FRANCIS, JR., A. W.*; Saint Joseph’s University: Feeding Functional Morphology and Biomechanics of Southern Flounder, Paralichthys lethostigma

An ontogenetic series of Paralichthys lethostigma was collected from aquaculture facilities and subsequently cleared and double stained for bone and cartilage. From photomicrographs of cleared and stained larvae, measurements were made of head shape, eye migration, quadratal angle, and lower jaw mechanical advantage. These measurements were used to determine stage and/or side specific changes with metamorphosis (eye migration) from bilaterally symmetrical to asymmetrical. Head shape, as determined by the proportion of head depth to head length, remained relatively constant throughout development (~1.0). Quadratal angle, a measure of the relative position of the articular-quadrate joint, changed rapidly from 40° to a maximum of 80° in premetamorphic larvae. This rapid change in position of the articular-quadrate joint suggests that lower jaw depression and elevation changed from a hyoid to opercular based mechanism. With metamorphosis, quadratal angle remained relatively constant, only increasing from 72° to 84° over several orders of magnitude in size. These changes predict differences in lower jaw depression and elevation between premetamorphic, metamorphic, and juvenile stages. Biomechanical measurements of closing in-lever, opening in-lever, and out-lever as well as mechanical advantage for lower jaw elevation were all bilaterally asymmetrical (P < 0.001, 0.005 ≤ α ≤ 0.05). Differences between sides of the head were attributed to longer moment arms on the blind side. Because mechanical advantage for lower jaw depression was not directionally asymmetrical (P = 0.722, α = 0.05), functional asymmetry was not predicted for P. lethostigma.