Meeting Abstract
Bat species in the Phyllostomidae family evolved from a common insectivorous ancestor to eat a variety of diets. Evolutionary changes in a species’ diet are accompanied with changes in digestive physiology, including increasing sucrase activity in frugivores and nectivores, and loss of sucrase in sanguivores. Additionally, bats must also meet the high energy requirements of flight, and nectarivores can fuel flight almost exclusively using recently ingested sucrose, glucose or fructose. This feat is not only due to efficient digestion and absorption in bats, but also due to post-absorptive adaptations to increase sugar oxidation to directly fuel their metabolism. However, species-specific adaptations to sugar oxidation have not been investigated. We examined whether capacity for oxidation of sucrose and its components glucose and fructose vary among dietary guilds. We used a carbon stable isotope breath tracer technique to non-invasively monitor the oxidation of 13C enriched sugars (glucose, fructose, and sucrose) over 90 mins using through their breath stable isotope signature. Insectivorous bats had overall lower oxidation rates and no effect of sugar type. In comparison, the lack of sucrase enzyme in vampire bats (Desmodous rotundus) precludes the breakdown of sucrose, preventing its absorption and oxidization. Frugivorous and nectarivorous species had overall higher oxidation rates, with fructose reaching peak oxidation faster. Since glucose and fructose are both partially absorbed through paracellular absorption in bats, the rapid and high rate of fructose absorption could be due to post-absorption adaptions rather than absorption rates. Overall, this study supports known differences in intestinal enzymes, but also suggests additional species-specific adaptations in the oxidation of sugars in bats.
