В пруду Императорского дворца в Токио обнаружена новая водоросль Volvox sagami

By KAZUHIRO FUJITANI/ Staff Writer September 2, 2026 at 07:00 JST The Imperial Palace moat in Tokyo is home to a new species of Volvox, a genus of algae, known for forming spherical colonies that bring neatness and symmetry to the messy microscopic world. The new species, Volvox sagami, was identified in water samples by researchers from Hosei University and Osaka Institute of Technology. They matched it to specimens previously found in Lake Sagami and Lake Tsukui in Kanagawa Prefecture. The species was formally described in the journal of the International Phycological Society and given its name, abbreviated to V. sagami. Volvox is a green alga found only in freshwater. Individual algae form a colony known as a green pearl. Eleven species of Volvox are known to exist in Japan. Four of these are considered endemic. In 2024, a team led by Noriko Ueki, a professor of evolutionary biology at Hosei University, found Volvox in samples taken from the outer moat of the Imperial Palace in central Tokyo. It was the first reported sighting of Volvox in the capital since 1896. NEW SPECIES Like many algae, Volvox normally reproduces asexually. It switches to sexual reproduction when environmental conditions change, such as when temperatures fall or its aquatic habitat dries out. Eggs and sperm fuse to form zygotes, which develop thick protective walls that enable them to survive the period of hardship, such as winter or drought. Ueki and her colleagues matched the sample from the Imperial Palace moat with the Volvox found in Lake Sagami. But they faced a problem. The Sagami samples were long known to be similar to Volvox ferrisii. The differences seemed insufficient to consider them different species. That changed when the researchers conducted a detailed comparison with V. ferrisii. They found a host of differences, including at the reproductive level. For one, the zygotes of the Sagami individuals were larger, while V. ferrisii produced a greater number of zygotes per individual. Furthermore, the zygotes were covered with numerous short spines, whereas the spines of V. ferrisii were longer and more sparsely distributed. One criterion of a species is whether its members can interbreed with individuals outside the group. Genetic analysis confirmed that there is no genetic exchange between the two. The Sagami sample was therefore determined to be biologically distinct and therefore it was described in the journal as a new species, V. sagami. Ueki finds the Volvox and its colonies fascinating. It “evolved into a multicellular life only relatively recently,” she said. As daughter colonies develop inside a parent Volvox, they turn inside out, relocating their flagella from the inner surface to the outer surface so they can propel themselves through water. “By studying forms of cellular movement that do not exist in single-celled organisms, we can observe the process by which multicellular organisms evolved step by step,” she said. In Japan, Lake Biwa is the only place where V. sagami and V. ferrisii have been confirmed to coexist. Ueki noted that the lake may provide clues to understanding how the two species diverged from one another. The study was published in the International Phycological Society journal Phycologia (https://doi.org/10.1080/00318884.2026.2683158). A peek through the music industry’s curtain at the producers who harnessed social media to help their idols go global. A series based on diplomatic documents declassified by Japan’s Foreign Ministry Here is a collection of first-hand accounts by “hibakusha” atomic bomb survivors. Cooking experts, chefs and others involved in the field of food introduce their special recipes intertwined with their paths in life. A series about Japanese-Americans and their memories of World War II