"EPA and DHA are not typically found in terrestrial insects but usually make up a significant proportion of the total fatty acids in aquatic insects [Sushchik et al., 2003; Gladyshev et al., 2011; Zinchenko et al., 2014]. It has been speculated that aquatic insects may serve an important function in transferring long chain omega-3 fatty acids from aquatic to terrestrial environments [Gladyshev et al., 2011]. The increased levels of both LNA and EPA means the omega-6:omega-3 fatty acid ratio of these insects is much lower than previously reported (crickets 5 vs. 39; mealworms 19 vs. 25; superworms 6 vs. 30, and waxworms 4 vs. 14) [Finke, 2002]. "
[Show abstract][Hide abstract] ABSTRACT: Emerging aquatic insects, including mosquitoes, are known to transfer to terrestrial ecosystems specific essential biochemicals, such as polyunsaturated fatty acids (PUFA). We studied fatty acid (FA) composition and contents of dominant mosquito populations (Diptera: Culicidae), that is, Anopheles messeae, Ochlerotatus caspius, Oc. flavescens, Oc. euedes, Oc. subdiversus, Oc. cataphylla, and Aedes cinereus, inhabited a steppe wetland of a temperate climate zone to fill up the gap in their lipid knowledge. The polar lipid and triacylglycerol fractions of larvae and adults were compared. In most studied mosquito species, we first found and identified a number of short-chain PUFA, for example, prominent 14:2n-6 and 14:3n-3, which were not earlier documented in living organisms. These PUFA, although occurred in low levels in adult mosquitoes, can be potentially used as markers of mosquito biomass in terrestrial food webs. We hypothesize that these acids might be synthesized (or retroconverted) by the mosquitoes. Using FA trophic markers accumulated in triacylglycerols, trophic relations of the mosquitoes were accessed. The larval diet comprised green algae, cryptophytes, and dinoflagellates and provided the mosquitoes with essential n-3 PUFA, linolenic, and eicosapentaenoic acids. As a result, both larvae and adults of the studied mosquitoes had comparatively high content of the essential PUFA. Comparison of FA proportions in polar lipids versus storage lipids shown that during mosquito metamorphosis transfer of essential eicosapentaenoic and arachidonic acids from the reserve in storage lipids of larvae to functional polar lipids in adults occurred.
[Show abstract][Hide abstract] ABSTRACT: Most omnivorous animals, including humans, have to some degree relied on physiologically important polyunsaturated fatty acids (PUFA), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from food. Only some taxa of microalgae, rather than higher plants can synthesize de novo high amounts of EPA and DHA. Once synthesized by microalgae, PUFA are transferred through trophic chain to organisms of higher levels. Thus, aquatic ecosystems play the unique role in the Biosphere as the principal source of EPA and DHA for most omnivorous animals, including inhabitants of terrestrial ecosystems. PUFA are transferred from aquatic to terrestrial ecosystems through riparian predators, drift of carrion and seaweeds, emergence of amphibiotic insects, and water birds. The essential PUFA are transferred through trophic chains with about twice higher efficiency than bulk carbon. Thereby, PUFA are accumulated, rather than diluted in biomass of organisms of higher trophic levels, e.g., in fish. Mankind is faced with a severe deficiency of EPA and DHA in diet. Although additional sources of PUFA supply for humans, such as aquaculture, biotechnology of microorganisms and transgenic terrestrial oil-seed producing plants are developed, natural fish production of aquatic ecosystems will remain one of the main sources of EPA and DHA for humans. Aquatic ecosystems have to be protected from anthropogenic impacts, such as eutrophication, pollution and warming, which reduce PUFA production.
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