AUTHOR=Raspotnig Günther , Hüfner Antje , Bodner Michaela , Blesl Julia , Schaider Miriam , Escalante Ignacio , Kunert Olaf 

TITLE=Polymorphic scent gland secretions in Nelima harvestmen: “Sclerosomatid compounds” but different chemical lineages

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2022.993368

DOI=10.3389/fevo.2022.993368

ISSN=2296-701X

ABSTRACT=<p>The scent glands of harvestmen (Opiliones) produce secretions of taxon-specific composition. One class of compounds, assumed to be a key group in opilionid chemosystematics and prevalent among sclerosomatid Eupnoi, was termed “sclerosomatid compounds” (SCs). Known compounds of this group comprise acyclic 4-methyl-branched ethyl-ketones and -alcohols as well as 2,4-dimethyl-branched primary alcohols and aldehydes, originally described from several species of North American Leiobuninae. We analyzed the scent gland secretions of <italic>Nelima</italic> ssp. (Sclerosomatidae, Leiobuninae) from two continents by gas chromatography-mass spectrometry, NMR, stereoselective synthesis, and chiral chromatography. We found a surprising chemical dichotomy: while North American <italic>N. paesserli</italic> produced typical acyclic SCs such as (<italic>E</italic>)-4-methyl-4-hexen-3-one, the secretions of European <italic>Nelima</italic> species exhibited a mixture of aromatic and aliphatic compounds, namely (<italic>R</italic>)-2-methyl-1-phenyl-pentan-3-one (MPP), 4-phenyl-2-butanone (PB), 2-phenylacetamide (PA), as well as (2<italic>R</italic>,4<italic>R</italic>)-2,4-dimethylhexanoic acid (DHA), all of which are new for the secretions of harvestmen. Remarkably, in <italic>N. sempronii</italic>, the secretions of juveniles (containing PB) differed from the secretions of adults (containing MPP and DHA). Though the chemistry of European <italic>Nelima</italic> species clearly diverged at first sight, all compounds detected either possess specific chemical motifs that allow an assignment to the class of SCs or appear to be biochemically/ontogenetically connected to SC-components. Thus, we here add novel compounds to the pool of SCs along with an extension of the definition of SCs to include aromatic compounds with SC-motifs. Furthermore, we describe a first case of juvenile-adult polymorphism for the exocrine secretions of harvestmen and provide a scheme of how secretions are regenerated.</p>