Intersex in Scrobicularia plana: transcriptomic analysis reveals novel genes involved in endocrine disruption.

Intersex, the appearance of female characteristics in male gonads, has been identified in a wide range of aquatic species worldwide, yet the underpinning molecular etiology remains uncharacterized. The presence of intersex has been shown to be a widespread phenomenon in bivalve, S. plana, populations from the southwest coast of the U.K., as well as inducible in an experimental exposure regime using endocrine disrupting compounds (EDCs). Herein, we use the suppressive subtractive hybridization approach to isolate differentially expressed transcripts in S. plana males exhibiting intersex. Transcripts involved in cell signaling, cell cycle control, energy production/metabolism, microtubule assembly, and sperm physiology are all highlighted as differentially expressed in intersex male clams. These provide both an insight into the molecular mechanisms of action involved in the development of intersex, as well as facilitating potential molecular-level "early warning" biomarkers of the condition.

Demonstration of a consensus approach for the calculation of physicochemical properties required for environmental fate assessments.

Eight software applications are compared for their performance in estimating the octanol-water partition coefficient (Kow), melting point, vapor pressure and water solubility for a dataset of polychlorinated biphenyls, polybrominated diphenyl ethers, polychlorinated dibenzodioxins, and polycyclic aromatic hydrocarbons. The predicted property values are compared against a curated dataset of measured property values compiled from the scientific literature with careful consideration given to the analytical methods used for property measurements of these hydrophobic chemicals. The variability in the predicted values from different calculators generally increases for higher values of Kow and melting point and for lower values of water solubility and vapor pressure. For each property, no individual calculator outperforms the others for all four of the chemical classes included in the analysis. Because calculator performance varies based on chemical class and property value, the geometric mean and the median of the calculated values from multiple calculators that use different estimation algorithms are recommended as more reliable estimates of the property value than the value from any single calculator.

Widespread contamination of coastal sediments in the Transmanche Channel with anti-androgenic compounds.

This study analysed the levels of androgen receptor antagonist activity in extracts of coastal sediments sampled from estuaries in southern UK and northern France. Anti-androgenic (AA) activity varied between <0.2 and 224.3±38.4µg flutamide equivalents/g dry weight of sediment and was significantly correlated with the total organic carbon and silt content of samples. AA activity was detected in tissues extracts of clams, Scrobicularia plana, sampled from a contaminated estuary, some of which was due to uptake of a series of 4 or 5 ring polycyclic aromatic hydrocarbons (PAHs). Initial studies also indicated that fractionated extracts of male, but not female, clams also contained androgen receptor agonist activity due to the presence of dihydrotestosterone in tissues. This study reveals widespread contamination of coastal sediments of the Transmanche region with anti-androgenic compounds and these contaminants should be investigated for their potential to disrupt sexual differentiation in aquatic organisms.

Intersex related gene expression profiles in clams Scrobicularia plana: Molecular markers and environmental application.

Intersex, the appearance of female characteristics in male gonads, has been identified in several aquatic species. It is a widespread phenomenon in populations of the bivalve, Scrobicularia plana, from the southwest coast of the U.K. Genes previously identified as differentially expressed (ferritin, testicular haploid expressed gene, THEG, proliferating cell nuclear antigen, PCNA; receptor activated protein kinase C, RACK; cytochrome B, CYB; and cytochrome c oxidase 1, COX1) in intersex clams relative to normal male clams, were selected for characterisation and an environmental survey of the Channel region. Transcripts were significantly differentially expressed at sites with varying intersex incidence and contaminant burdens. Significant correlations between specific gene expressions, key contaminants and sampling locations have been identified, though no single gene was associated with intersex incidence. The results highlight the difficulty in understanding the intersex phenomenon in molluscs where there is still a lack of knowledge on the control of normal reproduction.