It is possible to obtain mussels that do not accumulate toxins using genetic selection techniques. This is the conclusion reached after several years of study by researchers from various institutions, leading by Centro de Investigacións Mariñas (CIMA).
The aim of the Epitox project is determining if it is possible to produce certain mussel stocks that accumulate less toxins or, at least, at levels below those considered harmful from the sanitary point of view.
In the work, published in the magazine Aquaculture, it is shown that it is possible to do so, replacing or complementing wild seed with seed produced in a hatchery. This solution would contribute to solving the main mussel sector issue — toxins and red tides — and to obtain a product that is better adapted to consumers at a lower cost.
The Mediterranean mussel is one of the main species of European aquaculture and Galicia, with a production of around 200,000 tonnes per year, and it is the main producing region of Europe, occupying one of the first positions worldwide. But the main issue for mussel farming is the accumulation of toxins from microalgae blooms — commonly known as red tides — that are seriously threatening the farming activity of this and other marine bivalves in Galicia.
These recurrent toxic episodes, which have even increased in recent years, have determined the prohibition of mussel trading for long periods of time. Since this ecological event is a natural process, it is difficult to find a direct and definitive solution to this problem.
To try to reduce the impacts associated with these episodes, the Epitox project was launched, in which different research projects have been developed. One of them, coordinated by the Centre for Marine Research (CIMA) and in which the University of Santiago de Compostela (USC), Geneaqua, the Gulbenkian Institute of Science, the University of Gerona (UdG) and the Polytechnic University of Madrid, aimed to achieve, through selective breeding programs, strains of mussel with less toxin absorption and better detoxification or, ultimately, with a better balance between both processes.
Miguel Ángel Toro, a UPM researcher who has participated in the study, explains that “to know if it is possible to develop a genetic selection program that makes it possible to obtain a lineage that does not accumulate toxin, it is necessary to know that if mussels that accumulate little toxin are left, their children will also accumulate little toxin. This is only possible if the value of heritability is substantial.”
In the study, the researchers estimated the heritability and (genetic and phenotypic) correlations for the concentration of toxins both after a toxic episode related to the main diarrheal toxin (okadaic acid) and after a cleansing period in indoor facilities.
“We take advantage of the experimental design to estimate the same parameters for other features that are relevant to mussel production, such as those related to growth and colour,” explains Toro.
The results obtained showed that the heritabilities were moderate but significant, both after the periods of accumulation and detoxification, which indicated the possibility of reducing the concentration of toxins through improvement programs in mussels.
The growth-related traits also showed moderate heritabilities, while the colour showed a very high heritability, which makes them suitable for selection according to the demands of the producer and the consumer.
Interestingly, the growth-related traits showed negative genetic and phenotypic correlations with the concentration of toxins while those being colourful were positive, suggesting that larger and whiter mussels accumulate fewer toxins.
“The results of our study support the feasibility of breeding programs to address the main problems of the mussel industry, but this approach will determine a change in seed production, replacing or complementing the wild seed with the seed produced in the hatchery”, concludes Toro, who is a member of the Animal Production research group of the Higher Technical School of Agronomic, Food and Biosystems Engineering.