THE IDENTIFICATION AND MEASUREMENT OF SUGARS IN THE BLOOD OF THREE SPECIES OF ATLANTIC CRABS

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Abstract
1. Blood glucose levels in the crab Cancer borealis ranged from 0.4 mg./100 ml. to 29.3 mg./100 ml. with a mean value of 8.6 mg./100 ml. In the same animals blood reducing substances were in the range 3.3-29.5 mg./100 ml. with a mean of 11.6 mg./100 ml. Blood glucose and reducing substances in the other two species of crabs tested, Cancer irroratus and Carcinas maenas, were in the same ranges.2. Changes in the blood glucose level account for most of the variations in reducing substances; the other components remain approximately constant, at about 3 mg./100 ml. The relationship between blood glucose and reducing substances is thus a simple straight line one.3. Variations of blood sugar levels during the molt cycle were found in Carcinas maenas and probably occur also in Cancer borealis. Qualitative changes in blood sugar composition also occur.4. Significant changes also occur in Cancer borealis females carrying eggs and at this time the relationship between blood glucose and reducing substances changes, the two values converging as the egg mass ages.5. Paper chromatography of the blood of these three species of crabs shows the presence of glucose, fructose, maltose, an unidentified reducing disaccharide and occasional traces of maltotriose and trehalose.

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