CHITIN DIGESTION AND ASSIMILATION BY SEABIRDS

摘要: ABSTRAC.-AS a structural component of crustacean exoskeletons, chitin is the most important carbohydrate in diets many marine carnivores. To investigate physiological and biochemical adaptations that may enable seabirds to break down this "prey defense," we estimated digestibilities for Sooty Albatrosses (Phoebetria fusca), White-chinned Petrels (Procellaria aequinoctialis), Rockhopper Penguins (Eudyptes chrysocome), Gentoo (Pygoscelis papua), King (Aptenodytes patagonicus) Leach's Storm-Petrels (Oceanodroma leucorhoa) fed Antarctic krill (Euphausia superba). These species retain substantial proportion (46.5 ? SD 13.1%, 39.1 4.9%, 52.8 37.6%, 45.3 5.6%, 84.8 11.7% 35 12.2%, respectively) ingested chitin. We also obtained preliminary estimates chitinolytic activity gastric mucosae above six by incubating extracts tissue samples with substrate measuring production end product hydrolysis, N-acetyl-D-glucosamine (NAG). Chitinolytic (up 5,000 ,ug NAG h-l g-1 expressed per gram tissue) was measured from proventricular within range (1,350 61,650 ytg g-1) reported eight other avian species. In order assess energetic nutritional benefits seabirds, studied gastrointestinal absorption products chitinolysis StormPetrels. The overall efficiency its deacetylated precursor, glucosamine (Gln), 44.0 3.0% 11.0 1.9%, respectively. efficiencies were significantly less than glucose, which absorbed an 90.6 2.5%. No Gln occurred proventriculus. Overall, showed have capacity assimilate considerable portion carbon nitrogen present as exoskeleton their prey, but not demonstrated assimilation actually occurs. potential costs well breakdown products, need be assessed. Received 24 May 1991, accepted 18 December 1991.