Insects provide essential fatty acids to other animals

Life, as we know it, relies on the balance of energy and essential nutrients. Omega-3 and omega-6 polyunsaturated fatty acids (PUFA), found in insects and arachnids, play a critical role in this equilibrium.

These organisms are particularly crucial to birds, hedgehogs, and lizards, although the advantages hinge heavily on the kind of insects and spiders consumed.

Insects with fatty acids

You may be surprised to learn that aquatic insects like dragonflies or caddisflies are richer in omega-3 long-chain PUFA than their land-based counterparts.

Why? The base of the food chain in aquatic ecosystems is algae that are rich in omega-3 LC-PUFA.

Fatty acids pile up in food chains. Take mayflies, for instance, which consume the algae and are subsequently eaten by fish. The mayfly tends to contain more fatty acids than the algae it feeds on; however, the fish that preys on mayflies often has even more.

There are a plethora of studies on this topic, as well as those exploring how plant or algal biodiversity impacts the biomass in ecosystems.

Biodiversity, insects, and fatty acids

Cornelia Twining is the leader of the Food Web Ecophysiology group at the aquatic research institute Eawag and a professor at ETH Zurich.

“Unfortunately, knowledge about how insect and arachnid biodiversity might influence the availability of fatty acids in a food web is rather scant,” said Twining. She, alongside her colleagues, is working hard to bridge this knowledge gap.

Land use and nutrient availability

Based on data including over half a million observations of approximately 7,600 insect and spider species across Switzerland, the research spanned 400 aquatic ecosystems and 300 terrestrial ecosystems.

These ecosystems varied in terms of land usage, ranging from natural habitats such as meadows and forests to city-center sites and agricultural areas.

“We were interested in how land use shapes energy and nutrient availability and whether there are key differences between aquatic and terrestrial ecosystems,” said Ryan Shipley, researcher at the WSL institute for snow and avalanche research SLF and lead author on the study.

“Land use change ranks among the most urgent global challenges, making it essential to understand how human activities impact fundamental ecosystem functions.”

Fatty acid content in insects

The data analysis showed that in the studied communities, a decrease in insect and spider biodiversity resulted in a decline in biomass and key fatty acids content.

“In terrestrial communities, we also see significant differences depending on land use,” said Twining. Even when biodiversity is the same, insect and spider communities in a city park typically provide fewer omega-3 LC-PUFA than those in a forested area.

“This is partly due to the different species composition of these populations, and partly because the biomass is smaller in urban areas: there are also fewer predators like spiders or large beetles, which accumulate LC-PUFA in terrestrial systems,” explained Twining.

Land use and aquatic ecosystems

What came as a surprise to scientists was that the land use effect is much less pronounced in aquatic communities.

On land, the differences are more stark if predators like spiders, which accumulate high amounts of essential fatty acids, vanish from the ecosystem, the impact is substantial. “Yet, this does not imply that the diversity of aquatic insects is not equally important,” Twining stresses.

Aquatic organisms are crucial sources of fatty acids for terrestrial food webs. In urban areas, where loss of insects and spiders is high due to increased human land use pressure, aquatic insects become an even more important source of essential fatty acids for birds, bats, or lizards.

But these important “superfoods” are often tainted with pollutants in streams, rivers, and lakes.

Importance of protecting biodiversity

“Our study shows how important it is to protect biodiversity, especially in agricultural and urban areas, and to improve water quality in order to preserve food webs for ecosystem functioning,” said Twining.

The research contributes to the Blue-Green Biodiversity Research Initiative – an Eawag-WSL collaboration focusing on biodiversity at the interface of aquatic and terrestrial ecosystems.

Funded by the ETH Board, the initiative reminds us why biodiversity is so crucial to the interconnectedness of our natural world.

So, next time you swat away a persistent fly or squash a crawling spider, remember, they’re an essential link in the food chain, providing valuable nutrients for a multitude of creatures, including ourselves.

The study is published in the journal Science.

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