New species with six eyes discovered on a rotten log in a Japanese forest

A bright blue, six-eyed springtail found on Tsushima Island in Japan turned out to be a new species. According to researchers, the springtail is about 0.06 to 0.07 inches long and carries six eyes in two neat rows.

The work was led by Hiro Kasai of Kindai University in Nara, Japan. His research focuses on collembola, small six-legged soil animals that often jump.

Springtails are tiny hexapods that are common in soils worldwide. They feed on fungi and decaying matter and help recycle nutrients in the ground.

Four new Paranura species

“In the present study, we describe four new Paranura species,” wrote Kasai. Paranura tsushimaensis spans roughly 0.06 to 0.07 inches and shows six black eyes, three on each side.

Scientists collected two females, three males, and one juvenile from rotten branches in an evergreen forest.

On Sado Island in Niigata, six females of Paranura nakamurai were found in dead branches. This yellow-white species ranges from about 0.03 to 0.06 inches long.

On Mount Syakagatake in Nara, the team collected five females and one male of the species Paranura alpicola. It is yellow with a thick body and measures about 0.05 to 0.09 inches.

From 2020 to 2022 in Nara, surveys uncovered several specimens of Paranura convallis. The orange species is short and stout, has six eyes, and measures roughly 0.06 to 0.09 inches in length.

Names carry stories

The new names honor places and habitats where the animals were collected. Paranura tsushimaensis references Tsushima Island, and convallis reflects a mountain valley site.

Paranura alpicola takes its name from the high mountain forest where it was found on Mount Syakagatake in the Kii Mountains.

Paranura nakamurai honors Kahito Nakamura, who discovered and collected the species.

Paranura species clues

The striking body colors of these springtails are not just for show. Pigmentation in collembola, tiny soil arthropods, often helps protect against light exposure or fungal infection.

In the deep shade of forest litter, such variation may also mark differences in microhabitat or diet.

Morphological diversity within Paranura hints at long isolation between populations. Subtle differences in body size, setae pattern, and eye number reflect adaptation to different moisture levels and decay stages of fallen wood. 

These traits help scientists understand how environmental gradients drive evolution even in animals smaller than a grain of rice.

Why dead wood matters

Many springtails are saproxylic, species that depend on dead wood for food or shelter. A U.S. Forest Service paper reported that saproxylic beetles are highly sensitive to reductions in dead wood.

“Saproxylic beetles are highly sensitive to forest management practices that reduce the abundance and variety of dead wood,” wrote Michael Ulyshen with the U.S. Forest Service.

Specimens moved out of a Berlese funnel, a setup that dries leaf litter and guides tiny animals into a vial. The blue species emerged from an evergreen forest sample collected on Nov. 27, 2022 on Tsushima Island.

After photography, the team preserved specimens in ethanol and mounted slides for microscope work. They compared key morphology, visible body traits such as eye number and setae patterns, against described species.

Bigger picture for tiny animals

The genus stretches across Asia and the Americas, shown in an article that documented species in Oregon and the Russian Far East. Its diversity keeps growing.

Before this survey, only three Paranura species were known from Japan, based on earlier records. Fieldwork aimed at dead wood now adds four more, each from a different site.

Springtails help break down litter and spread microbes that drive soil cycles. Many are detritivores, animals that feed on dead material and associated microbes.

Lessons from Paranura species

These animals sit low in food webs, yet changes to their habitat can ripple upward. Dead wood patches of different sizes support different invertebrates, which increases diversity across a forest.

A European review found that these links are strong in temperate woodlands. Protecting fallen branches during logging and park maintenance can keep these microhabitats intact.

Targeted searches across seasons, elevations, and islands will likely uncover additional species within this genus. Japan’s varied mountains and coastlines create many microhabitats, small environmental pockets with distinct moisture and fungi.

Taxonomy advances step by step when teams publish careful descriptions and keys for identification. This work gives future surveyors a map for spotting species that were hiding in plain sight.

The study is published in the journal Zootaxa.

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