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Scientists discover new parasite species able to infect toxic microalgae in the Baltic Sea

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By Milthon Lujan

Spain – Parasitism is one of the most relevant biological mechanisms for the regulation of populations. Parasitism interactions are very common in nature, as are parasites. However, there are many places where parasites, which live on or inside another organism, causing them some harm or even killing them, have not yet been studied.

This is the case of the Baltic Sea, where until now there was very little information about the parasitic micro-organisms that live there and the interactions they establish with their hosts. Thanks to a group of researchers from the Institut de Ciències del Mar (ICM) in Barcelona and the Finnish Environment Institute (SKYE) who have spent the last few years describing and characterising the microalgae parasite species in this sea and others, that knowledge has been increased.

The researchers sampled microalgal blooms from the island of Kökar, located in the southeast of the Aland archipelago (Finland), in the northern Baltic Sea. Molecular techniques have allowed researchers to identify the coexistence of several previously unknown parasite species belonging to very distant phylogenetic groups, some of which closely resembling those found in the Mediterranean Sea.

Furthermore, thanks to the cultivation of these species in the laboratory, some of their particularities have been reported. These include the fact that, although they exclusively infect dinoflagellates, they have very different life strategies (forms of infection, development, etc.), but can coexist, i.e. they can be found at the same time and in the same place infecting different hosts.

In the description of the new species, also stands out the syringe-like structure of one of the species that has never been observed before. In the recent paper published in the journal Harmful Algae giving full details of the new species, the researchers stated that this structure is used by the parasite to attach itself to the cell it is infecting.

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“Everything is everywhere, the environment selects, as it is said in marine ecology. And the environment of these parasites is their hosts, which we went to look for to find the parasites”, explains the ICM researcher Esther Garcés, who is convinced that there are still many species to be discovered: “you just have to target your search to find them,” says Garcés.

Thanks to the different experiments carried out in the laboratory by the scientific team, it has also been possible to see that some of the parasites are capable of infecting harmful microalgae, the proliferations of which can be, depending on the species and genus, particularly toxic, causing serious socio-economic problems. These episodes occur at certain times of the year, when environmental conditions are optimal for the growth of specific species of algae, and can, in some cases, literally stain beaches with unusual colours.

For future research, the researchers hope to be able to describe in detail when the species described now are most abundant, what conditions optimise their propagation, how specialist or generalist they are, how dependent they are on their hosts and even what do parasites do when they cannot find any host.

“Knowing the species living in a given environment is the basis for studying how the different components of the community interact and, therefore, for understanding how the ecosystem works”, concludes ICM researcher Albert Reñé, who is also involved in the research.

Reference Articles:
Karpov, S. A., Reñé, A., Vishnyakov, A. E., Seto, K., Alacid, E., Paloheimo, A., … & Garcés, E. (2021). Parasitoid chytridiomycete Ericiomyces syringoforeus gen. et sp. nov. has unique cellular structures to infect the host. Mycological Progress, 20: 95–109. 

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Alacid, E., Reñé, A., Gallisai, R., Paloheimo, A., Garcés, E., & Kremp, A. (2020). Description of two new coexisting parasitoids of blooming dinoflagellates in the Baltic sea: Parvilucifera catillosa sp. nov. and Parvilucifera sp.(Perkinsea, Alveolata). Harmful Algae, 100: 101944. 

Source: Institut de Ciències del Mar (CSIC)

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