Respiratory constraints on dive times in baleen whale calves
Authors:
Jennifer Rodriguez, Kassondra Stanwood, Areli Tejeda, Alexis ZumbrunnMentor:
Rachel Cartwright, Biology Lecturer, California State University Channel IslandsMarine mammals require a wide range of adaptations to support their aquatic lifestyle, not least as air-breathers, they require the ability to breath-hold and tolerate apnea when they dive. Previous studies have shown that the aerobic capacity of odontocetes (toothed whales) increases with age, but despite the importance of these attributes, no such study has focused on mysticetes (baleen whales). Myoglobin, a protein found in muscle tissue, acts as an intracellular oxygen storage site within muscle cells. In marine mammals it is used to deal with their apnea when they are diving. In odontocete calves low levels of myoglobin constrain their ability to tolerate apnea and limit their breath-holding capacity. In this study we used tissues obtained from a range of stranded mysticete calves (humpback, gray and minke) to test our hypothesis that mysticete calves also have lower levels of myoglobin compared to adults. Our results showed that this was true. Our data showed that for myoglobin the difference was significant (Mean Mb levels for calves = 0.316 grams/ 100 grams fresh tissue s.d.= 0.070, mean for adults= 1.888 g/100gft s.d.=0.927: t= -4.474, d.f. =6.081, p = 0.004) We also compared buffering capacity in calf vs. adult baleen whales. In marine mammals, buffering capacity reflects their ability to deal with the lactic acid byproduct produced when they are forced to use anaerobic respiration while diving. Our results showed little variation between calf and adult baleen whales (Mean buffering capacity for calves = 45.80 slykes s.d.= 14.98 mean for adults= 38.65 slykes s.d.= 0.919: t= 0.640, d.f.=6 p = 0.546). Understanding the constraints on marine mammals when diving is important because it affects their ability to forage effectively and swim efficiently in the marine environment.