Meeting Abstract
The feeding novelties of cypriniform fishes are responsible for the success of this group in freshwater within a variety of ecological niches. The palatal organ (PO) is one of these novelties, a muscular pad located on the pharyngeal roof that is used in feeding. It has been found in all cypriniform fishes that have been examined, despite previous studies that correlated a large vagal lobe with the presence of a palatal organ. Previous research using carp and goldfish has shown that the PO is innervated by the vagus nerve and used for manipulating and sorting through detritus, as well as potentially being used in suction feeding, but despite its importance, a careful study of the early developmental origin and growth has not yet been undertaken. Therefore the zebrafish, Danio rerio, a well-characterized cypriniform model organism, was used to trace the development of the PO through late embryonic, larval, and early juvenile growth as the PO fully develops and is innervated. As the yolk is absorbed and D. rerio switches to exogenous feeding, disorganized fast muscle fibers begin to form between the extraocular muscles at approximately 6 days post fertilization. These fibers grow caudally across the pharyngeal roof towards the branchial arches. The disorganized fibers form a tangled web that may allow the palatal organ to function as a hydrostat capable of forming localized protrusions in multiple directions. These data suggest that from an early age, D. rerio may be using the PO to suction feed and/or manipulate prey items. Understanding the development of the PO will help elucidate how it has become incorporated into the entire feeding apparatus of cypriniform fishes and may also help explain how this group has so successfully invaded so many trophic niches.
