Selenium (Se) is an essential element that can be harmful for wildlife. However, its toxicity in poikilothermic amniotes, including turtles, remains poorly investigated. The present study aims at identifying selenium toxicokinetics and toxicity in juvenile slider turtles (age: 7 months), Trachemys scripta, dietary exposed to selenium, as selenomethionine SeMet, for eight weeks. Nondestructive tissues (i.e. carapace, scutes, skin and blood) were further tested for their suitability to predict selenium levels in target tissues (i.e. kidney, liver and muscle) for conservation perspective. 130 juvenile yellow-bellied slider turtles were assigned in three groups of 42 individuals each (i.e. control, SeMet 1 and SeMet 2 ). These groups were subjected to a feeding trial including an eight-week supplementation period SP 8 and a following 4-week elimination period EP 4 . During the SP 8 , turtles fed on diet containing 1.1 ± 0.04, 22.1 ± 1.0 and 45.0 ± 2.0 lg g -1 of selenium (control, SeMet 1 and SeMet 2 , respectively). During the EP 4 , turtles fed on non-supplemented diet. At different time during the trial, six individuals per group were sacrificed and tissues collected (i.e. carapace, scutes, skin, blood, liver, kidney, muscle) for analyses. During the SP 8 (Fig. 1), both SeMet 1 and SeMet 2 turtles efficiently accumulated selenium from a SeMet dietary source. The more selenium was concentrated in the food, the more it was in the turtle body but the less it was removed from their tissues. Moreover, SeMet was found to be the more abundant selenium species in turtles' tissues. Body condition (i.e. growth in mass and size, feeding behaviour and activity) and survival of the SeMet 1 and SeMet 2 turtles seemed to be unaffected by the selenium exposure. There were clear evidences that reptilian species are differently affected by and sensitive to selenium exposure but the lack of any adverse effects was quite unexpected.
