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(T/EH042) Intersexuality and sex reversal in the Three-spined Stickleback, Gasterosteus aculeatus - a bioassay for endocrine disrupting effects in fish. Hahlbeck, Edda1, Bengtsson, Bengt-Erik1, Griffith, Richard2, 1 2 ABSTRACT- Water from a variety of sources may contain substances of both natural and anthropogenic origin that interfere with the endocrine metabolism of aquatic animals. Many of these endocrine-disrupting chemicals resemble steroid hormones and have therefore the potential to adversely disturb sexual development in fish. Skewed sex ratios or intersex characteristics have been found in several fish species that have been exposed to municipal sewage and industrial effluents. Reproductive disturbances have been reported from Swedish inland and coastal waters as well as from other European regions. We have studied early sexual development of the three-spined stickleback, Gasterosteus aculeatus, to develop a bioassay for endocrine disrupting activity in fish. As a representative for temperate climate zones this small-sized teleost fish forms an alternative to tropic species that commonly are used in fish bioassays. It reproduces in the salinity range from sea to freshwater and can be studied at each stage of its life history, both under laboratory conditions and in the field. When we exposed juvenile sticklebacks for the natural estrogen estradiol and the synthetic estrogen ethinylestradiol, effects were visible after 5-6 weeks. The first two weeks after hatching seem to be the most sensitive time window for inducing intersexuality, i.e. the occurrence of oocytes in testicular tissue, or total sex reversal. Using a newly developed method for genetic sex identification (AFLP and PCR) we found that genetic males became feminised. The work is being extended by testing the androgen methyltestosterone. The findings from the laboratory experiments will be compared with field samples from different coastal regions of the Baltic Sea. Key words: stickleback, endocrine disruption, intersexuality, bioassay |
