Meeting Abstract

P1.110  Wednesday, Jan. 4  Morphological variation in the palatal organ of Cypriniformes COSTANTINI, KE*; HERNANDEZ, LP; George Washington University phernand@gwu.edu

Cypriniform fishes are characterized by a number of trophic novelties that likely played an important role in the success of the group. These novelties include a unique mechanism of premaxillary protrusion, hypertrophied lower pharyngeal jaws, loss of upper pharyngeal jaw elements, and a muscular palatal organ. The palatal organ is a dorsal mass of muscle fibers within the buccal cavity that is strongly tied to the branchial elements laterally. Previous work on goldfish has shown that this muscular pad is incredibly well innervated and produces localized protrusions that are used to capture edible items while bottom feeding. While the neurobiology and physiology of palatal organ function in the goldfish has been well described, there is little data on palatal organ functional morphology across Cypriniformes. Indeed, previous reports have suggested that this important feeding structure is only found within Catostomidae and a few cyprinids. Many assume that the function of the palatal organ is conserved and as in goldfish, it is only used to selectively feed on the benthos. We suggest that the palatal organ may have become adapted for different purposes in feeding during the course of cypriniform evolution. However before testing such hypotheses we must first analyze the anatomical structure of the palatal organ in a diverse group of cypriniforms. Here we investigate the size, structure, and myosin composition of palatal organs of species within 8 subfamilies. Contrary to published results we found that nearly all species examined have some type of palatal organ. Although not as well developed or highly innervated as that of goldfish, a complex mesh of predominantly fast muscle fibers characterized all cypriniform palatal organs.