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Tilapia now SA’s own bio-indicator of water pollution

Engela Duvenhage

Southern African water specialists can now use a local Tilapiine species – instead of alien fish species – to test whether water sources are polluted by compounds that can cause hormonal imbalances. Such chemicals can subtly mimic the female hormone oestrogen and alter the male hormone testosterone, whilst others disturb thyroid-hormone functioning.

Researcher Dr Marna Esterhuyse from the Botany and Zoology Department recommends the use of the hardy Mozambique tilapia – which is sensitive to water pollution – over that of the alien zebrafish which is currently often used as a bio-monitor.

“This work brings South Africa one step closer to its own fish model – similar to that of most developed countries – that can monitor chemicals in water sources that cause hormonal imbalances,” Dr Esterhuyse’s promoter, Prof Hannes van Wyk, believes. During such monitoring, scientists analyse the tissue, study the physiology and look at the changes in the genetic levels of fish species exposed to polluted water and chemicals.

“Aquatic animals are good bio-monitors because chemicals that cause endocrine imbalances are rapidly absorbed through the gills and stored in the body,” Dr Esterhuyse says.

Dr Esterhuyse’s toxicogenomic study focuses particularly on the interaction between pollutants and some of the genes specifically associated with the body’s endocrine systems. Due to Dr Esterhuyse’s genetic test model, fish exposed to a water sample can now be examined after only a few hours.

“Research on frogs, crocodiles and some fish species shows that endocrine disturbance caused by hormone mimicks in polluted water results in, inter alia, deviations in the reproductive system and in the malfunctioning of the thyroid gland,” Dr Esterhuyse explains.

Pesticides (such as DDT), household products, by-products of paper- and plastic manufacturing industries and contraceptives all contribute to the number of endocrine disrupting compounds in our water effluent.

Dr Esterhuyse is now extending these studies with postdoctoral work on genes influenced by thyroid hormones.

More information:

 Dr Esterhuyse mme2@sun.ac.za 

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