Arctic | Mammals
Who is responsible for lipid digestion in bowhead whales: Is it the whale or its gut microbes? Presenter: Carolyn Miller , cmiller@whoi.edu, Woods Hole Oceanographic Institution Mallory Kastner , mallory.kastner@whoi.edu, Woods Hole Oceanographic Institution Helen Fredricks , hfredricks@whoi.edu, Woods Hole Oceanographic Institution Lara Horstmann , lara.horstmann@alaska.edu, University of Alaska Fairbanks Raphaela Stimmelmayr , raphaela.stimmelmayr@north-slope.org, North Slope Borough, Department of Wildlife Management Benjamin Van Mooy , bvanmooy@whoi.edu, Woods Hole Oceanographic Institution Amy Apprill , aapprill@whoi.edu, Woods Hole Oceanographic Institution Lipids are the primary source of energy for baleen whales and are critical for reproduction and survival. The predominant lipids consumed by bowhead whales ( Balaena mysticetus ) are wax esters but how they digest and assimilate wax esters is poorly understood. Our previous study indicated wax esters are digested in the mid-small intestine (jejunum) of bowhead whales and that gut microbes may play a role. Here we tested whether wax esters are hydrolyzed solely by the whale, its gut microbes or a combination of the two by incubating freshly collected gastrointestinal samples with a traceable wax ester at 33.8°C (core temperature of bowhead whales) for 12 - 18 hrs. Whale digestive enzymes and intestinal contents were collected from the hepatopancreatic duct and the lumen of the jejunum, respectively, of nine whales during the Native subsistence harvests in fall 2021 and 2022 in Utqiaġvik, AK. Intestinal contents were split into two incubations, one left untreated such that it contained live microbes and the other treated with paraformaldehyde or antibiotics to kill the microbes. Microbial community composition of intestinal contents will be compared before and after incubations for each treatment by sequencing bacterial and archaeal 16S ribosomal RNA genes. Lipids extracted from incubated samples were quantified using gas chromatography-mass spectrometry. Preliminary results from two whales showed wax ester hydrolysis in intestinal contents with live microbes, but not in contents in which the microbes were killed. Wax ester hydrolysis also was observed in incubations of whale digestive fluid. These preliminary results suggest both the whale and its gut microbiome contribute to the hydrolysis of wax esters, a lipid of considerable importance to the ocean ecosystem and to baleen whale nutrition. Knowledge gained from these results will add to the understanding of the health and ecology of bowhead whales.
Alaska Marine Science Symposium 2023 284
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