Xibalbanus tulumensis, a venomous remipede found in anchialine caves on the Yucatán Peninsula, is the only crustacean for which a venom system has been described.
Xibalbanus tulumensis. Image credit: Pinheiro-Junior et al., doi: 10.1186/s12915-024-01955-5.
“Venomous animals inject their toxic compounds into other organisms primarily for self-defense or predation,” said Dr. Björn von Reumont, a researcher at Goethe University Frankfurt, and his colleagues.
“Numerous venoms comprise proteins that have evolved to modulate a range of physiological functions in their target organisms.”
“Investigating these bioactivities may lead to pharmacological or agrochemical applications.”
“The majority of venoms and venom proteins that have been thoroughly studied mainly originate from iconic and terrestrial groups such as snakes, spiders, scorpions, and insects,” they said.
“Marine species have received limited research attention, with only a small number of fish and invertebrate species — such as sea anemones, jellyfish, cone snails, cephalopods, polychaetes, and recently nemerteans — being better studied.”
“As venoms and their toxic proteins have independently evolved in various animal lineages, researching new lineages presents on the one hand an opportunity to identify novel venom compounds with interesting bioactivity and on the other hand to enhance our understanding of the evolution of convergent functional traits generally.”
In their study, the researchers investigated the bioactivity of peptides found in venom of the crustacean species Xibalbanus tulumensis.
This underwater cave-dwelling crustacean belongs to the class Remipedia, which was first described in the 1980s and currently comprises 28 living species.
“Xibalbanus tulumensis lives in the cenotes which are the underwater cave systems on the Mexican Yucatan peninsula,” the scientists said.
“The cave dweller injects the venom produced in its venom gland directly into its prey.”
“This toxin contains a variety of components, including a new type of peptide, named xibalbine, after its crustacean producer.”
“Some of these xibalbines contain a characteristic structural element that is familiar from other toxins, especially those produced by spiders: several amino acids (cysteines) of the peptide are bound to each other in such a manner that they form a knot-like structure.”
“This in turn makes the peptides resistant to enzymes, heat and extreme pH values.”
“Such knottins often act as neurotoxins, interacting with ion channels and paralyzing prey — an effect that has also been proposed for some xibalbines.”
The study shows that all the xibalbine peptides tested by the team — and in particular Xib1, Xib2 and Xib13 — effectively inhibit potassium channels in mammalian systems.
“This inhibition is greatly important when it comes to developing drugs for a range of neurological diseases, including epilepsy,” Dr. von Reumont said.
“Xib1 and Xib13 also exhibit the ability to inhibit voltage-gated sodium channels, such as those found in nerve or heart muscle cells.”
“In addition, in the sensory neurons of higher mammals, the two peptides can activate two proteins — kinases PKA-II and ERK1/2 — involved in signal transduction.”
“The latter suggests that they are involved in pain sensitization, which opens up new approaches in pain therapy.”
The team’s findings were published in the journal BMC Biology.
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E.L. Pinheiro-Junior et al. 2024. Diversely evolved xibalbin variants from remipede venom inhibit potassium channels and activate PKA-II and Erk1/2 signaling. BMC Biol 22, 164; doi: 10.1186/s12915-024-01955-5
