Publication Abstract

A stickleback ring test in view of reducing the number of fish used in regulatory testing

G.S.E. Rimmer*, I. Barber, J.P. Sumpter, I. Katsiadaki*

The Fish Sexual Development Test (FSDT) is a test guideline under validation by the relevant task force of the Organisation for Economic Co-operation and Development (OECD). The test aims to identify compounds with endocrine modulating activity, widely called endocrine disruptors (EDCs). The main advantage of the stickleback over the other fish species participating in the validation exercise (the fathead minnow, Pimephales promelas, and the zebrafish, Danio rerio, is the availability of a genetic sex marker. The Japanese medaka (Oryzias latipes), another fish species with a genetic sex marker, has the same advantage as the stickleback but it also presents a drawback; the condition of intersex (the presence of both male and female gametes in a single gonad), which would be of diagnostic value under the FSDT, is commonly met in control fish. The main endpoint employed by the FSDT is sex ratio, which in the case of the stickleback can be assigned genetically using a simple PCR test. In the case of alternative models, sex is assigned by means of gonadal histology, a strategy that presents many drawbacks. Firstly, an acceptable sex ratio for the control groups does not need to be defined waiving the risk of test failure. Secondly, the mode of action of a chemical can be better defined because any differences between genetic and histological sex can be attributed to the chemical exposure. Thirdly, but most importantly the ability to assign genetic sex increases the power of the test and can dramatically reduce the number of animals used in scientific procedures for both research and regulatory purposes. If the stickleback ring test, funded by the NC3Rs proves robust, sensitive and reproducible, then the stickleback will be proposed as the species of choice for this test, resulting in a significant reduction in the numbers of fish used in research and regulatory testing. 

Reference

G.S.E. Rimmer*, I. Barber, J.P. Sumpter, I. Katsiadaki* (2009) A stickleback ring test in view of reducing the number of fish used in regulatory testing. 6th International Conference on Stickleback Behaviour and Evolution