Tissue respiration and seasonal acclimatization in the American oyster, Crassostrea Virginica (Gmelin)

Percy, J. A. (1968) Tissue respiration and seasonal acclimatization in the American oyster, Crassostrea Virginica (Gmelin). Masters thesis, Memorial University of Newfoundland.

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Abstract

The respiration rates of excised gill, mantle and adductor muscle of the American Oyster, Crassostrea virginica were measured by the Warburg technique, under various conditions of temperature and salinity and at various times during the summer and autumn. -- The relative rates of the tissues, when compared to gill respiration as a base, are similar to those reported for a number of other bivalves. -- The respiration rate of the mantle is inversely proportional to the Butler "condition" index of the oyster. This is attributed to glycogen accumulation. No significant correlation between "condition" index and either gill or adductor, muscle respiration was apparent, a probable consequence of the low, more stable glycogen content of these tissues. -- Dilution of the sea water medium to 13⁰/₀₀ results in stimulation of gill respiration, has no significant effect on mantle respiration, and severely inhibits adductor muscle respiration. -- Rate - temperature curves over the range 12°C - 40°C are presented for all three tissues. The maximum Q₁₀ coefficients for gill and mantle respiration and the minimum for adductor muscle respiration, occur in the 16°C - 20°C range. -- The respiration rates of gill and mantle, measured at 20°C in sea water of density 1.0250, declined by 16.8 percent and 18.4 percent, respectively, during late August - early September, indicating reverse acclimatization. The adductor muscle did not exhibit a corresponding decrease, and in fact its respiration rate may- have increased somewhat. -- It is concluded that the reverse acclimatization observed in gill, mantle and the intact animal is not attributable to a) seasonal fluctuations in "condition", because autumnal metabolic depression occurred over the whole "condition" range investigated, b) decreased ventilatory efficiency, because ventilation is not limiting under the experimental conditions or c) direct depressent action by the nervous system. The possible roles of intracellular changes and of nutritional and reproductive hormones, in the observed acclimatization effect are also discussed. -- The autumnal respiratory depression observed in the intact oyster can be partially accounted for by alterations in the metabolism of the major respiring tissues. -- A review of the occurrence of acclimatization in the Phylum Mollusca is presented.

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