Meeting Abstract
Cypriniforms dominate the Earth’s fresh water systems and possess several evolutionary novelties, many of which are associated with feeding. One such novelty is the palatal organ, a fleshy pad attached to the roof of the buccal cavity. In goldfish and carp, where this structure has been most thoroughly studied, the palatal organ is used to sort food from sediment during bottom feeding. In other species, the structure is greatly reduced and its function is unclear although it has been found in all Cypriniforms examined thus far. There has been little ontogenetic work done on the palatal organ in any species. Moreover, given that it has been suggested that the palatal organ does not exist in zebrafish, little effort has gone into documenting its early development in this popular model species. Here we use the Cypriniform and model organism Danio rerio to investigate the muscle and nerve development of this novel feeding structure. The palatal organ begins development at 60 hours post-fertilization (hpf) as fast skeletal muscle fibers appearing near the posterior of the buccal cavity. From 60 hpf to 84 hpf, muscle fibers move up toward the anterior of the buccal cavity and begin to thicken. During this period of anterior movement, the disorganized muscle fibers anchor themselves to the gill musculature from posterior to anterior. By 6 days post-fertilization the palatal organ is heavily innervated and is in an anatomical position similar to that seen in the adult. These results indicate much earlier muscle development and innervation than was originally thought. Understanding the earliest development of the palatal organ, specifically where this structure first arises in development, can inform us about how this feeding novelty may have arisen during the course of evolution.
