Ingestion of Colloidal Material and Water by Goldfishi

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Abstract
Goldfish engulf dyes in soln. and in suspension, and minute C particles, including finely ground charcoal, and India ink are also accumulated in the intestine. Others have, reported similar experience for fresh-water fishes. Colloidal Th dioxide ("thorotrast") with a mean particle size of 7 and a range of from 3 to 10 millimicrons is accumulated in the intestine, frequently in large quantities, as shown by X-rays. No trace of thorotrast was found in the mouth. Only one of the several dyes tested (methylene blue) produced observable coloration in the oral region, and that one gave only a faint trace of color. Th dioxide can be detected in the intestine after the fish spend as little as 1 hr. or as much as 96 hrs. in the colloidal suspension. These are the shortest and longest exposures tested. The concns. used ranged between 0.7 and 4% thorotrast, with the majority containing 1.3%. Thorotrast is engulfed with or without previous starvation and with or without the goldfish being handled before exposure. The observations give strong evidence that goldfish swallow water and the substances it contains; in short, that they drink fresh water.

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