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| On the left, the organism “Hatena” possesses a green algae body as a symbiotic entity, with a tail protruding outside its cell membrane. On the right, Hatena divides into two daughter cells, one transparent and one inheriting the green symbiotic material. The transparent daughter cell will go out to forage and “kidnap” a new algae cell. |
Japanese scientists have observed a unicellular organism (consisting of a single cell) devouring and merging with an even smaller plant body to create a source of stored energy.
According to the research team, this organism appears to be in the process of endosymbiosis—a process where one organism merges with another, resulting in a new form of life. They believe this may represent the evolutionary pathway for many modern animal and plant species today.
This discovery further supports the long-discussed hypothesis that chloroplasts—the structures within plant cells responsible for converting sunlight into energy—are actually independent organisms that have been “kidnapped” in a similar manner.
Similarly, the research team, including Noriko Okamoto and Isao Inouye from Tsukuba University, believes that other components of cells—the building blocks of all modern animals—originated from “trapped” bacteria.
The newly discovered organism, dubbed Hatena (or The Mystery), is a flagellate that moves its body by propelling its long tail. It shares characteristics with both plants and animals, but at a certain stage of its development, it resembles a predator. At another stage, Hatena contains a green algae body capable of photosynthesis within itself. During this phase, it divides into two daughter cells—one green and one colorless. The colorless daughter cell develops a foraging tool and will eventually engulf another green algae cell.
The green algae cell, also known as the symbiont, belongs to the well-known algae group Nephroselmis, which is quite common in nature. It also has a flagellum but loses it upon being engulfed by the colorless cell. Simultaneously, its outer membrane degrades, retaining only the nucleus and other cellular components such as chloroplasts and mitochondria.
The green portion then expands and provides nutrients to the now-degenerated predator that has lost its complex foraging apparatus.
The researchers collected several transparent predatory daughter cells and fed them with another type of algae, a relative of Nephroselmis. “Although the prey was engulfed and not digested, it did not undergo the transformation as mentioned above, indicating that the interaction is specifically differentiated with only one type of algae.”
Now, the research team will investigate whether these two species exchange genes with each other—a step considered crucial in the evolution of algae and higher plant species.
T. An (according to IOL)
