Response of juvenile centrarchids to sublethal concentrations of waterborne selenium. I. Uptake,tissue distribution,and retention

Juvenile bluegill (Lepomis macrochirus and largemouth bass (Micropterus salmoides) contained significantly elevated levels of selenium in all tissues examined after exposure to 10 μ/l for 120 days. The relative accumulation of selenium in specific tissues was: spleen > heart > liver > kidney > erythrocytes > gill > plasma > white muscle > gonad > intestine > stomach > brain. Water temperature and hardness did not affect the equilibrium concentrations or tissue distribution observed after 90 days, although earlier values were influenced. Selenium concentrations remained unchanged after 30-day elimination trials in spleen, liver, kidney, and white muscle, but exhibited a half-life retention time ≤ 15 days in gill and erythrocytes. The largest difference between species was in the selenium content of white muscle, with bluegill concentrating approximately twice that of largemouth bass. The major uptake pathway appears to be crythrocyte transport mediated by active oxo-groups on the selenium anion, with subsequent exchange at preferential sites. High apportionment into the spleen and heart may be influenced by differential formation of selenoproteins. Even though no mortality resulted under these controlled experimental conditions, possible pathologic enhancement, combined with the added body burden from dietary intake, strongly suggest the potential for toxicity in natural systems where waterborne selenium concentrations approach 10 μ/l.