Meeting Abstract
Incredibly invasive Asian carp are destroying ecosystems throughout the United States by outcompeting native species. Their ability to feed so efficiently within eutrophic environments is due to their highly modified gill rakers and complex epibranchial organ. The epibranchial organ is a paired food condensing organ ventral to the neurocranium that has independently evolved multiple times. Ranging in complexity from small slits on the ventral face of the neurocranium to intricate spiraling structures, epibranchial organs are morphologically diverse across filter-feeding fishes. Despite this morphological diversity and broad distribution, little is known of the epibranchial organ’s function and development. Here we present data from an ontogenetic series of Silver carp ranging in size from 15-900mm SL detailing how this unique structure develops. Indeed, the epibranchial organ of the Silver carp is morphologically distinct from all that have been previously described. Gill rakers that extend from branchial arches 1-5 are greatly modified as they curve into the body of the epibranchial organ. Throughout ontogeny the epibranchial organ becomes more complex with the gill rakers becoming increasingly incorporated into the overall structure. Increased complexity coincides with histological changes to supporting cartilaginous structures and an increase in innervation. By early juvenile stages, the epibranchial organ is fully functional. The adult epibranchial organ forms a multiple-looped structure that efficiently moves food from the gill rakers to the pharyngeal jaws. This detailed anatomical investigation has yielded a functional hypothesis of the epibranchial organ in Silver carp.
