Copper uptake and excretion by Busycon canaliculatum L.

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Pathways of copper into Busycon canaliculatum and sites of accumulation were investigated in uptake experiments using 64Cu. Routes of possible copper loss were investigated in excretion experiments and by determination of copper content of egg capsules. Uptake of dissolved 64Cu by 38 whelks followed a smooth curve, slowing with time; about 2/3 of the available 64Cu in 3 l of water was absorbed by 48 hr. The rate of uptake was proportional to the concentration of the medium. Among the soft tissues, 64Cu appeared first on the gills, which in 1 hr reached a normalized concentration 100 times that initially present in the medium, and in the blood and kidney (normalized concentration = 1 at 1 hr). By 6 hr of exposure, 64Cu appeared in the gut and digestive gland (normalized concentration = 5). The 64Cu continued to accumulate in the digestive gland, so that by 48 hr, this tissue contained 50% of the total copper taken up by the gill and organs of the visceral mass. Transfer of absorbed copper to the digestive gland continued even when whelks were removed to unlabeled sea water for 24 hr. Separations carried out on blood from whelks labeled with 64Cu indicated that the absorbed copper in the blood was nonspecifically bound to hemocyanin. Excretion rates for copper averaged 7 μg/24 hr per 100 g fresh tissue weight, and appeared unaffected by the copper concentration of the medium. Under normal environmental copper concentrations, rates of dissolved copper uptake and of copper excretion are probably about equal. The average copper content of egg capsules was 23 μg/capsule. Spawning may be a significant route for copper loss, and an increase in copper excretion in autumn is also suggested as an explanation for a drop in tissue copper concentrations at this season.

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