Effects of 4-n-nonylphenol and 17beta-oestradiol on early development of the barnacle Elminius modestus. 
Pollutants that are present in the aquatic environment and cause abnormal endocrine function in wildlife populations have been termed endocrine disrupting chemicals (EDCs).  The impacts of these chemicals on the reproduction and development of vertebrates has been shown to be significant in both field studies and laboratory experiments.  Over the past decade the number of investigations into the impacts of EDCs that affect reproductive and sexual characteristics (reproductive EDCs) has increased and evidence of their potency is evident in numerous wildlife species and through data from in vitro tests.  However, little information is available on whether chemicals which act as EDCs in vertebrate species affect aquatic invertebrates.  The case of imposex in archeogastropods following exposure to tributyltin (TBT) is a notable exception.  Moreover, a number of studies have shown that development, fecundity and reproductive output of some aquatic invertebrates are affected significantly by exposure to pollutants.  In order to determine whether external signs of exposure to vertebrate EDCs can be observed and monitored in invertebrate species, we exposed larvae of the barnacle Elminius modestus to environmentally realistic concentrations of the xeno-oestrogen, 4-n-nonylphenol (NP), and the natural oestrogen, 17beta-oestradiol (E(2)).  Early life stages (nauplii and cyprids) were also exposed in the laboratory to determine whether there were effects on the timing of larval development and settlement.  Ovary development and size of juveniles was measured following chronic exposure.  Exposure to NP in the concentration range 0.01-10 µg l(-1) resulted in disruption of the timing of larval development.  Similar results were obtained with E(2).  Pulse exposures showed that the timing of exposure is critical and exposures for a period of 12 months caused long-term effects.  A linear, concentration-dependent response was not evident.