gene expression

The number of chemical products produced by men is enormous. At present the number of chemicals registered by the Chemical Abstract Service exceeds 20 million. Estimations are that over 100.000 compounds are released in the environment in such volumes that they generate a potential threat for men and environment. Only little is known on the toxicological properties of this large group of chemicals. The scarce information available until now consists mainly of acute toxicity data. Long term adverse effects on populations, communities and ecosystems are poorly documented. The lack of chronic and long term data is illustrated by the phenomenon of endocrine disruption. Various chemicals are capable of interfering with the endocrine metabolism of several animal species leading to negative effects on their reproduction. There is a great deal of uncertainty about the possible adverse (endocrine disrupting) character of chemicals for men and environment due to the scarce availability of chronic toxicity data and restricted knowledge on the toxicological working mechanisms. Especially for the ecologically important group of invertebrates no clear assays for mechanistic evaluation of endocrinological pathways disruption are developed yet. It is clear that there is an urgent need for this kind of assays to provide both chronic relevant as well as mechanistic detailed data.

Although cadmium toxicity is a well studied theme in the field of aquatic toxicology, still little is known concerning the molecular mechanisms of its toxic action. Moreover most laboratory studies only consider waterborne cadmium exposure, whereas dietary exposure can also contribute to the accumulation and effects of cadmium in fish. For a better understanding of the toxic responses leading to adverse effects there is an increasing need for more sensitive tools to determine early reactions on cadmium exposure and accumulation.

In collaboration with the Molecular Laboratory of the Royal Institute of Natural Sciences.

In Flanders (Belgium), many fish species are declining at an alarming rate, several species have gone extinct in the last few decades, and many more risk the same fate. Water pollution and river management practices have reduced and extensively altered aquatic habitats. For many species, the number of populations as well as the number of individuals per population have decreased dramatically. Moreover, it seems very difficult for individuals to develop genetic adaptations to their polluted habitats, since adaptation through natural selection is a relatively slow process. Surprisingly, previous studies reveal that various species are capable of developing adaptations to changing environments at fast rates. Studying the occurence of genetic adaptations in natural fish populations inhabiting polluted streams can therefore be of great value to evaluate the consequences of human activities on aquatic ecosystems. This is of vital importance for setting up conservation strategies.