Scientists have revived a forgotten genus of algae that lives in marine animals

In the century before last, scientists discovered mysterious yellow cells inside anemones, corals and jellyfish.

It turned out that they are not part of the body of theseanimals. 140 years after the discovery of yellow cells, it turned out that they belong to six previously not described species. The research is published in the European Journal of Phycology.

At the end of the 19th century, biologist Karl Brandt rankedyellow cells to the genus Zooxanthella. A year later, another scientist, Patrick Geddes, made a new discovery. It turned out that cells are not genetically related to living things in which they were found. He referred them to the new genus Philozoon. Over time, the scientific contributions of Geddes were largely forgotten, and the genus name Philozoon was never used.

Over the years, scientists have found that these microorganisms are photosynthetic dinoflagellates or unicellular algae that exist in symbiosis with marine inhabitants.

Now, more than a century after publicationarticle by Geddes, an international team of researchers revised these "yellow cells", which over time were identified as photosynthetic algae in the Symbiodiniaceae family.

In the new work, the specialists carefully studiedyellow cells, using genetic data, geographic data and morphology to analyze exactly where they are in the large tree of biological species that live on Earth. It turned out that the yellow cells, samples of which were collected by scientists in different parts of the world, belong to six previously not described species. Despite their external similarity, they are very different and live in different parts of the world, including in cold waters.

The ability of these Philozoons to survive in a widerange of temperatures is probably related to their diversity in the cooler periods of the Late Pliocene and recent epochs of the Pleistocene. It is this adaptation to the range of temperatures that is likely to protect them and the animals with which they are associated from the effects of climate change.

“Each species of symbionts demonstrates high loyalty to the host of certain species of sea anemone, soft coral, stony coral and jellyfish with rhizostomy,” the scientists note.

Careful identification and categorization of these symbiotic algae is essential to understanding the biology and evolution of marine animals that depend on these organisms for their survival.

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