Content area
Full Text
J Chem Ecol (2012) 38:547556 DOI 10.1007/s10886-012-0127-5
Millipedes That Smell Like Bugs: (E)-Alkenals in the Defensive Secretion of the Julid Diplopod Allajulus Dicentrus
Michaela Bodner & Gnther Raspotnig
Received: 14 February 2012 /Revised: 2 April 2012 /Accepted: 7 April 2012 /Published online: 12 May 2012 # Springer Science+Business Media, LLC 2012
Abstract The secretions from serial defensive glands of the Austrian diplopod Allajulus dicentrus (Julidae, Cylindroiulini) were extracted and analyzed by means of gas chromatography mass spectrometry. In adults, 13 components from two chemical classes were detected: 1) The common juliform benzoquinones were represented by four compounds (2-hydroxy-3-methyl-1,4-benzoquinone, 2-methoxy-3-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, and 2,3-dimethoxy-5-methyl-1,4-benzoqui-none). From this series, 2-methoxy-3-methyl-1,4-benzoqui-none was most abundant, comprising about 40 % of the whole secretion. 2) All remaining compounds were identified as aliphatic (E)-alkenals [(E)-2-heptenal, (E)-2-octenal,(E)-2-nonenal, (E)-2-decenal)] along with their corresponding alcohols. (E)-2-Octenal was most abundant, roughly accounting for another 35 % of the secretion. In juveniles, different stages in the ontogenetic development of the secretion were observed, with early instars (stadium III and IV) exclusively containing the benzoquinone fraction. Alkenols and alkenals were added in later instars (stadium V and VI), with secretions of stadium VI-juveniles being already similar to those of adults. Representatives of Spiro-streptida, Spirobolida, and Julida traditionally have been considered to produce benzoquinonic secretions only (qui-none millipedes), and information on secretion components
from other chemical classes is still scarce. We here provide evidence for the participation of non-quinonic compounds in the defensive exudates of the Cylindroiulini. The occurrence of additional, non-quinonic compounds in certain species within a chemically homogenous, benzoquinone-producing taxon indicates the rapid adoption of novel exocrine compounds, possibly in order to meet the demands in a changed ecological environment.
Keywords Quinone diplopods . Chemical defense .(E)-2-octenal . 2-methoxy-3-methyl-1,4-benzoquinone . Juliformia . Julidae . Cylindroiulini.
Introduction
Diplopods are well-known to produce various kinds of defensive secretions that include: 1) unusual alkaloidal compounds in the Glomerida and Polyzoniida; 2) mainly cyanogenic compounds and their breakdown products, including hydrogen cyanide, in the Polydesmida; 3) phenolic compounds in the Callipodida; and 4) particularly, benzoquinone-rich exudates in the Juliformia (Meinwald et al., 1975; Eisner et al., 1978; uri et al., 2009; Makarov et al., 2010; Vujisi et al., 2011; Shear et al., 2011; Shimizu et al., 2012 and references therein). To describe...