Hygrophilous springtails (Arthropoda: Collembola) with different diets are a potential source of eicosapentaenoic fatty acid for terrestrial consumers

Springtails are tiny and inconspicuous, but numerous and diverse arthropods that play a significant role in soil food webs. They inhabit various ecosystems — moist forest floors, freshwater or sea shores, and water surface — and, as a result, have various diets. We hypothesized that habitats affect fatty acid (FA) compositions of springtails: species living near aquatic ecosystems will contain higher levels of physiologically valuable long-chain polyunsaturated fatty acids (LC-PUFAs) of the n-3 family, which are primarily synthesized by aquatic organisms. We studied density and biomass, and FA composition and content of springtails living near water bodies (Halisotoma boneti, Isotomurus palustris, Scutisotoma muriphila) and two species of the genus Pogonognathellus living in the dry bed of a forest stream. According to FA trophic markers the species had different diets that might affect the content of LC-PUFAs. The content of eicosapentaenoic acid (EPA, 20:5n-3) was high in all studied species and varied from 2.2 mg·g⁻¹ of ww in Pogonognathellus spp. from a forest to 3.7 mg·g⁻¹ of ww in I. palustris from a lake shore. The percentage of EPA was 13.1–17.3 % of the total FAs. That is unusual for terrestrial organisms and is comparable to larvae of amphibiotic insects. EPA content in clusters of hygrophilous springtails reached 16.4–44.9 mg·m⁻². Hygrophilous springtails could be a valuable source of EPA for terrestrial consumers. Additionally, we found the effect of the phylogenetic factor on FA profiles: H. boneti from different habitat had similar FA profiles, while representatives of Isotomidae family differed from representatives of Tomoceridae family in FA profiles.