title: Fall Composition of Storage Lipids is Associated with the Overwintering Strategy of Daphnia.
abstract: Diapause, which occurs through the production of dormant eggs, is a strategy used by some zooplankton to avoid winter months of persistent low temperatures and low food availability. However, reports of active zooplankton under the ice indicate that other strategies also exist. This study was aimed at evaluating whether the composition of storage lipids in the fall differs between diapausing and active overwintering Daphnia. We assessed the quantity of storage lipids and fatty acid (FA) composition of Daphnia species, along with FA content of seston, in six boreal, alpine and subarctic lakes at the onset of winter, and evaluated the association between storage lipids and Daphnia overwintering strategy. We found that active overwintering Daphnia had >55% body fat and the highest FA concentrations. Polyunsaturated FA, especially stearidonic acid (18:4n-3; SDA) and high ratios of n-3:n-6, were preferentially retained to a greater extent in active overwintering Daphnia than in those that entered diapause. Daphnia FA composition was independent of that of the seston diet, indicating that Daphnia adjusted their storage lipids according to the physiological requirements of a given overwintering strategy. The occurrence of an active overwintering strategy has consequences for zooplankton community structure, and can have important implications for the transfer of high-quality energy at higher trophic levels.
authors.affiliation: Department of Environmental and Biological Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland. heather.mariash@gmail.com.|Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Québec, G7H 2B1, Canada. heather.mariash@gmail.com.|National Wildlife Research Centre, Science and Technology Division, Environment and Climate Change Canada, Carleton University, 1125 Colonel By Dr., Ottawa, ON, K1A 0H3, Canada. heather.mariash@gmail.com.
authors.forename: Heather L
authors.initials: HL
authors.lastname: Mariash
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Québec, G7H 2B1, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Cusson
authors.affiliation: Department of Environmental and Biological Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.|Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Québec, G7H 2B1, Canada.|Centre for Northern Studies (CEN), Université Laval, Quebec, QC, Canada.|Group for Interuniversity Research in Limnology and Aquatic Environment (GRIL), Université of Montréal, Montreal, QC, Canada.
authors.forename: Milla
authors.initials: M
authors.lastname: Rautio
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry; D000818:Animals; D003621:Daphnia / Q000737:chemistry / Q000502:physiology*; D005227:Fatty Acids / Q000032:analysis*; D005247:Feeding Behavior; D012621:Seasons; D015048:Zooplankton / Q000737:chemistry / Q000502:physiology*
chemical_list: D005227:Fatty Acids
keywords: Fatty acids; Freshwater; Ice; Life history strategies; SDA; Winter; Zooplankton