This transparent animal lives on light with hundreds of live solar panels on its back

All plants and animals need energy. Animals usually eat other animals or plants for their energy. Plants, in turn, are usually able to obtain energy from sunlight through photosynthesis. But there are notable exceptions.

Take, for example, the binomial aquila. This small, worm-like animal lives in the ocean. Some Aquila species can generate energy in two ways. They form symbiotic relationships with single-celled microalgae that obtain energy from sunlight. They eat algae, but they don’t eat it. In fact, they attach it just below the surface of the skin and take advantage of the energy that algae generates through photosynthesis. Meanwhile, hundreds of microalgae are having a good time inside the aquila.

Appearances are deceiving
Aquila corpses At first glance, it is considered one of the most primitive species in the animal kingdom, but appearances can be deceiving. They are small, bilaterally symmetrical invertebrates measuring between 0.5 and 15 mm in size. This sea creature is a triploblast, which means it consists of three layers of cells. The outer layer is the epidermis (skin layer). They are covered with cilia that make movement possible. They have no cardiovascular system, but they do have a mouth through which they can absorb unicellular algae as food (or as a living solar panel). They also have a network of nerves and muscle cells that allow them to capture food and control movement with cilia.

Live solar panels
Biologists are very interested in the Aquila because it was one of the first animal groups on Earth and has an interesting ability to regenerate itself. As mentioned previously, some Aquila form symbiotic relationships with microalgae, including green algae and dinoflagellates that are commonly found near coral reefs. “Aquila species ingest these microalgae as food, but they do not digest the single-celled organisms. On the contrary, they give the algae a nice place just below the surface.” There, the microalgae are able to generate energy from sunlight, just like solar panels on roofs. Houses,” explains researcher Serati Riulwang of Hokkaido University in Japan.

Brightly colored algae
“Photosynthetic Aquila are found mainly in warm seawater. Therefore, we focused on the coast of southern Japan when sampling. We also encountered Aquila near Kochi, a Japanese region where warm water flows through the Kuroshio Current. Photosynthetic Aquila are sometimes difficult to detect Because they are microscopic, but under a microscope they can be clearly identified by their brightly colored algae.

Throughout 2022, Japanese researchers took samples of algae and sediment. The host and its symbionts were identified through DNA sequencing. Scientists selected symbiotic microalgae from their host and cultured them in order to better analyze them. This showed that Aquila contains all kinds of green algae among its members, called Tetraselmis. Until now, there was only one known species. Different types of dinoflagellates also appear to be floating in the Aquila. Most can be classified as Symbiodiniaceae, but some tetranoflagellates and dinoflagellates may be new discoveries.

Great interaction
The researchers were very surprised when they turned out to be able to identify an entirely new group of Aquila, all of which carry microscopic algae symbionts. “We found much more diversity in Aquila than expected,” said lead researcher Kevin Wakeman. “Even based on this data set, which only focuses on Japan, we can already say with certainty that there is a fascinating interaction between Aquila and microalgae. Our results can serve as a basis for future studies that delve deeper into these interesting ecological mechanisms.”

The science duo from Hokkaido will enjoy looking at the photosynthetic Aquila through a microscope in the near future. “It would be great if we could find out if we are really dealing with a completely new group of Aquila, but for that we need more genetic data and unambiguous visual data. Ultimately, I would like to use advanced imaging techniques to examine these Aquila at the Molecular.”