Meeting Abstract

81.2  Friday, Jan. 7  Bite force production in Kyphosidae MORAN, C.J.*; FERRY, L.A.; Moss Landing Marine Labs cmoran.mlml@gmail.com

The modeling of force production in fish jaws has been a large area of research in fish ecomorphology. Force production is especially important when diet items are firmly attached to substrate, such as in herbivory. In the north eastern Pacific, temperate herbivory occurs in a few families of fishes despite an enormous untapped herbivorous niche. This study compares the theoretical bite force between two members in the family Kyphosidae; one of the few families that are able to utilize this niche. The opaleye, Girella nigricans possesses an intramandibular joint (IMJ), while the zebraperch, Hermosilla azurea lacks this joint; yet both are benthic feeding herbivores. Output forces were estimated at different angles of closing during the bite in opaleye. Force production was also compared between a ‘regular’ bite, with no flexion at the IMJ, and a bite with flexion. The relative contributions of the primary jaw closing muscles, the Adductor Mandibulae II and Adductor Mandibulae III, were also modeled. We found the opaleye to be a scraping specialist with a high mechanical advantage and high force produced at the tooth bearing surface. In theoretical manipulations, the IMJ did shorten the out-lever, but did not yield a significant increase in force produced. Functionally, the IMJ appears to allow for a larger gape and longer residence time of the tooth-bearing surface on the substrate being scraped. The Adductor Mandibulae II and III are markedly different from one another in both size and angle of attack, yet their contribution to the total out-put force during the bite did not vary. Despite differences in jaw morphology and intramandibular bending we found both temperate herbivorous Kyphosids to be similar in their bite force production.