Stelzer, C. (2006). “Competition Between

Christianson-Heiska, I; Wahteristo, P.; Kastilan, E.; Bergelin E.; Bylund, G.;

Isomaa, B. (2004). “Effects of the wood extractive betulinol and 17?-

oestradiol on reproduction in zebrafish, Danio rerio (Hamilton)

complications due to a bacterial infection.” Journal of fish diseases 27(5), pp.


In this study, the existence of certain chemicals in waterways on the spawning and general reproduction capabilities of zebrafish was examined. The hypothesis was, simply put, that the exposure of zebrafish to the chemical betulinol (which is extracted from wood) would cause detrimental effects to the various reproduction mechanisms of both male and female zebrafish. The primary focus of the research, however, was to determine the precise mechanisms by which such detrimental effects would actually occur.

The results of the study basically supported the hypothesis, but with some surprising and unsought for results that showed a very different mechanism at work than the basic hormonal and other physiological effects that were directly predicted and examined.

These changes did occur, with female zebrafish showing increased and more intense spawning activities (which actually depleted their ability to effectively reproduce), while male zerbafish showed morphological changes in their testes in response to the exposure. Bacterial infections, however, appeared to have the biggest effect on reproduction, and these infections came as a complete.

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