In the paper published in the prestigious Scientific Reports, a team led by Dr. Irena Vardić Smrzlić, Dr. Vlatka Filipović, Dr. Tatjana Mijošek Pavin, and PhD candidate Sara Šariri from IRB conducted the first transcriptomic analysis of this parasite.

Put simply, the scientists examined in detail which genes this species uses when exposed to metals in its environment. They went further, analyzing the potential protein products encoded by those genes, especially those that, based on similarity to proteins in other organisms, are thought to bind metals such as zinc, iron, nickel, and copper. Such proteins are known for helping organisms defend against toxic substances and environmental stress, suggesting they could play a key role in this parasite as well. Although this has not yet been directly confirmed for D. truttae, this research provides the first insight into the possible molecular mechanisms that help it survive in polluted conditions.

A Genetic “Shield” for Survival in Pollution

“The scientific community has long known that acanthocephalans can ‘absorb’ metals from the environment and accumulate them in their tissues,” explains lead author Sara Šariri, a PhD candidate in the Laboratory for Biological Effects of Metals at IRB’s Division for Marine and Environmental Research. “But the mechanism of this process was a complete mystery, and our work is the first step toward understanding exactly how they do it and why they’re so successful.”

The researchers identified which genes the parasite activates in environments with elevated metal concentrations, pinpointed more than 1,900 metal‑binding proteins for zinc, iron, nickel, and copper, and discovered specific protein groups that could serve as biomarkers of environmental stress and detoxification.

Dentitruncus truttae

“High representation of zinc‑finger proteins was expected given their known role in gene expression regulation,” says Dr. Irena Vardić Smrzlić, corresponding author from the Laboratory for Aquaculture and Pathology of Aquatic Organisms at IRB, “but their presence in this parasite further underscores the complex adaptation mechanisms to stressful conditions, and thanks to such gene regulators, D. truttae can probably accumulate high metal levels and survive in environments that would be lethal for most other organisms.”

Beyond their own metal uptake, these parasites may also protect their fish hosts. “In earlier studies, we demonstrated that fish infected with acanthocephalans accumulate lower levels of toxic metals than uninfected fish,” explains Dr. Tatjana Mijošek Pavin, “and this raises fascinating questions about the parasites’ ecological role and the possibility of using them as live sensors for pollution in freshwater ecosystems.”

First in the World to Decode Its Genes

Until now, only a single acanthocephalan species out of nearly 1,300 had its genome and transcriptome published, making these findings a remarkable scientific breakthrough. Such work deepens our understanding of parasite evolutionary biology and paves the way for developing molecular tools, such as qPCR panels that measure activation of specific parasite genes to indicate metal exposure levels in contaminated waters.

“These data lay the groundwork for further research on how organisms cope with metal uptake,” says Dr. Vlatka Filipović Marijić, corresponding author from the Laboratory for Biological Effects of Metals, “and our group is among the few worldwide to introduce acanthocephalans as indicators of environmental status, and we’re recognized in the field of environmental parasitology. Now we’re asking: if these parasites protect their fish hosts from metal overload, can we view them in a more nuanced light rather than solely as harmful?”

In an era where climate change and water pollution are among the greatest global threats, parasites such as Dentitruncus truttae might play an unexpected role in environmental monitoring. Their ability not only to survive but also to shield their hosts from excessive metal exposure suggests fascinating biological resilience and untapped potential for nature conservation.