Stabilizing selection on the variability of spacing of Lobodon carcinophaga (crabeater seal) postcanine teeth for successful filter-feeding foraging strategies

• Main Author: Pollak, Megan
• Other Authors: Tate-Jones, Kellum
• Format: Conference Object
• Language: English
• Published: University of Oregon 2020
• Subjects: Crabeater seal; Postcanine; Pinniped; Stabilizing selection; Filter-feed; Crabeater Seal; Erignathus barbatus; walrus*
• Online Access: https://scholarsbank.uoregon.edu/xmlui/handle/1794/25512

Project files are comprised of 1 page pdf and presentation recording in mp4 format. Pinnipeds, the group that includes true seals, eared seals, and walruses, generally display highly variable tooth spacing. Previous studies have credited this variability to the typical pinniped feeding mechanism, a combination of suction feeding and pierce feeding known as the “grab-and-gulp” method, which does not require precise dental occlusion. However, the crabeater seal (Lobodon carcinophaga) is unique among pinnipeds as an obligate filter-feeder with a diet consisting of mainly krill. The distinct sieve-like postcanine teeth feature high-cuspation and intricate trellis-like morphology, which allows L. carcinophaga to effectively strain small krill from the water. We hypothesize that there is a strong selective pressure from this feeding ecology for postcanine occlusion in the crabeater seal. To test the variability in crabeater seal tooth spacing compared to that of generalist bearded seals (Erignathus barbatus), we measured the tooth gaps between the postcanine teeth of 21 adult specimens of L. carcinophaga and 11 adult specimens of E. barbatus. We then performed an F test of equal variance on these two datasets in R. We found that crabeater seal tooth gaps are significantly less variable in spacing than those of bearded seals. This result supports our hypothesis that there is a strong stabilizing selection for lower variability in tooth spacing of L. carcinophaga. Our work demonstrates that differential feeding ecologies can significantly impact morphological variation in pinniped dentition.