Unraveling the Mysteries of Velvet Worm Slime
The velvet worm
Nature is full of animals that have developed original defense or predation mechanisms. This is the case of the velvet worm which projects a viscous jet called slime onto its prey. “The particularity of this slime is that it stiffens on contact with air as the prey struggles. It ends up being completely trapped in the trap and the velvet worm can then feed on it,” explains researcher Alexandre Poulhazan (Ph.D. biochemistry, 2022), who became interested in the subject while he was carrying out his doctorate in the research laboratory of the professor of the Department of Chemistry, member of NanoQAM, Isabelle Marcotte.
As co-first author, the graduate wrote an article in the Journal of the American Chemical Society detailing the original molecular structure of this mysterious slime, whose properties could eventually lead to the creation of new synthetic materials.
The velvet worm appeared on Alexandre Poulhazan’s radar in 2017 when Professor Matthew J. Harrington, from McGill University, called on Isabelle Marcotte’s laboratory. “Professor Harrington is collaborating with a team of German researchers from the universities of Leipzig and Kassel who have been interested in the velvet worm for around ten years,” says the biophysicist.
It was the abnormally high presence of phosphorus in the velvet worm slime that prompted Professor Harrington to seek help from his colleague at UQAM. “The research team’s hypothesis was that phosphorus would indicate the presence of phospholipids, a family of fatty substances about which we have developed expertise over the years,” explains Isabelle Marcotte.
In parallel with his thesis which focused on microalgae, Alexandre Poulhazan was entrusted with the mission of uncovering the molecular secrets of velvet worm slime. Research agent and lecturer Alexandre Arnold also participated in the work and is among the co-signatories of the article, as is Isabelle Marcotte.
A unique phenomenon
The velvet worm lives in tropical forests and measures between 1 and 15 centimeters, Alexandre Poulhazan tells us. “It was subdivided about 400 million years ago into two branches, one found in Barbados and the other in Oceania. Even though their colors may differ, both branches have retained the same hunting method. Velvet worms can project their slime up to 10, 20 or 30 centimeters, or even more in some cases.
“To our knowledge, it is the only material projected by an animal which goes from the liquid state to the solid state outside the animal,” marvels Isabelle. Marcotte. By comparison, the spider has glands in which the silk is liquid, and it is through a phenomenon of extrusion, that is to say when the silk passes through very narrow channels, that the molecules reassemble to pass from a liquid state to a solid state. The same goes for mussel byssus, the kneading of which inside a gland creates a fiber which then comes out in solid form. For velvet worm slime, everything happens outside the body of the animal, it’s unique!”
The German team had already demonstrated that the liquid-air interface is crucial in the phenomenon. “If we shake the worm, no fibers will form inside its body,” explains Alexandre Poulhazan. It is absolutely necessary that the liquid is expelled, in contact with the air, and that the prey struggles to stiffen the material.
“Soluble in water, this stiffened slime is “recyclable”, that is to say that the velvet worm recovers the material by eating its prey, a bit like the spider does with its web,” continues Isabelle. Marcotte.
Complex manipulations
When he joined the project, Alexandre Poulhazan thought it would be easy to analyze the slime. “It’s always more complicated than expected in biology,” he says with a laugh. The reason, in this case, is that it is a difficult sample to handle.
The German team went to Barbados to bring back velvet worms and developed a method for harvesting the slime, by putting the animal’s head in a tube. The slime is expelled through ducts called “oral papillae” located on each side of the worm’s mouth, explains Alexandre Poulhazan. A worm produces approximately 20 microliters of slime per attack (one microliter is 0.001 milliliters).
To prepare the sample for analysis in nuclear magnetic resonance, it must be transferred to a suitable container. “Usually we use pipettes to take liquids, but with slime this is impossible, because it creates too much turbulence in the liquid and fibers form. We had to go drop by drop using a small spatula.”
A molecular architecture that could be useful
The first analyzes carried out at UQAM by Alexandre Poulhazan with mass spectrometers and nuclear magnetic resonance devices revealed that these were not phospholipids but phosphonates, which are found mainly in marine animals. and rarely in terrestrial animals. “Analyses of whole worms by nuclear magnetic resonance and transcriptomics have also revealed the presence of phosphonates in different parts of the animal’s body, supporting the thesis of the recycling of its own material,” notes the researcher.
To take the analysis further, Alexandre Poulhazan went to the National High Magnetic Field Laboratory, located in Tallahassee, Florida. “They agreed to welcome me so that I could use a brand new high-sensitivity nuclear magnetic resonance probe which makes it possible to analyze molecules in low abundance without having to use labeling isotopes,” explains the one who continues. currently his postdoctoral studies at Stanford University, California.
Result of these new analyses: the phosphonates in the slime are linked to sugars, which are themselves linked to proteins. “The production of phosphonates – phosphorus linked to a carbon atom – by the velvet worm is a chemical bond that requires a lot of energy,” notes Isabelle. Marcotte. Normally, one would think that with evolution, the animal would have come to synthesize a chemical group that requires less energy. This indicates that there was an evolutionary advantage to continuing to make phosphonates, that they are irreplaceable in the slime “recipe”. The next part of the project is to find out why.”
Even if there are still other research questions to elucidate to better understand the role of phosphonates, we can already envisage the impact of the work carried out so far, adds the professor. “This molecular architecture could eventually lead to the development of new synthetic materials with similar properties,” she illustrates. A story to follow!
Source : Actualités UQAM