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Chapter 9 The Anoxia-Tolerant Crucian Carp (Carassius Carassius L.)

2009; Academic Press; Linguagem: Inglês

10.1016/s1546-5098(08)00009-5

1557-8011

Matti Vornanen, Jonathan A. W. Stecyk, Göran Nilsson,

Adipose Tissue and Metabolism

The crucian carp is probably the most anoxia-tolerant fish there is, surviving without oxygen for days to months depending on temperature. The anoxia tolerance has evolved in response to over-wintering in ponds and small lakes that can become anoxic for months during the winter. The exceptional anoxia tolerance of the crucian carp is based on special physiological traits that are either constitutively expressed or seasonally primed. A key to its anoxia tolerance is its constitutive ability to produce ethanol as the major anaerobic end product. The ethanol production is supported by massive stores of glycogen in various tissues, and these stores are largest in the autumn before the onset of wintertime anoxia. Metabolic depression is less pronounced than in anoxia-tolerant turtles and there is no major down-regulation of membrane permeability in brain ("channel arrest"), possibly with the exception of reduced NMDA receptor function. Increased levels of the inhibitory neurotransmitter GABA and low levels of the excitatory transmitter glutamate together with a modest activation of glycolysis probably ensure energy balance to the anoxic brain and aid to maintain normal ion gradients across neuronal membranes. The heart has been found to sustain cardiac output in anoxia, possibly to allow for substrate transport and a sufficient rate of ethanol release to the water. Like the brain, the heart also shows few signs of reduced ion permeability in anoxia. However, a lack of compensatory temperature acclimatization suggests that it is utilizing the low winter temperature to suppress its energy needs during anoxia.