They find a new symbiotic relationship between aquatic species linked to the presence of omega-3 in aquaculture

VALENCIA, 25 Oct. (EUROPA PRESS) -

A study carried out by members of the Group of Auxiliary Species in Aquaculture, Larviculture and Ecotoxicology, of the Torre de la Sal Aquaculture Institute (IATS) - center of the Higher Council of Scientific Researchers (CSIC) in Castellón - reveals the existence of an association ecological between small crustaceans called gammarids, used as food for aquatic animals, and a freshwater microorganism (badelloid rotifers).

According to the study, these two organisms have had to converge evolutionarily, as evidenced by comparisons between gene sequences from samples extracted by the IATS-CSIC team.

The mechanism by which these small crustaceans obtain omega-3 fatty acids, essential in the diet of farmed fish, is thus discovered. The research, published in the journal 'Open Biology', is part of Alberto Ribes Navarro's doctoral thesis.

In search of sustainability, the aquaculture industry continually explores alternative ingredients to meals and oils produced from industrial fishing. Although there are substitute feeds of terrestrial origin, those of marine origin have a superior nutritional profile due to their richness in omega-3.

The intensive production of marine invertebrates such as gammarids can help meet nutritional quality objectives if they are included as ingredients in feed, which is why it is very common to carry out nutritional profile studies. It is therefore essential to clarify the capacity for synthesis of omega-3 fatty acids in these invertebrates. The IATS-CSIC team has been a pioneer in carrying out molecular studies in gamarids that have made it possible to understand this biosynthetic capacity.

Previously published research suggested that freshwater gammarids had developed the ability to produce omega-3. The presence of this nutrient in freshwater ecosystems is minimal, so its acquisition in this environment "is an evolutionary challenge," says Alberto Ribes.

Saltwater mammals cannot produce omega-3 either, although they acquire it more easily from the ecosystem where they live, rich in these compounds, through their diet based on zooplankton and microalgae, "just as humans acquire omega-3 , through fish and seafood," explains the IATS-CSIC doctoral student.

Through the gene expression study, IATS-CSIC researchers have shown that these small freshwater crustaceans do not have "all the necessary gene machinery" for the production of omega-3, so they must obtain these nutrients through other ways. Through an evolutionary study "we observed that the sequences we found in the transcriptomes of freshwater gamariids were not typical of the gamariid, but rather of a freshwater aquatic microorganism called rotifer," explains Ribes.

Rotifers are microscopic animals that adhere to the exoskeleton of the gammarid. The ecological association is important because it has been observed that, regardless of geographical location, "all the freshwater gammarids studied contain rotifers in their exoskeleton, but the most surprising thing is that they all have the same types of rotifers from the zoological class Bdelloidea" clarifies the IATS-CSIC researcher.

These rotifers are characterized by having all the genes necessary to produce omega-3, "very possibly this association transcends the already wide geographical scope of this study, and is widespread," reflects Alberto Ribes Navarro.

Evolutionarily, these two organisms have had to converge from an ecological point of view and "establish some symbiotic relationship, like that of the remora fish and the shark, or that of the clown fish and the anemone," points out the doctoral student. This gammarid-rotifer association demonstrates that it is a mechanism that "produces benefits, as observed through its proliferation throughout a large part of Eurasian freshwater bodies."

The significant novelty of the research lies in the "evidence that the potential for omega-3 synthesis comes from the rotifer and not from the gammarid, which opens the door to interesting questions such as the potential contribution of omega-3 from the former to the latter." "concludes Alberto Ribes Navarro.