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Dietary availability determines metabolic conversion of long‐chain polyunsaturated fatty acids in spiders: a dual compound‐specific stable isotope approach
Author(s) -
MathieuResuge Margaux,
Pilecky Matthias,
Twining Cornelia W.,
MartinCreuzburg Dominik,
Parmar Tarn Preet,
Vitecek Simon,
Kainz Martin J.
Publication year - 2022
Publication title -
oikos
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.672
H-Index - 179
eISSN - 1600-0706
pISSN - 0030-1299
DOI - 10.1111/oik.08513
Subject(s) - terrestrial plant , polyunsaturated fatty acid , trophic level , biology , terrestrial ecosystem , aquatic ecosystem , aquatic insect , food chain , ecology , aquatic plant , habitat , isotope analysis , fatty acid , ecosystem , macrophyte , biochemistry
Consumers feeding at the aquatic–terrestrial ecosystem interface may obtain a mixture of aquatic and terrestrial diet resources that vary in nutritional composition. However, in lake riparian spiders, the relative significance of aquatic versus terrestrial diet sources remains to be explored. We investigated the trophic transfer of lipids and polyunsaturated fatty acids (PUFA) from emergent aquatic and terrestrial insects to spiders at varying distances from the shoreline of a subalpine lake in Austria, using differences in fatty acid profiles and compound‐specific stable carbon (δ 13 C) and hydrogen (δ 2 H) isotopes. The omega‐3 PUFA content of emergent aquatic insects was higher than that of terrestrial insects. Emergent aquatic insects contained on average 6.6 times more eicosapentaenoic acid (EPA) and 1.2 times more α‐linolenic acid (ALA) than terrestrial insects, whereas terrestrial insects contained on average 2.6 times more linoleic acid (LIN) than emergent aquatic insects. Spiders sampled directly on the lake and in upland habitats had similar EPA contents, but this EPA was derived from different diet sources, depending on the habitat. The δ 13 C EPA and δ 2 H EPA values of ‘lake spiders' revealed an aquatic diet pathway (i.e. EPA of aquatic origin). In contrast, EPA of spiders collected in terrestrial habitats was depleted in both 13 C and 2 H compared to any potential food sources, and their ALA isotopic values, suggesting that EPA was partly bioconverted from its dietary precursor ALA (i.e. internal pathway). The δ 2 H values of fatty acids clearly indicated that diet sources differed depending on the spider's habitat, which was less evident from the δ 13 C values of the fatty acids. Our data highlight that spiders can use two distinct pathways (trophic versus metabolic) to satisfy their physiological EPA demand, depending on habitat use and dietary availability.