Meeting Abstract
32.1 Tuesday, Jan. 5 Prey processing in chimaeroid fishes FERRY-GRAHAM, LA*; HUBER, DR; DEAN, M; CLAES, JM; MALLEFET, J; California State Univ.; Univ. of Tampa; Univ. of California Irvine; Univ. Catholique de Louvain; Univ. Catholique de Louvain lfgraham@mlml.calstate.edu
Holocephalans are uniquely derived for durophagy: the upper jaw is fused to the neurocranium (holostyly), and all chimaeriform holocephalans, extinct and extant, possess tooth plates. Yet, for the three extant families, authors have posited that there has been a gradual transition away from a reliance on crushing benthic prey. The Callorhynchidae (Callorhynchus) are the most like ancestral chimaeriforms in their morphology. However, the Chimaeridae (Hydrolagus and Chimaera) are described as being less suited for crushing, and more reliant on suction prey capture. We set out to quantify differences in morphology and performance between these two chimaeriform groups, and specifically to test the hypothesis that Callorhynchus is capable of processing harder prey than Hydrolagus or Chimaera. Cranial and muscular data were collected from a size range (~10 individuals) of Callorhynchus callorhynchus, Hydrolagus colliei, and Chimaera monstrosa. A PCA on external head measurements suggested that there are differences in head shape, but contrary to predictions, Chimaera was different from Callorhynchus and Hydrolagus. However, MANCOVA, used to compare estimated bite forces among the three species, with head width as a covariate, revealed that Callorhynchus tended to differ from Hydrolagus and Chimaera. Additional statistical exploration of the cranial and muscular variables used to generate bite force estimates further supported such performance differences. Interestingly, CT scans of Callorhynchus and Hydrolagus revealed only subtle differences in the amount of skeletal calcification (reinforcement), which was slight in both species. Further, Callorhynchus appears to possess some red adductor musculature, which, if confirmed, yields significantly lower bite force estimates. Thusly, it remains unclear if the chimaeroid feeding paradigm is supported.
