Abstract
Calcium (Ca+2) was histochemically localized in antennal glands during the molting cycle of the crayfish Procambarus clarkii. In tissues involved in electrolyte reabsorption, alizarin red S formed precipitates with Ca+2 (4-30 iim in diameter). In the coelomosac, the number of Ca+2-alizarin precipitates did not vary significantly during the molting cycle. In labyrinth and nephridial canal tissues, Ca+2 precipitates were significantly more abundant during postmolt than during intermolt, with a maximum at 4 days postmolt; by 14 days postmolt, Ca+2 precipitation had decreased in the labyrinth and nephridial canal, although t he values remained significantly greater than intermolt levels. Distal nephridial canal cells treated with potassium oxalate contained mitochondria with electron-dense precipitates (30-85 nm in diameter). These deposits reached a maximum at 4 days postmolt, but remained significantly above intermolt levels by 14 days postmolt. These findings suggest that Ca+2 accumulates in reabsorptive tissues during postmolt and that the mitochondria of distal nephridial canal cells may also serve to maintain intracellular and extracellular Ca+2 homeostasis. Additional key words: nephridial canal, labyrinth, alizarin red S, K+-oxalate, histochemistry The molting cycle of a freshwater crayfish can be used as a model system to study cellular mechanisms of calcium transport associated with cuticular calcification and decalcification. At intervals, the old cuticle is decalcified, and a new cuticle is formed underneath. Once the old cuticle is shed at ecdysis, the new cuticle undergoes calcification. During the molting cycle, these animals experience physiological challenges related to ionic regulation that are more pronounced in freshwater than in saltwater, specifically, low calcium
Published Version
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