Why is it important to save parasites as well?

The study published in the ‘Proceedings of the National Academy of Sciences’‘represents the largest dataset in the world on the abundance of parasites in wildlife. The main result is parasites are “especially vulnerable to a changing climate”.

“Most people think that climate change will cause parasites to thrive, that as the world warms we will see an increase in parasite outbreaks,” said lead author Chelsea Wood, a UW professor of aquatic and fisheries sciences.

“This may be true for some parasite species, but because they are host dependent, they are particularly vulnerable in a warming world.” Among those most affected are those connected to several hosts..

For parasites that depend on three or more host species throughout their lifecycle, including more than half of the parasite species identified in study fish, analysis of historical fish samples showed an average decrease of 11% per decade. For this reason, Nine out of ten parasite species that disappeared completely in 1980 were dependent on three or more hosts..

Worrying for ecosystems

“Our results show that parasites with one or two host species remained fairly stable, but three or more host species collapsed,” Wood said. “The degree of decline was severe. If this occurs in species that humans care about, such as mammals or birds, it triggers conservation action.”

Although parasites may cause fear or disgust, especially in those who associate them with their own illness, children or pets, the result is “worrying news for ecosystemssaid wood.

“What we do know is that complex life cycle parasites play an important role in diverting energy through food webs and supporting the largest predators,” says Wood, who is also one of the authors of the 2020 report, which lays out a parasite protection plan.

Wood’s work is a New method to ‘resurrect’ knowledge of past parasite populations. Mammals and birds are protected using taxidermy, which keeps the parasites on skin, feathers or fur only. Fish, reptile and amphibian specimens are preserved in the liquid, which also protects the parasites that live in the animal at the time of its death..

Researchers took fish samples kept in natural history museums and checked for parasites present. Among the multicellular parasites they found were arthropods, including crustaceans, and what Wood described as “incredibly beautiful tapeworms”: Trypanorhyncha, whose heads are armed with hook-covered tentacles. In total, the team counted 17,259 parasites from 85 species in 699 fish samples.

The warmth of the sea, guilty

To explain the reduction in parasites, The authors considered three possible causes: abundance of host species, pollution levels, and ocean surface temperature.. The variable that best explained the reduction in parasites was the latter. Between 1950 and 2019, the sea surface temperature increased by one degree in the study area.

“An interference that requires multiple hosts is like a delicate Rube Goldberg machine,” explains Wood. “The complex series of steps they go through to complete their lifecycle makes them vulnerable to outages at any point along the way.“, detail the authors of the investigation.

“This study shows that There was a significant reduction in parasites. At Puget Sound. If it can go unnoticed in such a well-studied ecosystem, where else could it be?” asks Wood. The authors fear it’s common across the planet.

“I hope our work will inspire other ecologists to think about their focal ecosystems, identify the right museum specimens, and see if these trends are unique to Puget Sound or are happening elsewhere,” he says.

“Our result draws attention to:Parasitic species may be in real dangerWood adds. “And this could mean something bad for human beingsNot only will there be fewer worms, but also fewer parasite-derived ecosystem services on which we have become dependent.”

Reference work: https://www.pnas.org/doi/10.1073/pnas.2211903120