S3-2.1 Jan. 4 Living in cold. Temperature compensation in pteropod mollusk, Clione antarctica. DYMOWSKA, A.K.*; SEIBEL, B.A.; University of Rhode Island; University of Rhode Island email@example.com
In polar animals living at low temperatures, such as those experienced by C.antarctica, locomotory performance is constrained by slower generation of ATP1. Cold adaptation and acclimatization in ectotherms may result in increases in mitochondrial densities2, surface density of cristae, and enzyme concentrations3, presumably to increase aerobic capacity. All of the above were investigated in locomotory muscles of C.antarctica (habitat temperature -1.8ºC) and its temperate sister species C.limacina (habitat temperature 10ºC). Even though mitochondria occupied ~ 0.35 volume of slow-twitch muscle fiber in both species, changes in the relative proportion of fast- and slow-twitch muscle fibers made the volumes per muscle bundle much greater in C. antarctica (0.365±0.016) than in the temperate C.limacina (0.197±0.018). In fact, fast-twitch muscle was completely displaced in Antarctic congener. Differences were also observed in the mitochondrial ultrastructure. C. antarctica had approximately 1.7-times higher cristae surface density (58.157±1.351µm2/µm3) than C. limacina (34.272±0.826µm2/µm3). Further, in Antarctic species citrate synthase activity was twice as great in whole organism (2.965±0.169 unit g-1 compared to 1.408±0.141 unit g-1) and almost four-times higher in the isolated locomotory muscles. These results indicate higher aerobic capacity in C.antarctica that enables it to swim routinely in polar waters of Southern Ocean at comparable rates as C.limacina in temperate waters of Northern Atlantic4. However, burst capacity is completely lost in C. antarctica, which relies instead on whole-body withdrawal and chemical defense for predator avoidance4. 1. Clark. 1983. Oceanogr. Mar. Biol., Annu. Rev. 21,341-453. 2. Johnston et al. 1998. J. Exp. Biol. 201, 1-12. 3. Crockett and Sidell. 1990. Physiol. Zool. 63, 172-288. 4. Borrell et al. 2005. J. Exp. Biol. 208, 2939-2949.