. A biology of Crustacea. Crustacea. BLOOD AND ITS CIRCULATION 43 The story of haemoglobin in Daphnia is made more complicated by the presence of an allied pigment in the gut. This is a haemo- chromogen called daphniarubin. Haemochromogens of various sorts can be made from haemoglobin by suitable chemical treat- ment, and it is reasonable to assume that the pigment in the gut of Daphnia is derived from its haemoglobin. But there is no simple relationship between haemoglobin in the blood and haemo- chromogen in the gut, so that we cannot be certain that Daphnia makes such a conversion, except i
. A biology of Crustacea. Crustacea. BLOOD AND ITS CIRCULATION 43 The story of haemoglobin in Daphnia is made more complicated by the presence of an allied pigment in the gut. This is a haemo- chromogen called daphniarubin. Haemochromogens of various sorts can be made from haemoglobin by suitable chemical treat- ment, and it is reasonable to assume that the pigment in the gut of Daphnia is derived from its haemoglobin. But there is no simple relationship between haemoglobin in the blood and haemo- chromogen in the gut, so that we cannot be certain that Daphnia makes such a conversion, except in one particular situation. We have already mentioned that Daphnia passes haemoglobin into its eggs; it has been noted that the concentration of haemoglobin decreases during embryonic development, and that once the gut of the embryo is formed haemochromogen begins to accumulate there in increasing amounts. In the embryos it would seem that haemo- globin is converted into haemochromogen. A summary of the changes involved in the synthesis and break- down of haemoglobin in Daphnia is given in fig. 25. Only one other crustacean with haemoglobin in the blood has been studied in detail comparable with the studies on Daphnia. This is the brine shrimp, Artemia salina. In this species the con- centration varies in much the same way as in Daphnia: there is more haemoglobin when oxygen is scarce. The amount of salt in the water where Artemia lives is often very high, and when this happens the oxygen content of the water is low, so that a false correlation appears between the salinity of the water and the haemo-. FIC2S Fig. 25. Diagram showing the main routes of transference during the synthesis and breakdown of haemoglobin in Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Green, J. (James), 1928-. Chicago, Q
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