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First published online August 9, 2007
Journal of Experimental Biology 210, 2866-2872 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.003749

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Relationship between food availability, glycerol and glycogen levels in low-temperature challenged rainbow smelt Osmerus mordax

William R. Driedzic^* and Connie E. Short

Ocean Sciences Centre, Memorial University of Newfoundland, St John's, Newfoundland, A1C 5S7, Canada

^* Author for correspondence (e-mail: wdriedzic{at}mun.ca)

Accepted 11 June 2007

Rainbow smelt Osmerus modax accumulate glycerol in winter that serves as an antifreeze. Fish were held at 8°C, or subjected to a decrease in water temperature to –1°C over a 19 day period, and subsequently maintained at –1°C from 15 January to 11 May 2004. Starved fish did not survive the challenge of temperature decrease, with death ensuing above the typical freeze point for marine teleosts (–0.8°C). A decrease in temperature activates the glycerol accumulation mechanism at about 5°C with peak plasma levels exceeding 300 µmol ml^–1. Glycerol levels begin to decrease in late February even at water temperatures below –1°C, suggesting either an inherent circannual or photoperiod trigger, possibly in association with sufficiently high levels of antifreeze protein. Glycogen levels in liver did not change significantly in starved fish maintained at 8°C. However, liver glycogen was depleted in fish subjected to the low-temperature challenge and at a faster rate in starved than in fed fish. Stored glycogen in liver and other tissues can account for only a small amount of the total glycerol production, suggesting a strong requirement for food during accelerated glycerol production. Liver glycogen levels increased in April and May in association with the decrease in glycerol. Levels of glycerol in liver, kidney, spleen, gill, intestine, heart, muscle and brain follow the same pattern as that in plasma. During the early part of the glycerol accumulation phase, all tissues except for liver have lower levels of glycerol in the intracellular space than the levels in plasma. In liver, glycerol is in equilibrium between the two compartments.

Key words: rainbow smelt, Osmerus mordax, glycerol, low temperature, freeze resistance

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This article has been cited by other articles:

				K. A. Clow, K. V. Ewart, and W. R. Driedzic Low temperature directly activates the initial glycerol antifreeze response in isolated rainbow smelt (Osmerus mordax) liver cells Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2008; 295(3): R961 - R970. [Abstract] [Full Text] [PDF]