The harp seal, Pagophilus groenlandicus (Erxleben, 1777). VII. A histophysiological study of certain skeletal muscles

• Published in: Canadian Journal of Zoology
• Main Authors: George, J. C., Vallyathan, N. V., Ronald, K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1971
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Harp Seal; Pagophilus groenlandicus
• Online Access: http://dx.doi.org/10.1139/z71-006; http://www.nrcresearchpress.com/doi/pdf/10.1139/z71-006

A quantitative and histochemical study of Ms. pectoralis, gluteus, psoas, diaphragma (dorsal, lateral, and ventral parts separately) of the harp seal was carried out. Myoglobin and iron contents of all the muscles were high, highest being of M. psoas. Fat and glycogen were low in all muscles. The low glycogen value was possibly due to rapid glycolysis during struggle in capture and while the animal was under an overdose of sodium pentobarbital that was administered for killing it. Phosphorylase and succinate dehydrogenase (SDH) activity levels were also low. Lipase (tributyrinase) activity was high, that of M. diaphragma being higher than the other muscles studied. The histochemical investigation revealed some of the morphological and biochemical properties of the component fibers. Two types of fiber, the red (type 1) and white (type 2), comparable to those of other skeletal muscles were distinguished in all muscles except in the case of M. pectoralis where an intermediate type was also seen in sections treated for the histochemical demonstration of SDH activity.The low levels of fat and SDH in the muscles indicate that fat is not a favored metabolite for muscular energy. The significance of the high lipase (tributyrinase) activity is doubtful. It is suggested that the role of this enzyme is to clear the fat so as to prevent the accumulation of fat in the muscles which are, by and large, geared for a glycolytic metabolism as an adaptation for the animal's diving habit. The high myoglobin content of the muscles, however, should provide the oxygen necessary for the oxidation of glucose during the initial part of the dive.