Fatty acid recovery after starvation: insights into the fatty acid conversion capabilities of a benthic copepod (Copepoda, Harpacticoida)

摘要

Benthic copepods (Harpacticoida) are key members of the meiofauna community, and potentially important conveyers of energy from primary producers to higher trophic levels. However, little is known on their capability for trophic upgrading of food quality (essential fatty acids). Therefore, Platychelipus littoralis copepods were subjected to famine (3 days) and subsequent refeeding (6 days) on high (Thalassiosira weissflogii) and low (Dunaliella tertiolecta) quality food at 4, 15 and 24 C-omicron, and their resilience for recovery of structural and storage fatty acids was determined. Additionally, stable isotope probing of fatty acids gave insight into the copepods' ability to synthesize ARA (20:4 omega 6), EPA (20:5 omega 3) and DHA (22:6 omega 3) from low quality food under different temperatures. High intraspecific variability (among copepod replicates) in fatty acid composition and C-13 enrichment was observed when copepods were exposed to heat (24 C-omicron) and food quality stress, and operated therefore as an indicator of environmental stress. Synthesis of the essential fatty acids ARA, EPA and DHA from dietary precursors increased with temperature. However, despite the capability for synthesis, no fatty acid accumulation was observed, which suggested substantial fatty acid turnover, especially under heat stress. Moreover, synthesis rates were not sufficient to restore the omega 3 pools and ensure survival, at least for the duration of the experiment. Therefore, the question rises whether copepods of this local P. littoralis population will be able to cope with the reduced dietary supply of essential omega 3 fatty acids, as predicted under global warming, given that the physiological need for these essential compounds likely increases with temperature.