Meeting Abstract

34.2  Monday, Jan. 5  The Evolution, Development, and Genetics of Jaw Asymmetry in Lake Tanganyika Scale Eating Cichlids STEWART, T.A.*; ALBERTSON, R.C.; Syracuse University tastew01@syr.edu

Perissodus microlepis, Perissodus straeleni, and Perissodus paradoxus are cichlid fishes native to Lake Tanganyika in central Africa, which forage through lepidophagy, or scale-feeding. Each species is laterally asymmetrical, their heads tending towards either the left or right side of the sagittal plane. These are the most derived species within the Perissodini tribe; their highly specialized morphologies are derived from generalist deepwater predators. Geometric morphometric shape analysis of craniofacial structures was performed to describe both their anatomical basis and the origin of these asymmetries within the Perissodini tribe. Biomechanical models of the oral jawsimple-lever and four-bar linkage modelsindicate that scale eating cichlids show discrete, sided differences in jaw shape, and that these differences predict lateralization in the force and speed of jaw rotation. Morphometric analysis of larval P. microlepis indicates that laterality is determined early in development, before feeding occurs, suggesting a genetic basis for handedness. Furthermore, QTL mapping in Malawi cichlids has identified a single locus of major effect for jaw laterality. We intend to examine the association between this locus and jaw handedness in Lake Tanganyikan scale eaters. Nature is replete with examples of craniofacial asymmetries (i.e., narwals, owls, flatfish), and many human birth defects are characterized by asymmetric craniofacial malformations (hemifacial microsomia, Treacher-Collins syndrome, hemihypertrophy). Studying the evolution of laterality in Perissodus and ultimately identifying the genetic factors that contribute to the asymmetric development of skeletal structures will shed light on the evolutionary and clinical consequences of vertebrate laterality.