4-nonylphenol-induced toxicity and apoptosis in Hydra attenuata.

Effects of 4-nonylphenol (4-NP) on the morphology and survival of the cnidarian Hydra attenuata were studied under acute exposure conditions. The lethal concentration value inducing 50% mortality after 96 h was 97.5 +/- 20 microg/L, whereas the lethal concentration value inducing 10% mortality after 96 h was 64 +/- 25.5 microg/L. The no-observed-effect concentration based on morphological criteria was less than 25 microg/L. Hydra was one of the most sensitive freshwater invertebrate species behind the amphipod Hyalella azteca. Toxicity effects appeared rapidly and did not evolve substantially between 24 and 96 h of exposure. Induction of apoptosis was registered during the first hour of exposure to 4-NP at lethal concentrations, indicating rapid effects of the chemical. Abnormal increase of apoptosis may explain the acute toxicity of 4-NP in hydra. Results show that hydra viability is affected in the short term at 4-NP concentrations normally found in contaminated sites, but not at those concentrations reflecting lower levels of environmental contamination.