Lipid and fatty acid/alcohol compositions of the subarctic copepods Neocalanus cristatus and Eucalanus bungii from various depths in the Oyashio region, western North Pacific

Abstract

Lipids of Neocalanus cristatus and Eucalanus bungii (C3 to adults), collected in March, May, and December from various depths (0-2000 m) were studied in the Oyashio region, western North Pacific. Total lipid and wax ester contents of younger N. cristatus stages increased during the development, being higher in May than in March and December. Major fatty acids of younger N. cristatus were 16:0, 20:5(n−3), and 22:6(n−3) and the dominant alcohols were 16:0, 16:1(n − 7), 20:1(n − 9)/(n −11) and 22:1(n −11). The energy-rich 20:1 and 22:1 moieties increased from the younger to the adult stages showing the importance of lipid biosynthesis which may be advantageous for successful overwintering and reproduction at depth. The 16:4(n − 1) fatty acid, characteristic of a diatom diet increased in May, particularly in the younger stages. Our results suggest that the diatom-dominated feeding mode of younger N. cristatus during the spring bloom is important for an effective accumulation of wax esters. In contrast to N. cristatus, E. bungii accumulated substantial amounts of triacylglycerols. The total lipid and triacylglycerol content increased slightly toward the older developmental stages. The major fatty acids were 16:0, 16:1(n−7), 18:1(n−9) and (n−7), and 20:5(n−3). There was no evidence of developmental or seasonal changes in the fatty acid composition. The differences in the lipid storage modes of both copepods via wax esters or triacylglycerols are species-specific but their fatty acid compositions varied according to diet and developmental stage, especially in N. cristatus. These lipid characteristics are discussed in relation to reproduction, feeding modes, diapause and overwintering strategies.

Taxonomic, Temporal, and Spatial Variations in Zooplankton Fatty Acid Composition in Puget Sound, WA, USA

“…In most taxa, we did not separate life stages, and that potentially confounded seasonal differences as there may be dietary shifts, e.g., increased carnivory with age. Yamada et al (2016) found differences in both lipid content and composition among life stages and seasons of copepods in the western North Pacific, and several studies in polar regions have found strong seasonality in lipids (Kattner et al 1994;Mayzaud et al 2011). However, consistent with our results, Costalago et al (2020) found that season and region had statistically significant but minor effects on zooplankton fatty acid composition in the northern Salish Sea.…”

Seasonal and spatial dynamics of the planktonic trophic biomarkers in the Strait of Georgia (northeast Pacific) and implications for fish

“…Concurrently, this species had one of the lowest δ 15 N values (8.55‰). These results suggest that this species had a diet dominated by phytoplankton, unlike many copepod species that are omnivorous, and may thus be an important, albeit of relatively poor nutritional quality, link between primary producers and the fish that consume these copepods 52 .…”

Zooplankton functional group responses to environmental drivers off the west coast of Vancouver Island, Canada

“…southern and carnivorous species) which may potentially decrease the efficiency of biomass transfer due to higher metabolic rate requirements that lead to higher respiration losses (Palomares and Pauly, 1998;Heilmayer et al, 2004;Pörtner et al, 2012;Barneche and Allen, 2018). Additionally, these southern species may be considered a less desirable prey source as they are usually less lipid-rich than subarctic and boreal-shelf counterparts (Tsuda et al, 2004;Yamada et al, 2016). Therefore, increases in the abundance of non-endemic copepod and gelatinous zooplankton species may increase the functional diversity of the community while simultaneously decreasing the efficiency with which energy is transferred.…”

“…This is particularly important when comparing southern versus boreal-shelf and subarctic copepod group species as well as crustacean versus gelatinous zooplankton. Southern copepod species have been considered less lipid-rich than their northern subarctic NE Pacific counterparts (Tsuda et al, 2004;Yamada et al, 2016). A recent study has highlighted that many gelatinous zooplankton species do not have the same weight-specific energy content when compared to crustacean zooplankton species, with the exception of some Gastropoda and Tunicata species (Lüskow et al, 2021).…”