Abstract
The bowhead whale gastrointestinal system is complex. Similar to their ruminant relatives, as well as their sister taxa Hippopotamidae, the bowhead whale stomach is a multichambered organ and highly distensible to accommodate seasonally abundant and/or patchy prey aggregations. Akin to ruminants and hippos, the first stomach chamber, the forestomach, is a fermentation chamber, but adapted to break down chitin, not cellulose. In contrast to ruminants and hippos, the bowhead whale forestomach is the only nonglandular compartment. For bowheads, digestion begins in the fundic chamber (the second compartment). Although small and often ignored as a stomach chamber, the connecting channel is functionally significant, and serves as a gate keeper to only allow food of the correct particle size to pass in the final compartment, the pyloric chamber. The bowhead whale small intestine has a typical mammalian building plan, but the small intestine to body length ratio is surprisingly short given the nutritional complexities of their zooplankton prey, including chitin armament and abundant wax esters. Similar to other baleen whales, bowheads are efficient wax ester digesters; yet, the exact mechanism of wax ester digestion remains unclear. The bowhead microbiome has recently been characterized, and two microbial taxa are correlated to wax ester abundance in the small intestine, pointing to a possible mechanism. The overall digestive efficiency of bowhead whales is comparable to other baleen whales at about 95%.
Published Version
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