Body mass dependence of glycogen stores in the anoxia-tolerant crucian carp (<Emphasis Type="Italic">Carassius carassius</Emphasis> L.) |
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Authors: | Matti Vornanen Juha Asikainen Jaakko Haverinen |
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Institution: | (1) Department of Biology, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland |
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Abstract: | Glycogen is a vital energy substrate for anaerobic organisms, and the size of glycogen stores can be a limiting factor for
anoxia tolerance of animals. To this end, glycogen stores in 12 different tissues of the crucian carp (Carassius carassius L.), an anoxia-tolerant fish species, were examined. Glycogen content of different tissues was 2–10 times higher in winter
(0.68–18.20% of tissue wet weight) than in summer (0.12–4.23%). In scale, bone and brain glycogen stores were strongly dependent
on body mass (range between 0.6 and 785 g), small fish having significantly more glycogen than large fish (p < 0.05). In fin and skin, size dependence was evident in winter, but not in summer, while in other tissues (ventricle, atrium,
intestine, liver, muscle, and spleen), no size dependence was found. The liver was much bigger in small than large fish (p < 0.001), and there was a prominent enlargement of the liver in winter irrespective of fish size. As a consequence, the whole
body glycogen reserves, measured as a sum of glycogen from different tissues, varied from 6.1% of the body mass in the 1-g
fish to 2.0% in the 800-g fish. Since anaerobic metabolic rate scales down with body size, the whole body glycogen reserves
could provide energy for approximately 79 and 88 days of anoxia in small and large fish, respectively. There was, however,
a drastic difference in tissue distribution of glycogen between large and small fish: in the small fish, the liver was the
major glycogen store (68% of the stores), while in the large fish, the white myotomal muscle was the principal deposit of
glycogen (57%). Since muscle glycogen is considered to be unavailable for blood glucose regulation, its usefulness in anoxia
tolerance of the large crucian carp might be limited, although not excluded. Therefore, mobilization of muscle glycogen under
anoxia needs to be rigorously tested. |
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