Meeting Abstract
Sharks, uniformly accepted as carnivores, have guts specialized for a high-protein diet. However, the bonnethead shark (Sphyrna tiburo) has been shown to consume copious amounts of seagrass (up to 62.1% of gut content mass). Bonnetheads were found to digest 51.2% of the organic matter in seagrass, as well as possess cellulose-component-degrading enzymes (β-glucosidase) in their hindguts. This indicates likely involvement from the gut microbiome as part of the seagrass digestion process. In order to understand the role that the microbiome plays in bonnethead shark seagrass digestion, gut contents and mucosal scrapings were collected along the digestive tract of wild-caught bonnetheads (n=4) and bonnetheads that were fed a 90% seagrass and 10% squid diet in the lab (n=5). Using 16s rDNA sequencing, we determined the taxa of microbes present along the bonnethead shark digestive tract. Using gas chromatography of gut content fluid, we determined the concentrations of short-chain fatty acids, the primary end-products of microbial fermentation, in the different gut regions. Data collection is in progress. Results of this work show that the bonnethead shark is digesting seagrass at higher efficiency than would be expected for a “carnivore,” and digestion may be aided by microbial symbionts. These findings have ecological implications because they show that bonnethead sharks are omnivorous and play a different role (including nutrient transport) than assumed within fragile seagrass ecosystems.
