Meeting Abstract

P2-190  Saturday, Jan. 5 15:30 - 17:30  Hybrid fibers in the bearded seal longissimus dorsi muscle BALLARD, E.J.**; BARRETT, L.M.; DEAROLF, J.L.; THOMETZ, N.M.; BRYAN, A.; REICHMUTH, C.; Hendrix College, Conway, AR; Univ. of San Francisco, CA; Alaska Dept. of Fish and Game, Fairbanks; Univ. of California, Santa Cruz

Bearded seals (Erignathus barbatus) are shallow diving pinnipeds that mostly stay in depths of about 100 meters or less. Being benthic feeders, they scour the ocean floor searching for food sources like polar cod, sculpins, shrimp, spider crabs, and a variety of other invertebrate species. Their benthic habits are a unique aspect of the life of bearded seals in the Arctic, which makes their diving ability an interesting topic of study. Specifically, understanding the physiology of bearded seal locomotor muscle could provide key insights into these abilities. Thus, the goal of this study was to quantify the percentages of hybrid fibers, fibers expressing more than one myosin heavy chain, in the longissimus dorsi (LD) of bearded seals. To achieve this goal, samples of bearded seal LDs were stained for their myosin ATPase activity after alkaline pre-incubation and their reaction to two myosin heavy chain antibodies: SC-71 (type IIA - fast-twitch oxidative-glycolytic), and A4.951(type 1 - slow twitch). Then, images were taken from identical regions in each of these samples using a Zeiss Axio Imager AI microscope and AxioVision v. 4.7 software. On the images, we identified slow- and fast-twitch fibers that were staining for both A4.951 and SC-71 and determined the percentages of these fibers in the LDs of the seals. Using ImageJ, we also measured the diameters of both types of hybrid fibers. From these data, we calculated overall averages of the percentages and diameters of the slow and fast-twitch hybrid fibers. Studying the hybrid fibers in the LDs of bearded seals will give us valuable insight into the unique diving abilities of the bearded seal.