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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - FISHODOR (Integrating conspecific odors into tilapia reproductive behaviour)

Teaser

Summary

Chemical communication is the most ancient and widespread form of exchanging information; it is used by everything from bacteria to mammals. When a chemical message triggers a specific effect in the receiver, the substance is said to be a pheromone. The sensing of chemical signals, mainly via the sense of smell, plays an important role in social functioning, because olfactory information projects to brain regions (i.e. olfactory bulbs, OB; Telencephalon, Te) that are critical for mating, reproductive and cognitive levels. So, olfaction can provide a natural window to the brain, and an opportunity to examine neuronal mechanisms and brain function in a non-invasive way. Nowadays Mozambique tilapia is highly valuable culture fish in many parts of the world from Asia and South America to Europe, because there is an economic specie in aquaculture and easily to rear in captivity (i.e. quite adaptable to a wide range of environments of salinity and temperature), and reproductively active all the year round. However, escapees suppose a higher environmental risk because they may become pets competing with autochthonous species. Mozambique tilapia released pheromones via urine to signal social position, and attract and stimulate females to spawn. Therefore, our overall aim is to provide novel information on the mechanism of action of pheromones, and elucidate the components of neuronal network from the olfactory system to the central nervous system. In this regard, we demonstrated that 0.1mM CuSO4 is the sub-lethal concentration can impair the olfactory detection of sex pheromone and reproduction process, but not affect to welfare condition of animals. These results will also be relevant at ecological and toxicological level because will be useful to establish a range concentration of heavy metal to reduce devastating impact and control population during intensive culture of tilapia, as well as reducing the deterioration and contamination of surface water and riverine sediments to result in a loss of biodiversity at environmental level.Moreover, our results make important contributions to the aquaculture of this novel food resource through the development of new tools to population control necessaries to reduce its devastating impact at ecological level, as well as promoting the future aquaculture of tilapia as healthy and novel food resource at global level.

Work performed

The project will originate novel and important contributions to fish neurobiology. The research will be carried out by a multidisciplinary team, employing several techniques from fields such as electrophysiology, molecular biology, transcriptomics and bioinformatics, to tackle a significant biological problem. It thus constitutes excellent training for the research fellow in order to become an independent scientist. First, it will provide important specific information in the olfactory transduction pathways and the olfactory neurones involved in the chemical reception of a pheromone in tilapia. Secondly and perhaps most importantly, it will be the first deorphanisation of a confirmed pheromone receptor in a fish species. It will also be an important step for understanding the mechanisms of pheromone signal integration and a basis to assess the evolutionary importance of chemical signaling in cichlid speciation.

Final results

Our results have important impact on ecological and toxicity studies. We demonstrated the sub-lethal concentration of heavy metals (i.e. cooper, Cu) and time exposures that can impair the olfactory detection of sex pheromone and reproduction process, but not affect to welfare condition of animals. Moreover, ciliated cells will be the main olfactory neuron cells that located mostly of olfactory receptors, and cAMP will be the main intracellular pathway of these olfactory receptors. At transcriptomic level, we found 30 olfactory receptors genes that will be good candidate to bind with sex pheromones in male Mozambique tilapia because they are downregulated by copper which evoke the main inhibitory effect of olfactory activity for either isoforms sex-pheromones. Although sub-lethal copper concentration (i.e. 0.1mM) not affect to welfare condition after 9 days of treatment, we found that this metal exposure have a physiology and neuroendocrine cost during the reproductive process. In this sense, copper significantly decrease on the expression of key genes of neuroestrogens system (i.e. brain aromatase-cyp19b, androgen receptors-ar and estrogen receptor-er) and can evoke aromatization effect (i.e. conversation of testosterone in estradiol), as well as changes in social-sexual behaviour (i.e. reduce aggressive behaviour). Furthermore, cooper decrease the mRNA levels of gonatropin system genes (i.e. gnrh and gth) and have negative consequences at hormonal (i.e. 11-Kt) and gonadal (i.e. GSI) level, without significance consequences on growth and welfare in male tilapia. So, we can establish that 0.1mM CuSO4 is the sub-lethal concentration required to population control of Mozambique tilapia reared in captivity. These findings would not therefore only be important for academia, but also ultimately for aquaculture practice, and may reinforce therefore the already strong European competitiveness in the area of new and healthy resource food and environmental management.