Meeting Abstract
Elasmobranch (sharks, rays, and skates) olfactory morphology is similar to teleost fishes, but the effects of ontogeny and phylogeny are unclear. Olfactory rosettes are composed of a central raphe that supports repeating lamellae, which are lined with the sensory epithelia. Previous research has shown that lamellar number varies among species, but does not indicate sensitivity to odorants. Habitat has also been correlated with the number of lamellae. The goal of this study was to investigate the relationships among ontogeny, species, and rosette morphology using fineness ratio (2D measure of shape), lamellar count, raphe width, interlamellar distance, and lamellar thickness measurements. The shapes of the rosettes are expected to vary among species due to cranium structure; however the shape should remain constant throughout development. Morphological measurements were collected from five elasmobranch species (N=29 specimens; families Alopiidae, Lamnidae, Carcharhinidae, and Sphyrnidae) with a known body size, measured by fork length (FL). Data was analyzed using mixed model ANOVAs with species, body size (FL), and species * body size (FL) interaction term as effects. We found that olfactory organ fineness ratio, lamellar counts, and raphe width among species was significant. Body size (FL) was not a significant effect for any of the tested variables. The species * body size (FL) interaction term was a significant effect for fineness ratio. Interlamellar distance and lamellar thickness were not significant over a range of sizes and among species. We hypothesize that phylogeny is a key component of olfactory rosette variability. Further research will examine the data using a phylogenetic principal component analysis (pPCA) to examine these relationships.
