Presenter(s): Megan Pollak—Earth Sciences—Paleontology
Faculty Mentor(s): Kellum Tate-Jones
Session 6: The Earth, Sky & Everything In Between
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 (i .e ., Lobodon carcinophaga) is unique among pinnipeds as a filter-feeder . The distinct sieve-like postcanine tooth processes such as high-cuspation and intricate trellis-like morphology allow the crabeater seal to effectively strain small krill from the water . I hypothesize that individuals in this group with unevenly spaced teeth are unlikely to survive ecological pressures and are thus removed from the population by natural selection, leading to lesser variation in crabeater seal tooth spacing than in grab-and-gulp feeders . I test this hypothesis by assessing whether the distinctive feeding method of the crabeater seal constrains tooth spacing by comparing the variability in tooth gaps of crabeater seals to that of bearded seals (i .e ., Erignathus barbatus) . I measured the tooth gaps between the postcanine teeth of 21 specimens of L . carcinophaga and 11 specimens of E . barbatus . I then performed an F test of equal variance on these two datasets . I found that crabeater seal tooth gaps are significantly less variable in spacing than those of bearded seals . This result supports my hypothesis that natural selective processes have generated evolutionary constraints for lower variability in tooth spacing in the filter- feeder, L . carcinophaga, than in grab-and-gulp feeders such as E . barbatus .