Abstract
Heterotrophic protists play pivotal roles in aquatic ecosystems by transferring matter and energy, including lipids, from primary producers to higher trophic predators. Using Oxyrrhis marina as a model organism, changes to the non-saponifiable protist lipids were investigated under satiation and starvation conditions. During active feeding on the alga Cryptomonas sp., the O. marina hexane soluble non-saponifiable fraction lipid profile reflected its food source with the observed presence of long chain mono-unsaturated fatty alcohols up to C25:1. Evidence of trophic upgrading in O. marina was observed with long chain mono-unsaturated fatty alcohol accumulation of up to C35:1. To the best of our knowledge, this is the first evidence that heterotrophic dinoflagellates are capable of producing ester derived alcohols and that dinoflagellates like O. marina are capable of synthesizing fatty alcohols up to C35. Additionally, we show evidence of trophic upgrading of lipids. During a 20-day resource deprivation, the lipid profile remained constant. During starvation, the mobilization of wax esters as energy stores was observed with long chain fatty alcohols mobilized first. Changes in lipid class profile and utilization of wax esters in O. marina provides insight into the types of lipids available for energy demand, the transfer of lipids through the base of marine food webs, and the catabolic response induced by resource deprivation.
Highlights
Heterotrophic dinoflagellates are ubiquitous, important components of the pelagic protozoan community
To the best of our knowledge, this is the first evidence that heterotrophic dinoflagellates are capable of producing ester derived alcohols and that dinoflagellates like O. marina are capable of synthesizing fatty alcohols up to C35, compared to zooplankton species from arctic waters where mono-unsaturated fatty alcohols up to C22 have been observed (Sargent, Gatten & McIntosh, 1977; Wakeham, 1982)
We have provided evidence that during starvation in O. marina that wax esters are mobilized as energy stores while the ratio of polar:non-polar lipids remain constant as cell volume decreases
Summary
Heterotrophic dinoflagellates are ubiquitous, important components of the pelagic protozoan community. Heterotrophic protists add biochemical value during trophic transfer, little is known about how cellular composition changes in response to food availability. These changes in biomass can impact higher trophic levels through changes in cellular composition. Starvation of O. marina for up to 3 weeks resulted in a reduction in cell volume of 17–57% with some cells deformed and transparent (Menden-Deuer et al, 2005) It has been puzzling how a single celled heterotrophic organism can sustain survival in the absence of substantive organic matter, over such extended periods
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