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Studies in the mineral metabolism of the Hawaiian crab, Podophthalmus vigil (Fab.) throughout the ecdysis cycle
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|Title:||Studies in the mineral metabolism of the Hawaiian crab, Podophthalmus vigil (Fab.) throughout the ecdysis cycle|
|Authors:||Sather, Bryant Thomas|
|Abstract:||The molt cycle of crustaceans has already been the subject of a great number of investigations. Apart from descriptions of morphological changes, the mineral metabolism has been studied to a certain extent, particularly changes in calcium and phosphorus content. But such changes have only been investigated at random periods in the molt cycle, and only in certain tissues and organs (glands), particularly also with respect to hormonal influences (eyestalk hormones, etc.) on them. No data are available on this metabolism during the entire molt cycle, nor is anything known apparently of the concentrations and distribution of these elements in the animal at the times of calcification and decalcification, periods of major importance in the cycle. Very little is also known of the effect of certain extrinsic factors on the frequency of ecdysis of crustaceans in nature. It was therefore thought worthwhile to try and fill this gap in our knowledge of the physiological processes which occur in the crustacean molt cycle. Calcification and hard tissue formation occurs in many forms of life. It is found in algae (e.g., Porolithon, Halamita), in protozoans (Spirostomum), coelenterates, echinoderms, molluscs, arthropods and vertebrates. Generally, the purpose of calcification is to give form, support, and protection, but in certain instances it is considered to be a pathological condition. The calcium complex involved may be in three forms: calcite, aragonite, or apatite. The latter is a calcium phosphate compound, Ca10(PO4)6(OH)2, and the other two are calcium carbonate complexes. Very little phosphorus is found in calcite and aragonite, which are restricted to the lower phyla. The amount of strontium and magnesium present in the calcium carbonate complex determines the difference between aragonite and calcite. The latter has very little of these elements present in its crystal structure. Apatite is found in vertebrate bone, dentine, cementum and enamel. Regardless of the crystal structure and the phylogenetic group, the process of calcification is basically the same, although the purpose may be specifically adapted for different requirements. Two of the questions under investigation by many people are: (1) what controls the calcification process, and (2) what is the distribution pattern of the involved elements during the process? The process of how bone is formed in mammals is well known, but the controlling factors are much less well understood. The causes of calcification are the least known. Although the importance of calcium and phosphorus in the calcification processes, both in vertebrates and in invertebrates, has been recognized, that of certain other mineral elements, i.e., heavy metals, is very poorly understood, probably because they appear as so-called trace elements. Many are transitional elements and it is known that such may induce the greatest biological activity. Their study may reveal a definite effect on certain biochemical and physiological processes. Of such elements chromium is one of which very little is indeed known with respect to its role in mineral metabolism. Only two reports have appeared concerning the tissue fractionation and the effect of environmental factors on the uptake of radiochromium. In the Rainbow Trout, Knoll and Fromm (1960) studied the accumulation and elimination of hexavalent chromium. Townsley (1962) investigated the accumulation and loss of trivalent Cr51 in three invertebrates: the sipunculids, Physcosoma pelma and Aspidosiphon sp., and the brachiopod, Lingula reevii. In neither of the studies were the effects of: (1) different ionic species of chromium on the uptake, (2) metabolic inhibitors on the accumulation, and (3) metal discrimination against another element, followed. Its absorption and metabolism in crustaceans has never been reported either. Furthermore it is known that in mammals during calciphylaxis, the condition of induced hypersensitivity in which tissues respond to challenging agents with local calcification, chromium is one of the elements which directs calcium to certain tissues. Therefore it may be possible that chromium has some significance in the calcification processes of crustaceans. The study of the chromium metabolism during the molt cycle may even suggest similarities in the processes of calcification in crustaceans and those occurring in ossification in vertebrates.|
Thesis (Ph. D.)--University of Hawaii, 1965.
Bibliography: leaves 138-147.
vii, 147 l mounted illus., tables
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Ph.D. - Zoology|
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