The Chemistry of Millipede Defense Secretions

Jenn Hoskins
10th June, 2024

The Chemistry of Millipede Defense Secretions

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Virginia Tech studied the chemical defenses of three Brachycybe millipede species
  • They identified five alkaloids, including three new ones: hydrogosodesmine, homogosodesmine, and homo-hydrogosodesmine
  • The chemical diversity of these compounds aligns with the millipedes' evolutionary relationships, not their geographic locations
Millipedes are fascinating creatures known for their diverse chemical defenses, which help them deter predators. These compounds, stored in specialized glands called ozadenes, are released when the millipede feels threatened. The subclass Colobognatha, which includes four orders of millipedes, is particularly noteworthy for producing terpenoid alkaloids, except for the Siphonophorida that produce terpenes. Despite their intriguing structures, these compounds have been the least studied among millipede defensive secretions. A recent study conducted by researchers at Virginia Tech[1] delves into the chemical defenses of three Brachycybe species: Brachycybe producta, Brachycybe petasata, and Brachycybe rosea. The study employed advanced analytical techniques such as mass spectrometry-based metabolomics, chemical synthesis, and 2D NMR to identify five alkaloids, three of which are new to the scientific literature. These newly identified compounds include indolizidine (hydrogosodesmine) and quinolizidine alkaloids (homogosodesmine and homo-hydrogosodesmine). Interestingly, the chemical diversity of these compounds aligns with the known phylogeny of the Brachycybe genus, rather than the geographical proximity of the species. This finding is particularly significant because it suggests that these millipedes generate their complex defensive agents de novo, shedding light on the evolution of their biochemical pathways. For instance, the indolizidines and quinolizidines are produced by non-sympatric sister species, B. producta and B. petasata, while another set of non-sympatric sister species, B. rosea and Brachycybe lecontii, produce deoxybuzonamine. The study's findings build on previous research that has highlighted the chemical complexity of millipede defensive secretions. For example, a prior study identified gosodesmine, a unique alkaloid with some terpene character, from the millipede Gosodesmus claremontus[2]. This was the first report of an alkaloid from a platydesmid millipede and the first report of a 7-substituted indolizidine from an arthropod. The current study expands this knowledge by identifying new alkaloids and linking their diversity to the millipedes' phylogeny. Moreover, the study's approach to understanding millipede chemical defenses through phylogenetic relationships rather than geographic proximity addresses a significant gap in the field. Previous research has shown that millipede classification and species diversity estimates are often unreliable due to inconsistent taxonomic efforts and geographic biases[3]. By focusing on phylogenetic relationships, the current study provides a more accurate framework for understanding the evolution of chemical defenses in millipedes. The findings also have broader implications for the study of chemical defenses in other arthropods. For instance, dendrobatid poison frogs accumulate alkaloids from their diet into their skin as a defense mechanism against predators[4]. The evolutionary development of specific enzymes in these frogs enhances the potency of these alkaloids. Similarly, the current study suggests that millipedes may have evolved specific biochemical pathways to produce their complex defensive agents. In conclusion, the study conducted by Virginia Tech provides valuable insights into the chemical defenses of Brachycybe millipedes, identifying new alkaloids and linking their diversity to the species' phylogeny. This research not only expands our understanding of millipede chemical ecology but also offers a more accurate framework for studying the evolution of chemical defenses in other arthropods.

BiochemAnimal ScienceEvolution

References

Main Study

1) The Chemistry of the Defensive Secretions of Three Species of Millipedes in the Genus Brachycybe

Published 10th June, 2024

https://doi.org/10.1007/s10886-024-01518-6

Related Studies

2) Gosodesmine, a 7-Substituted Hexahydroindolizine from the Millipede Gosodesmus claremontus.

https://doi.org/10.1021/acs.jnatprod.0c00722

3) Millipede taxonomy after 250 years: classification and taxonomic practices in a mega-diverse yet understudied arthropod group.

https://doi.org/10.1371/journal.pone.0037240

4) Evidence for an enantioselective pumiliotoxin 7-hydroxylase in dendrobatid poison frogs of the genus Dendrobates.

Journal: Proceedings of the National Academy of Sciences of the United States of America, Issue: Vol 100, Issue 19, Sep 2003


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