Oestrogenic Activity of Tropical Fish Food Can Alter Baseline Vitellogenin Levels in Male Fathead Minnow (Pimephales promelas)

Vitellogenin (VTG) is a precursor of egg-yolk protein and is therefore present at high concentrations in the plasma of female fish. In male fish, VTG concentrations are usually undetectable or low, but can be induced upon exposure to oestrogenic substances either via the water or the diet. This work was carried out to determine the reason for apparently elevated VTG concentrations in unexposed stock male fathead minnow maintained in our laboratory. The results showed clearly that some of the food given to the fish was oestrogenic and that replacement of this with non-oestrogenic food led to a significant reduction in the basal VTG levels measured in male fish after a 6 month period. This reduction in male VTG concentrations drastically increased the sensitivity of the VTG test in further studies carried out with these fish. Moreover, a review of published concentrations of VTG in unexposed male fathead minnow suggests that this problem may exist in other laboratories. The fathead minnow is a standard ecotoxicological fish test species and so these findings will be of interest to any laboratory carrying out fish tests on endocrine disrupting chemicals. Keywords–Vitellogenin, Fathead minnow, Fish diet, Oestrogenic food