Alkaloid chemistry in pill-millipedes: Defensive secretion in two species of Typhloglomeris Verhoeff, 1898 (Diplopoda, Glomerida, Glomeridellidae)

Millipedes of the order Glomerida are known to produce quinazolinone alkaloids as defensive substances. However, chemical data are rather scarce and all hitherto available publications refer to a single glomeridan family, the Glomeridae. To contribute to the knowledge of the chemical ecology of glomeridans, we collected species, Typhloglomeris coeca Verhoeff, 1898 and T. varunae Makarov, Lučić, Tomić Karaman, 2003, from a second family – Glomeridellidae. The defensive exudates were extracted in methylene chloride and analyzed by gas chromatography-mass spectrometry. Our results show that the secretions of the two glomeridellids contain the quinazolinone alkaloid homoglomerin (2-ethyl-1-methylquinazolin-4(1H)-one) as the sole defensive constituent. This report provides initial data on the chemoprofiles of members of the family Glomeridellidae and supports the phenomenon of chemical homogeneity of glomeridan defensive secretions. So far, all analyzed representatives of the order possess glomerin and/or homoglomerin as defensive equipment. The phylogenetic origin of alkaloidal compounds in the secretions of millipedes in general, and particularly the origin of quinazolinone alkaloids in Glomerida is discussed. Considering that the quinazolinone alkaloid defensive secretions may be the same (or very similar) in other Glomerida, our results have important implication for further studies of defensive secretions in these arthropods. Also, as data are available only for a limited number of glomeridan and colobognathan species, additional analyses are necessary to elucidate the evolution of alkaloid defensive secretion in Diplopoda.