Imagine darkness. A deeper saltwater area of an underwater cave system in the Mexican jungle, which is via subterranean cracks and tubes connected to the sea, but also interlinked with surface freshwater. We cave dive in a Cenote on the Yucatan, deep down in the flooded Mayan underworld. Here dwells, next to holy human remains, a most peculiar crustacean that looks like a garden centipede in a white swimsuit.

Collecting remipeds by cave diving in a Cenote ©BMvR

Xibalbanus tulumensis, however, features not only a peculiar biology, no, it stands also out out from evolutionary aspects. Remipedia, the crustacean class it belongs to, was recently confirmed as key taxon to understand arthropod evolution and success of the most species-rich arthropod group, the insects. New, mainly phylogenomic analyses support that remipedes share a common ancestor with insects forming the group pancrustaceans that unites insects and crustaceans (von Reumont etal. 2012, Misof etal. 2014, Schwendtner etal. 2017). These cave beasties killed, metaphorically speaking, one former contrasting central hypothesis in arthropod evolution, namely that insects are related to myriapods.

The remipede Xibalbanus tulumensis ©BMvR

Apropos killing, Xibalbanus shows even more exciting (r)evolutionary features. Anecdotal evidence reported, partly based on their centipede like body and fang shape, that remipedes might be venomous. Utilizing transcriptomics, proteomics and functional 3D morphology the venom and delivery system of the first venomous crustacean, Xibalbanus tulumensis was recently described (von Reumont etal. 2014, 2017).

Key references

• Reumont, Bjoern M von, Ronald A Jenner, Matthew A Wills, Emiliano Dell’Ampio, Günther Pass, Ingo Ebersberger, Benjamin Meyer, et al. ‘Pancrustacean Phylogeny in the Light of New Phylogenomic Data: Support for Remipedia as the Possible Sister Group of Hexapoda.’ Molecular Biology and Evolution 29, no. 3 (March 2012): 1031–1045.

• Misof, Bernhard, Shanlin Liu, Karen Meusemann, Ralph S Peters, Alexander Donath, Christoph Mayer, Paul B Frandsen, et al. ‘Phylogenomics Resolves the Timing and Pattern of Insect Evolution.’ Science 346, no. 6210 (November 2014): 763–767.

• Schwentner, Martin, David J Combosch, Joey Pakes Nelson, and Gonzalo Giribet. ‘A Phylogenomic Solution to the Origin of Insects by Resolving Crustacean-Hexapod Relationships.’ Current Biology : CB 27, no. 12 (June 2017): 1818–1824.e5.

• Reumont, BjOrn M von, Alexander Blanke, Sandy Richter, Fernando Alvarez, Christoph Bleidorn, and Ronald A Jenner. ‘The First Venomous Crustacean Revealed by Transcriptomics and Functional Morphology: Remipede Venom Glands Express a Unique Toxin Cocktail Dominated by Enzymes and a Neurotoxin.’ Molecular Biology and Evolution 31, no. 1 (January 2014): 48–58.

• Reumont, Bjoern M von, Eivind A B Undheim, Robin-Tobias Jauss, and Ronald A Jenner. ‘Venomics of Remipede Crustaceans Reveals Novel Peptide Diversity and Illuminates the Venom’s Biological Role.’ Toxins 9, no. 8 (July 2017): 1–25.