Altruism towards descendants: A study reveals d


Image: Diatoms and other planktonic organisms under the microscope
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Credit: MOTax-SZN

Diatoms, unicellular algae typically anchored in a siliceous cell wall, generally act as opportunistic organisms that can reproduce uncontrollably under favorable conditions, but can also make altruistic decisions for the benefit of the community.

A new study led by Mariella Ferrante from the Zoological Station Anton Dohrn in Naples (SZN) in collaboration with SISSA from Trieste and CEA from Grenoble focused on the marine diatom Pseudo-nitzschia multistriata, showed that when cells of opposite mating types meet and are in the right conditions for sexual reproduction, only a small fraction participates in the sexual event, while the rest of the cells block their own growth, restrict their activities, and reduce the absorption of Nutrient. This phenomenon occurs with nutrient abundance and thus represents a paradox for microalgae, which normally compete for environmental resources.

The research, conducted through genetic, physiological and numerical analysis, was funded by the Gordon and Betty Moore Foundation and saw the participation of molecular and cellular biologists, ecologists, oceanographers, bioinformaticians and modelers.

Invisible but fundamental

Diatoms are unicellular algae, microscopic and invisible to the naked eye, that live in suspension in the waters of our oceans, rivers and lakes. Living in oceanic waters, these single-celled organisms are the basis of marine food webs and drive global biogeochemical cycles. They also produce much of the oxygen we breathe through photosynthesis.

dr Rossella Annunziata of SZN, first author of the work, says: “The reason why a large proportion of diatoms during a sexual reproductive event choose to reduce nutrient intake and squander the opportunity to grow using available resources is because Advantage that the daughter receives Cells that find a more nutritious environment that favors the growth of the new generation and facilitates the development of the community”. The coordinator of the study, Dr. SZN’s Mariella Ferrante, adds: “It is a very interesting biological model that highlights subtle life-cycle control in diatoms. This discovery prompted us to review current theories of plankton ecology, which often consider resource availability alone, to study the reproductive success of unicellular microalgae. Our results demonstrate the existence of complex biological mechanisms behind the phenomena involving planktonic organisms.”

Studying plankton to understand evolution

Prof. Remo Sanges from SISSA, who coordinated the bioinformatics analysis, comments: “It was fascinating to observe how protozoa evolved life strategies reminiscent of the well-known parental care found in wildlife. These results support the notion that relatively simple organisms are actually capable of complex behaviors.”

One of the goals of evolutionary studies is to understand the selective forces and demographic mechanisms that drive population dynamics in the face of ecological challenges posed by interactions with other organisms and by environmental variability. These types of studies are very important as they help shape the ecological niches of species and describe and understand the structure of plankton communities.

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