Selective Fatty Acid Retention and Turnover in the Freshwater Amphipod Pallaseopsis quadrispinosa

Abstract

Gammarid amphipods are a crucial link connecting primary producers with secondary consumers, but little is known about their nutritional ecology. Here we asked how starvation and subsequent feeding on different nutritional quality algae influences fatty acid retention, compound-specific isotopic carbon fractionation, and biosynthesis of ω-3 and ω-6 polyunsaturated fatty acids (PUFA) in the relict gammarid amphipod Pallaseopsis quadrispinosa. The fatty acid profiles of P. quadrispinosa closely matched with those of the dietary green algae after only seven days of refeeding, whereas fatty acid patterns of P. quadrispinosa were less consistent with those of the diatom diet. This was mainly due to P. quadrispinosa suffering energy limitation in the diatom treatment which initiated the metabolization of 16:1ω7 and partly 18:1ω9 for energy, but retained high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) similar to those found in wild-caught organisms. Moreover, α-linolenic acid (ALA) from green algae was mainly stored and not allocated to membranes at high levels nor biosynthesized to EPA. The arachidonic acid (ARA) content in membrane was much lower than EPA and P. quadrispinosa was able to biosynthesize long-chain ω-6 PUFA from linoleic acid (LA). Our experiment revealed that diet quality has a great impact on fatty acid biosynthesis, retention and turnover in this consumer.

Arachidonic acid matters

“…It has been demonstrated that Daphnia can biosynthesize ARA from the elongation/desaturation of 18:2–6 and 18:3–6 55–59 and as well from the retro‐conversion of 22:5n‐6 60,61 . Similar ARA biosynthesis was also observed in copepods 62,63 and amphipods 64 . However, this biosynthetic activity seemed to be not sufficient to support the normal growth and survival of live preys 65,66 .…”

“…60,61 Similar ARA biosynthesis was also observed in copepods 62,63 and amphipods. 64 However, this biosynthetic activity seemed to be not sufficient to support the normal growth and survival of live preys. 65,66 An appropriate ARA dietary supply is still required in live preys.…”

The second life of terrestrial and plastic carbon as nutritionally valuable food for aquatic consumers

“…Lipids were extracted from the filters, zooplankton, and fish according to Folch et al (1957). Samples were fractionated and methylated as Taipale et al (2021). Fatty acid methyl esters were identified and quantified as previously published (Taipale, Hiltunen, et al, 2016).…”

What we do in the dark: Prevalence of omnivorous feeding activity in Arctic zooplankton during polar night

“…We instead found relatively higher contributions of 16:1(n‐7) in the January pelagic A. glacialis . Fatty acid turnover for A. glacialis is unknown, but in a benthic freshwater gammarid amphipod, Pallaseopsis quadrispinosa , turnover for 16:1(n‐7) was higher than for other fatty acids, suggesting a rapid assimilation of this fatty acid from a diatom‐fed diet (Taipale et al 2021). During November/December in the northern Barents Sea, 16:1(n‐7) proportion was in fact low (mean, 7%) in both iPOM and pPOM (Kohlbach et al 2021).…”