A transparent jellyfish scooped out of the water off a dock in Tanabe Bay, Wakayama, Japan, in 2018 by a 13-year-old named Ryoya Sugimoto has been formally described as a new species, Orchistoma integrale, in a paper published February 28, 2025, in the journal Plankton and Benthos Research. The 14-page description, spanning pages 62 to 75 of the journal’s twentieth volume, makes Sugimoto — now a university student — the lead author of a paper naming only the fifth known species in its genus.

A dockside observation that didn’t match the books

Sugimoto was already an enthusiastic amateur jellyfish-watcher when he spotted the animals drifting near the docks of Tanabe Bay on the Kii Peninsula. According to an account he gave to Karmactive, he had committed the jellyfish species known from Japan to memory through field guides, and the specimens in front of him did not match anything he recognized. “I remembered all the jellyfish species of Japan from books I’d read, but these were morphologically different from any species I knew,” he said. Rather than let the observation go, he collected several dozen individuals to examine at home.

Identifying a hydromedusa down to genus and species requires close attention to structures that are easy to miss with the naked eye — the arrangement of tentacles and tentacle bulbs around the bell margin, the shape of the manubrium, and the pattern of gonads along the radial canals. Sugimoto’s specimens carried a distinctive combination of these features that didn’t fit any described species, so he sought outside expertise, eventually reaching Allen G. Collins, a zoologist at the NOAA Fisheries National Systematics Laboratory, who is also affiliated with the Smithsonian National Museum of Natural History and has spent decades studying hydrozoans.

Seven years from dock to description

Turning a promising find into a formally recognized species is a slow process, and the gap between Sugimoto’s 2018 collection and the paper’s 2025 publication reflects that. Confirming a new species means ruling out every existing description in the relevant family, sectioning and photographing diagnostic tissue, and — ideally — sequencing DNA to corroborate what the anatomy suggests. The finished paper, “Orchistoma integrale sp. nov. (Hydrozoa, Orchistomatidae), a new species of hydromedusa with the first record of the genus from the Northwest Pacific,” credits three authors: Sugimoto, Takato Izumi of Fukuyama University, and Collins. By the time it appeared, Sugimoto was a student at the University of Tokyo, roughly seven years and, by most outlets’ reckoning, about seven years older than when he first netted the animals.

The paper places the new species in the family Orchistomatidae, a small and monotypic hydrozoan lineage — meaning the family contains only the genus Orchistoma — that before this description held four recognized species worldwide. Orchistoma integrale is the fifth, and its discovery carries a geographic significance beyond the new name: it is the first confirmed record of the genus Orchistoma, and of the family Orchistomatidae, anywhere in the Northwest Pacific, including Japanese waters. Every previously known species in the genus had been recorded from other ocean basins, so finding one thriving in a bay on Japan’s Pacific coast extends the family’s documented range substantially.

What makes it “integrale”

The species name integrale nods to the shape of the animal’s gonads, which curl into a form resembling the mathematical symbol for an integral (∫) — the resemblance Sugimoto drew on to coin the Japanese common name integuraru-kurage, or “integral jellyfish.” Those prominently curled gonads, along with scattered nematocysts on the umbrella, are also the anatomical features the paper cites to distinguish Orchistoma integrale from its four congeners. NOAA’s own writeup, published as “Meet the Integral Jellyfish,” frames the find as a case study in how far a sharp-eyed amateur observation can travel when it lands in the hands of a specialist willing to follow up.

The type material now has an institutional home reflecting the international nature of the collaboration: the holotype is deposited at Japan’s National Museum of Nature and Science in Tsukuba, with additional preserved material held at the Smithsonian National Museum of Natural History in Washington, D.C. Depositing specimens in accessible public collections is standard taxonomic practice — it lets future researchers re-examine the physical evidence behind a species description rather than relying solely on the published photographs and measurements.

A small animal with an outsized research question

Hydromedusae like Orchistoma integrale are the free-swimming jellyfish-like stage of hydrozoans, a group of small predatory animals related to corals and sea anemones. Most species in this group are only centimeters across, nearly transparent, and easy to overlook in open water — which is precisely why citizen naturalists with patience and a net can still turn up animals that have escaped formal description. Collins, in comments reported by Karmactive, called the northwest Pacific record itself the most striking part of the find: “This discovery is surprising in the sense that we’ve never seen a species from this family in the northwest Pacific Ocean.”

Whether Orchistoma integrale is a rare animal, a longstanding resident of Japanese coastal waters that plankton surveys had simply missed, or a recent arrival from elsewhere carried by currents or shipping remains an open question the paper does not resolve. Determining that would require broader sampling across the region’s coastline and, potentially, genetic comparison with the four other described Orchistoma species to establish how closely related the northwest Pacific population is to those found elsewhere.

The value of a careful amateur

Sugimoto’s path from a dockside sighting to a peer-reviewed species description sits within a long tradition of taxonomy that depends on people outside professional research institutions noticing something and following through. Plankton, in particular, is undersampled almost everywhere relative to how much diversity it likely contains, since routine surveys tend to prioritize commercially or ecologically prominent species over small gelatinous organisms that are hard to preserve and identify.

Sugimoto has described the process as one that connected him with researchers across a language and career-stage gap, telling Karmactive, “By using jellyfish as a common language, along with English, I have come to know the joy of connecting with others across borders, sharing my passion and interests.” The published description of Orchistoma integrale stands as the formal, citable record of that connection — and, for the genus Orchistoma, as the first evidence that its range reaches as far as the Northwest Pacific.