What’s foul-tempered, has translucent skin, and bites its prey with venomous copper jaws? It’s the bloodworm, a delightfully freaky wriggler that measures about 15 inches long and has puzzled scientists for decades with its bizarre metal teeth.
In addition to earning their creepy name for their equally creepy see-through skin, which exposes the hemoglobin in their blood, these worms harvest copper from their environment to strengthen their jaws for combat and carnivory.
Now, scientists led by William Wonderly, a graduate student at the University of California Santa Barbara, have solved some of the open questions about how and why these animals evolved this mouthful of copper. The results identified the crucial role of a specific multi-tasking protein (MTP) in the “impressive wear resistance” of bloodworm jaws, a finding that holds “tremendous potential for bio-inspired and natural materials processing,” according to a study published on Monday in the journal Matter.
Wonderly is the latest in a line of researchers who have worked with these temperamental worms at UCSB’s Waite Lab, led by biochemist Herbert Waite, who is the senior author of the study. Since the 1980s, Waite has overseen many discoveries about the incredible properties of bloodworm jaws, but Wonderly was particularly interested in the role of melanin, a type of pigment, as a major component of these unusual body parts.
“This is amazing because there are very few examples in nature of melanin being used as a load-bearing material grown at millimeter length scales!” Wonderly said in an email. “When I joined the Waite Lab, I had recently read Frank Herbert’s Dune, so I jumped at the opportunity to work with real life sand worms.”
“The question that intrigued me the most was—how do these worms grow melanin at such a large lengthscales?” he added. “Proteins are a hugely important component in how biological organisms template and synthesize materials, so finding the protein used in bloodworm jaws may help us understand how to unlock novel strategies for melanin synthesis.”
All animals have some metals circulating in their bodies, but the fang-like jaws of bloodworms contain “significant quantities of copper (up to 10% by weight),” reports the new study. Likewise, other organisms have been observed using “ionic copper in a variety of contexts,” Wonderly noted, though “there are none that I am aware of that store copper mineral—particularly atacamite—in a load-bearing material.”
The way these animals deploy these metal-reinforced jaws in the wild is like something out of an otherworldly horror movie: The worms turn their digestive system inside-out and launch an appendage, called an eversible proboscis, at their prey. Their venomous four-pronged fangs can puncture through hard-shelled mollusks and crustaceans, efficiently killing these animals. Bloodworms are also easily provoked into battle with members of their own species, and their sudden strikes can even send humans to the hospital with severe allergic reactions.
“They certainly are vicious!” Wonderly confirmed. “They are burrowing worms that use an eversible proboscis to attack their prey. They are opportunistic eaters and respond to their environment through sensors on the tip of their nose. When their sensors are triggered, they will evert their proboscis to expose their jaws and clamp down on whatever they can find.”
“What makes matters worse is that they are one of only a few marine worms that inject venom into their prey,” he continued. “The whole situation reminds me of something from the movie Alien,” adding that “fortunately, I was never bitten by one, but they certainly never stopped trying.”
While avoiding the bad moods of these trigger-happy worms, Wonderly and his colleagues conducted “state-of-the-art transcriptomic methods,” which is a type of gene sequencing, on specimens of the species Glycera dibranchiata acquired from the Bloodworm Depot, a bait dealer in Maine, according to the study.
With this approach, the study was able to reconstruct the intricate part that a multi-tasking protein (MTP) plays in attracting and processing copper from the worms’ environment. The protein achieves these ends “by assuming unprecedented roles as a building block, organizer, and fabricator—a processing feat of considerable relevance to the autonomous production of other polymer composites, blends, and/or networks,” the researchers said in the study. As a result, understanding this protein, and its interactions in the bloodworm jaw system, has implications for material science.
“The most exciting thing to me are the opportunities provided by a novel method of melanin synthesis,” Wonderly explained. “Melanin is a material with very intriguing mechanical, optical, and semiconducting properties, but there are significant synthetic challenges associated with melanin. In a biological context, Glycera worms are able to grow melanin at the millimeter length scale, and our preliminary experiments with these proteins indicate an interesting process that produces thin, melanized films.”
“Furthermore, I’m really interested in the protein itself,” he continued. “Most of the highly functional proteins used in nature have complicated sequences that organize themselves into complicated structures. The proteins used in Glycera jaws, on the other hand, almost exclusively use two amino acids—glycine and histidine. This really lends itself to creating synthetic analogs that could mimic what the Glycera jaw proteins can do.”
In this way, the team’s identification of this special protein has opened a window into the full process behind the development of the animal’s characteristic bite, which has enabled it to become a force of nature in its seabed environment.
But though the study has shed new light on the terrifying jaws of the bloodworm, there are still many secrets to be unlocked about these animals, including the exact role of copper in catalyzing their venom. To that end, scientists will have to bear the disagreeable temperaments of these unique creatures in future experiments to better understand their amazing abilities.
Update: This article has been updated with comments from lead author William Wonderly.