Meeting Abstract

P3.16  Saturday, Jan. 5  More than the sum of its parts: Functional development of a complex feeding system within zebrafish STAAB, K.L.*; HERNANDEZ, L.P.; The George Washington University kstaab@gwu.edu

Premaxillary protrusion within Cypriniformes is mediated by a complex system of muscles, ligaments, and bones. This includes the kinethmoid, a novel ossification within the rostral skeleton. Taut ligaments tying together the neurocranium, premaxillae, maxillae and palatines suspend the kinethmoid. Mouth opening and subsequent rotation of the maxilla (effected by contraction of jaw adductors) causes the kinethmoid to rotate and protrude the premaxillae. The origin and evolution of complex functional systems has long been an active area of research within functional morphology. Renewed interest in evolutionary developmental biology has led to an increased research effort investigating the early development and origination of complex systems. Here we investigate the development of kinethmoid-driven premaxillary protrusion to elucidate how a complex system comprised of multiple elements (from disparate embryological origins) develops to form one functional unit. Firstly, there is a novel ossification, the kinethmoid, which rotates about its axis during protrusion of the premaxillae. The kinethmoid first develops as a cartilage within the ligament uniting the paired maxillae. While the kinethmoid is seen early in development, it is not until the juvenile stage that significant premaxillary protrusion is seen. This may be due to the fact that kinethmoid-mediated premaxillary protrusion requires a change to the adductor mandibulae muscles. The adductor mandibulae, the primary lower jaw closing muscle arises early in development as a single unit but later divides into divisions essential for protrusion. Finally, an unprecedented bridge of ligaments suspending the kinethmoid and allowing protrusion must develop properly before protrusion can occur.