title: Chemical Ecology of Cave-Dwelling Millipedes: Defensive Secretions of the Typhloiulini (Diplopoda, Julida, Julidae).
abstract: Cave animals live under highly constant ecological conditions and in permanent darkness, and many evolutionary adaptations of cave-dwellers have been triggered by their specific environment. A similar "cave effect" leading to pronounced chemical interactions under such conditions may be assumed, but the chemoecology of troglobionts is mostly unknown. We investigated the defensive chemistry of a largely cave-dwelling julid group, the controversial tribe "Typhloiulini", and we included some cave-dwelling and some endogean representatives. While chemical defense in juliform diplopods is known to be highly uniform, and mainly based on methyl- and methoxy-substituted benzoquinones, the defensive secretions of typhloiulines contained ethyl-benzoquinones and related compounds. Interestingly, ethyl-benzoquinones were found in some, but not all cave-dwelling typhloiulines, and some non-cave dwellers also contained these compounds. On the other hand, ethyl-benzoquinones were not detected in troglobiont nor in endogean typhloiuline outgroups. In order to explain the taxonomic pattern of ethyl-benzoquinone occurrence, and to unravel whether a cave-effect triggered ethyl-benzoquinone evolution, we classed the "Typhloiulini" investigated here within a phylogenetic framework of julid taxa, and traced the evolutionary history of ethyl-benzoquinones in typhloiulines in relation to cave-dwelling. The results indicated a cave-independent evolution of ethyl-substituted benzoquinones, indicating the absence of a "cave effect" on the secretions of troglobiont Typhloiulini. Ethyl-benzoquinones probably evolved early in an epi- or endogean ancestor of a clade including several, but not all Typhloiulus (basically comprising a taxonomic entity known as "Typhloiulus sensu stricto") and Serboiulus. Ethyl-benzoquinones are proposed as novel and valuable chemical characters for julid systematics.
authors.affiliation: Institute of Zoology, University of Belgrade - Faculty of Biology, Studentski Trg 16, Belgrade, 11000, Serbia.
authors.forename: Slobodan E
authors.initials: SE
authors.lastname: Makarov
authors.affiliation: Institute of Zoology, University of Graz, Universitätsplatz 2, 8010, Graz, Austria.
authors.forename: Michaela
authors.initials: M
authors.lastname: Bodner
authors.affiliation: Institute of Zoology, University of Graz, Universitätsplatz 2, 8010, Graz, Austria.
authors.forename: Doris
authors.initials: D
authors.lastname: Reineke
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia.
authors.forename: Ljubodrag V
authors.initials: LV
authors.lastname: Vujisić
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia.
authors.forename: Marina M
authors.initials: MM
authors.lastname: Todosijević
authors.affiliation: Institute of Zoology, University of Belgrade - Faculty of Biology, Studentski Trg 16, Belgrade, 11000, Serbia.
authors.forename: Dragan Ž
authors.initials: DŽ
authors.lastname: Antić
authors.affiliation: Institute of Biodiversity and Ecosystem Research, Department of Animal Diversity and Resources, Bulgarian Academy of Sciences, 2 Gagarin Street, 1113, Sofia, Bulgaria.
authors.forename: Boyan
authors.initials: B
authors.lastname: Vagalinski
authors.affiliation: Institute of Zoology, University of Belgrade - Faculty of Biology, Studentski Trg 16, Belgrade, 11000, Serbia.
authors.forename: Luka R
authors.initials: LR
authors.lastname: Lučić
authors.affiliation: Institute of Zoology, University of Belgrade - Faculty of Biology, Studentski Trg 16, Belgrade, 11000, Serbia.
authors.forename: Bojan M
authors.initials: BM
authors.lastname: Mitić
authors.affiliation: Department of Zoology and Anthropology, Sofia University "St. Kliment Ohridsky", Sofia, Bulgaria.
authors.forename: Plamen
authors.initials: P
authors.lastname: Mitov
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia.
authors.forename: Boban D
authors.initials: BD
authors.lastname: Anđelković
authors.affiliation: Institute of Zoology, University of Belgrade - Faculty of Biology, Studentski Trg 16, Belgrade, 11000, Serbia.
authors.forename: Sofija Pavković
authors.initials: SP
authors.lastname: Lucić
authors.affiliation: Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia.
authors.forename: Vlatka
authors.initials: V
authors.lastname: Vajs
authors.affiliation: Institute of Zoology, University of Belgrade - Faculty of Biology, Studentski Trg 16, Belgrade, 11000, Serbia.
authors.forename: Vladimir T
authors.initials: VT
authors.lastname: Tomić
authors.affiliation: Institute of Zoology, University of Graz, Universitätsplatz 2, 8010, Graz, Austria. guenther.raspotnig@uni-graz.at.|Research Unit of Osteology and Analytical Mass Spectrometry, Medical University, Children's Hospital, Auenbruggerplatz 30, 8036, Graz, Austria. guenther.raspotnig@uni-graz.at.
authors.forename: Günther
authors.identifier: http://orcid.org/0000-0002-6947-9406
authors.initials: G
authors.lastname: Raspotnig
mesh_terms: D000818:Animals; D001181:Arthropods / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D016227:Benzoquinones / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D005075:Biological Evolution; D059552:Caves; D017753:Ecosystem; D008401:Gas Chromatography-Mass Spectrometry; D010802:Phylogeny; D052616:Solid Phase Extraction
chemical_list: D016227:Benzoquinones
keywords: 2-ethyl-1,4-benzoquinone; Lamellotyphlus; Serboiulus; Typhloiulini; Typhloiulus; chemical defense; chemosystematics; quinone millipedes