Plankton horror story : How algae eat each other

(ORDO NEWS) — When it comes to “herbivores,” we usually think of deer, guinea pigs, or, at worst, grasshoppers, but certainly not algae.

However, in the wonderful world of marine plankton, the rules that apply on land are turned inside out: microalgae invade the cells of others to engulf them from the inside.

Imagine a tiny creature that invades an alien organism to devour it from the inside, absorb the genetic material and leave behind only an empty shell.

Creepy as it sounds, this is exactly what happens to the tiny alga Scrippsiella acuminata when it falls prey to the Amoebophyra parasite.

What is most surprising, both the host and its parasite are dinoflagellates , which are also called “dinophyte algae.”

Formally, they do not belong to plants, but many representatives of this type are photosynthetic organisms, indistinguishable in their way of life from, say, duckweed.

An international team of researchers led by Johan Deccele and Laure Guillou have studied in detail the process of interaction between the parasite and its host.

The truth turned out to be terrifying: even after Amoebophyra invades the host cell and begins to absorb its nutritious genetic material, it continues to photosynthesize quietly, not noticing its own death.

Using 3D electron microscopy and transcriptomics, the scientists were able to trace the process of host uptake by the parasite step by step, at nanoscale resolution.

It turned out that Amoebophyra does not touch mitochondria and plastids until the last moment , so that even when all the DNA of Scrippsiella acuminata becomes food for the voracious parasite, the host cell continues to provide it with energy.

Only after the multiplied Amoebophyra cells break through the cell membrane and go outside, going in search of the next victim, does the absorbed alga finally die: fortunately, “zombie algae” do not swim in the ocean.

Plankton horror story How algae eat each other 2
The process of infection of two cells of microalgae: the host chromosomes are shown in bright blue, and in the algae on the right they have already become food for the parasite

The new study not only sheds light on the nature of the interaction of a tiny parasite with its no less tiny host, but can also significantly expand our knowledge about the functioning of planktonic ecosystems, the most important photosynthetic system on our planet, the Earth’s “lungs” that ensure the carbon cycle in the ocean.

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