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 mu m 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 postmo by 14 days postmolt, Ca+2 precipitation had decreased in the labyrinth and nephridial canal, although the 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. [References: 27]
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