Abstract
The toxic effects of two commonly used glucocorticoids, the dexamethasone and prednisolone, on meiobenthic nematodes were assessed in a laboratory experiment for 30 days. Nine treatments were employed, comprised of two single and mixed concentrations of dexamethasone and prednisolone (i.e., 0.14 and 1.4 mu g center dot L-1). The exposure to both glucocorticoids showed significant effects on the abundance and taxonomic diversity of nematodes. Such changes were mainly induced by the decrease in the abundance of the species Microlaimus honestus, considered to be sensitive to prednisolone and by the increase in Enoplolaimus longicaudatus abundance, which can be considered tolerant. The exposure to these glucocorticoids also led to a decrease in 2A feeding groups, 2-4 mm body-size interval, and c-p3 life history type in most treatments, with type of life history and shape of amphids as the most relevant functional traits impacted by these two glucocorticoids. The results could also be explained by the potential antagonism between these two pharmaceuticals.