhypochthonius tectorum (Berlese) (Trhypochthoniidae), was investigated by gas chromatographic - mass spectrometric analyses and is shown to consist of 11 components, comprising four terpenes (neral, geranial, two isomeric farnesals), three hydrocarbons (pentadecane, a heptadecadiene and a heptadecene), two aromatic compounds (2-hydroxy-6-methylbenzaldehyde = 2,6-HMBD, gamma-acaridial = 2-formyl-3-hydroxybenzaldehyde) and two components not yet identified. The stereochemistry of farnesals was partly elucidated, indicating the presence of (Z,?)-farnesal and (E,?)-farnesal, respectively. The unsaturated hydrocarbons were further characterised as 4-heptadecene and 6,9-hepadecadiene. The heptadecadiene and (Z,?)-farnesal represented the most abundant components, followed by 2,6-HMBD and gamma-acaridial. (E,?)-farnesal, 4-heptadecene, pentadecane, neral and geranial were minor components. The oil gland secretion profile of T. tectorum is compared to secretion profiles of trhypochtlioniid species from America and Japan, and possible (chemical) apomorphies of trhypochthoniid genera are discussed.