Research to find out the impact of glyphosate on trout | Handles

2022-11-22 08:13:18

The “Virology, immunology and ecotoxicology of fish” unit (VIMEP) of the Ploufragan-Plouzané-Niort laboratory of Anses has carried out several experiments on rainbow trout to evaluate the effect on their health of pure glyphosate and two commercial herbicides containing it.

The study was carried out as part of the GlyphoTAC project, which was the subject of a university thesis supported by Jessy Le Du-Carré. This work was funded by the Brittany region, the Côtes d’Armor departmental council and the Saint-Brieuc urban community. Few studies of this type, carried out on several generations of aquatic animals, have been carried out to date, due to their complexity of implementation.

« We studied the exposure of rainbow trout over several generations: the effect on the directly exposed fish but also on the following two generations, themselves exposed or not.explains Morgane Danion, scientist in the unit and co-supervisor of the thesis. Trout is a good model for ecotoxicology studies because we know its biological functioning well and it is sensitive to the quality of its environment. »

Various effects that can affect the health or survival of fish

The exposures were carried out over a long time, at concentrations comparable to those measured in a natural environment. No increase in mortality directly due to exposure to the active ingredient (glyphosate) or the two products tested containing it was observed, nor any negative effect on reproduction. On the other hand, the behavior and several biological parameters of the exposed fish were modified.

In particular, it was highlighted a reduction in the ability to react to changes in light in larvae from parents and/or grandparents exposed to pure glyphosate or herbicides. This might translate in nature into less reactivity to escape predators.

Another experiment showed a reduction in the diversity of microorganisms present on the gills fish following exposure to pure glyphosate and herbicides. However, it is a key organ for exchanges with the external environment and maintaining animals in good health.

Consequences on the offspring of exposed fish and effects that differ between pure glyphosate and herbicides

This research also shows that the most significant effects do not occur in the first generation of exposed fish, but mainly in fish descendants of exposed parents and/or grandparents. In addition, differences in effects between the active substance alone and the more complex commercial products are observed. According to the conditions of the different experiments carried out, we see that product formulation increases or reduces the effect of glyphosateor even causes an effect not observed in trout exposed to the pure active substance.

For example, if no change in survival from an experimental viral infection was observed in the first generation of fish, mortality due to viral infection in trout whose parents were exposed to herbicides was modified, increase or decrease depending on the product tested, compared to the control group. However, it was not affected in fish exposed to pure glyphosate or in their descendants.

Impacts have also been observed on the expression of enzymes involved in energy metabolism, the quantity and/or efficiency of certain immune cells or even developmental disturbances (malformations), particularly in larval stages.

Questions regarding the mechanisms at the origin of these effects

Additional studies are needed to try to understand the mechanisms behind these observations, and in particular how the effect of toxicity is transmitted from one generation to the next. “ The two commercial products tested were withdrawn from the market in 2018 and 2019. This decision is independent of the results of our studies. We can nevertheless imagine that there might be comparable effects for other products based on glyphosate or other active substances still on the market. It seems particularly relevant to us to continue working on long exposures to environmental doses, by carrying out studies over several generations. », concludes Thierry Morin, head of the VIMEP unit.

Better knowledge of the toxicological mechanisms at the origin of these observations would make it possible to consider taking these effects into account in the evaluation of active substances or products, prior to their authorization.

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