Lipid metabolism by right whales: using fecal samples to assess assimilation of copepod triacylglycerols and wax esters

• Main Authors: NC DOCKS at The University of North Carolina Wilmington, Swaim, Zachary
• Language: English
• Published: 2009
• Subjects: Right whales > Metabolism; Right whales > Research > New Brunswick > Bay of Fundy; Lipids > Analysis; Lipids > Metabolism; Feces > Examination; Calanus finmarchicus; Eubalaena glacialis; Copepods
• Online Access: http://libres.uncg.edu/ir/uncw/f/swaimz2008-1.pdf

In mammals, reproductive health and success are closely linked to nutritional health and body condition, particularly for females. Thus, adequate and reliable food resources are required for populations to remain stable, or to increase. In the Bay of Fundy, right whales (Eubalaena glacialis) feed almost exclusively on stage V copepods, Calanus finmarchicus (C5). Calanus possesses two classes of storage lipids, triacylglycerols (TAG) and wax esters (WE), the latter making up 94% of the total lipid present. Interestingly, most mammals are incapable of metabolizing WE and consequently eliminate WE in their feces. Current energetic models assume that right whales are utilizing all of the lipids from their copepod prey. This study aims to determine whether right whales can metabolize all copepod lipids by comparing estimates of the lipids a right whale consumes with those that are eliminated in the feces. Using data from 60 copepod and 24 fecal samples, a right whale ingestion model and known copepod lipid composition, I estimated that an average right whale (40000 kg) ingests approximately 62000 g of lipid per day. The majority of total lipid ingested (~ 58000 g) consists of WE. Using allometrically-derived estimates of defecation rates in conjunction with the lipid composition of fecal material, I calculated that an average right whale eliminates approximately 250 g of WE per day, implying that right whales are assimilating over 99 % (57765 g) of the ingested WE. The composition of fecal material differed significantly from that of the diet, suggesting that eliminated lipids might originate from a source other than diet. Copepod lipid composition was dominated by long chain saturated fatty acid (FA) components 14:0 (14.73 ± 0.32 wt%) and 16:0 (8.99 ± 0.20 wt%), with monounsaturated and polyunsaturated components comprising the remainder of the FA composition. Long chain monounsaturated 20:1n-9 and 22:1n-11 dominated the fatty alcohol (FAlc) composition. FAlc components comprised only a small portion (< 3.0 ...