Selenium-induced mortality and tissue distribution studies in Tenebrio molitor (Coleoptera: Tenebrionidae)

Results are reported on the survival patterns of newly emerged Tenebrio molitor L. reared in nutrient media supplemented with 0.125, 0.25, or 0.5% sodium selenite. One group was transferred to sodium selenite-containing medium after 1 wk in control medium, and another group was transferred after 1 wk from sodium selenite medium to control ration. Survival percentages and slope of survival curves are compared with control values. Results demonstrate a pronounced toxic effect of selenium which appears to be residual in those beetles transferred from the medium-containing selenium. Other T. molitor were reared in sodium selenite-containing media and, on days 3, 7, and 11, beetles were killed and the selenium content (ppm/mg tissue) of Malpighian tubules, digestive tract, and reproductive tracts were determined using fluorometric analysis. Results are reported correlating selenium content in the different organs to time of exposure to selenium and to concentration of sodium selenite in the incubation media. Malpighian tubules appeared to accumulate the greatest amount of selenium, the digestive tract was second, and the reproductive tissues accumulated the least amount of selenium. There appeared to be a direct dose accumulation relationship for Malpighian tubules but not for digestive or reproductive tissues; at the 0.25 and 0.5% treatments, no statistically significant differences were noted in the amounts of selenium that were present.