Histological and histochemical studies of oocyte development in the bass, Dicentrarchus lubrux L., showed that three types of inclusions are formed during vitellogenesis. Lipid yolk accumulates first as lipid droplets, followed by protein yolk in the form of discrete protein yolk granules. The third type of inclusion are the small cortical alveoli (intravesicular yolk/yolk vesicles, i.e. ' carbohydrate yolk ')which form in the peripheral cytoplasm after both the lipid and protein yolk have started to accumulate. While the protein yolk granules maintain their structural integrity through to maturation, forming a densely packed zone in the mid-outer cortex, the lipid yolk droplets continually coalesce. and migrate centripetally, forming a prominent zone of large lipid droplets in the inner-mid cortex. From the histological study of oocyte development, a number of distinct developmental stages are delineated, while gross examination of the paired ovary revealed that, depending on its stage of development, it can be placed into one of seven maturity stages.

We report the development and validation of a novel in vivo biomarker test for waterborne androgens. During breeding, male sticklebacks (Gasterosteus aculeatus) manufacture a glue protein, spiggin, in their kidneys that they use to build their nests. Spiggin production is under the control of androgens. Until now, however, it has only been possible to quantify its production by measurement of the height of kidney epithelial cells. In the present study, we report the development of an enzyme-linked immunosorbent assay (ELISA) for spiggin and demonstrate its application to the measurement of spiggin in the kidneys of female sticklebacks that have been exposed to androgens in water. Results from the ELISA procedure revealed a strong correlation with measurement of kidney epithelial cell height (r2 = 0.93). However, the ELISA was much quicker and had a considerably higher response range (100,000-fold vs fourfold). Clear, graded responses in spiggin production were obtained by exposing intact females to increasing concentrations of 17a-methyltestosterone and 5alpha-dihydrotestosterone over three-week test periods. The lowest effective concentrations for these two steroids were 100 ng/L and 3 micorg/L, respectively. Female sticklebacks that were exposed to pulp mill effluent also produced spiggin in their kidneys. Possession of an androgen-regulated protein by the female stickleback makes it a unique bioassay organism for detecting androgenic contamination in the aquatic environment.

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Please cite this article as: Scholz, S., Mayer, I., Molecular biomarkers of endocrine disruption in small model fish, Molecular and Cellular Endocrinology (2007), doi:10.1016/j.mce.2008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. vertebrates. These endocrine disrupting chemicals (EDCs) are of high relevance for human 5 and wildlife health, since endocrine signalling controls many essential physiological 6 processes which impact on the individual's health, such as growth and development, stress 7 response, and ultimately reproduction and population development. Small fish represent a 8 cost-effective model for testing potential EDCs allowing the possibility to integrate from 9 molecular to phenotypic and functional effects. We have comprehensively reviewed 10 exposure-effect data from four different small model fish: zebrafish, medaka, fathead 11 minnow, and the three-spined stickleback. The majority of available data refer to EDCs 12 interfering with reproductive hormones. However, we have also included interactions with 13 other hormone systems, particularly the thyroid hormones. We demonstrate that the available 14 data clearly indicates the predictive potential of molecular biomarkers, supporting the 15 development and regulatory application of simple molecular-based screening assays using 16 small model fish for EDC testing.

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