On the enigmatic scent glands of dyspnoan harvestmen (Arachnida, Opiliones): first evidence for the production of volatile secretions

Abstract

While considerable knowledge on the chemistry of the scent gland secretions from the opilionid suborders Laniatores and Cyphophthalmi has been compiled, it is the Palpatores (Eupnoi and Dyspnoi) where chemical data are scarce. In particular, the Dyspnoi have remained nearly unstudied, mainly due to their reported general reluctance to release secretions as well as to the phenomenon of production of insoluble—and inaccessible—solid secretion. We here show that at least certain nemastomatid Dyspnoi, namely all three species of genus Carinostoma, indeed produce a volatile secretion, comprising octan-3-one, 6-methyl-5-hepten-2-one and acetophenone in species-specific combinations. In all Carinostoma spp., these volatiles are embedded in a semi-volatile, naphthoquinone matrix (mainly 1,4-naphthoquinone and 6-methyl-1,4-naphthoquinone). In detail, acetophenone and traces of naphthoquinones characterize the secretions of Carinostoma carinatum. A mixture of octan-3-one, 6-methyl-5-hepten-2-one and large amounts of naphthoquinones were found in C. elegans, and 6-methyl-5-hepten-2-one together with small amounts of naphthoquinones in the secretions of C. ornatum. So far, exclusively naphthoquinones had been reported from a single dyspnoan hitherto studied, Paranemastoma quadripunctatum.

The Scent Glands of the Neotropical Harvestman Discocyrtus pectnifemur: Morphology, Behavior and Chemistry

“…Therefore, we propose that hydroquinones and their respective benzoquinones should be considered synonymous, if used for phylogenetic purposes. The identification of defensive compounds from the suborders Cyphophthalmi (Jones et al 2009;Raspotnig et al 2005Raspotnig et al , 2012 and Dyspnoi (Raspotnig et al 2010(Raspotnig et al , 2014bSchaider et al 2011) has allowed more precise inferences about the evolution of the defensive secretions in Opiliones (e.g., Raspotnig et al 2014a). As pointed out by these authors, knowing the biosynthetic routes of the defensive secretion is important because it allows a more realistic use of chemical data for phylogenetic purposes (e.g., proposing weight matrices).…”

“…Finally, the morphology of the ozopore and surroundings, the mode of emission, and the compounds present in the secretion have all been used in the phylogenetic reconstruction of the order Opiliones (Caetano and Machado 2013;Hara and Gnaspini 2003;Raspotnig et al 2014b). Therefore, new information on these features might be useful for resolving phylogenetic problems or proposing synapomorphies for some groups.…”

Chemosystematics in the Opiliones (Arachnida): a comment on the evolutionary history of alkylphenols and benzoquinones in the scent gland secretions of Laniatores

“…As opilionids are an ancient group of arachnids with fossils known from the Lower Devonian (Dunlop et al., ), scent glands represent a well‐suited model for studying the evolution of exocrine secretion chemistry in a homologous gland system across hundreds of millions of years. So far, the secretion chemistry in all four opilionid suborders has been exemplarily investigated, revealing sets of naphthoquinones and methyl ketones in the Cyphophthalmi (Raspotnig et al., , ), naphthoquinones in phalangiid Eupnoi (Wiemer et al., ) and in Dyspnoi (Raspotnig et al., ), various acycles, including ethyl ketones in sclerosomatid Eupnoi (Ekpa et al., ), and volatile ketones in several Dyspnoi (Raspotnig et al., ). The chemically best‐studied group, however, is certainly the Laniatores, from which at least four major chemical classes of secretion components have been reported: (1) nitrogen‐containing compounds including various tobacco alkaloids from travunioid Insidiatores (Raspotnig et al., ), and an array of (2) alkylphenols, (3) benzoquinones and (4) vinyl‐ketones from the Grassatores (Roach et al., ; Duffield et al., ; Eisner et al., ; Hara et al., ; Wouters et al., ).…”

Multi-trait mimicry of ants by a parasitoid wasp

“…3 ). Spectral comparisons with published literature and spectral databases of known compounds (Massbank, Massbank Project) indicated a consistency with 6-methyl-5-hepten-2-one, an unsaturated terpenoid 22 , also known as sulcatone. Fragmentation data of this emission generated by gas chromatography-mass spectrometry (GC-MS) exhibited a high degree of similarity with the spectral fragmentation and retention time of a standard preparation of 6-methyl-5-hepten-2-one (Sigma-Aldrich) injected during analysis ( Figs.…”