April 15, 2024

In Japan, stories were told of forest-dwelling magical spirits called kodama since ancient times. Over the centuries they have taken many forms: sometimes they are invisible, sometimes they look like trees. The Studio Ghibli animated movie Princess Mononoke depicted kodama as round little humanoids with rotating bobble heads. Now, a genus of miniature squid has been named in honor of the kodama and their role as nature’s guardians.

“If you see them, it’s a sign that the ecosystem is healthy,” says Jeff Jolly of the Okinawa Institute of Science and Technology, referring to Kodama jujutsuthe dwarf squid that he and a team of scientists and underwater photographers found on coral reefs in Japan and described in a 2023 paper.

“They are very small,” said Jolly, “the size of your pinky nail.” The squid are members of the Idiosepiidae family, which are the ocean’s smallest cephalopods and are dwarfed by their cousins, the octopuses, squids and cuttlefish. The common name for the species in English is the Hannan’s pygmy squid after Brandon Ryan Hannan, a diver and photographer who helped find and collect them. They are not easy to spot because they are incredibly small and nocturnal.

Hannan’s dwarf squid (Kodama jujutsu) taken in nature.

A second pygmy squid species, the Ryukyuan dwarf squid, Idiosepius kijimuna, was discovered in the seagrass meadows around the Ryukyu Islands of southern Japan, including Okinawa. This one is named after mischievous creatures from Okinawan mythology, the kijimunā, who live in banyan trees and are skilled fishermen. These pygmy squids were already known, but upon closer examination they turned out to be a separate species.

Jolly and colleagues kept the two pygmy finfish species in aquariums, where they were much easier to keep alive compared to larger cephalopods. Octopuses are notoriously antisocial in captivity and tend to attack each other.

By taking a closer look at the pygmy squid, the team observed behavior that would have been difficult to follow in the wild. “They spend a lot of time just sitting around,” said Amanda Reid, a taxonomist at Australia’s Commonwealth Scientific and Industrial Research Organisation, who helped identify the new species while working at the Australian Museum. She describes a sticky patch on their backs that glues them to sea grass blades, leading a colleague to call them “sucker-bum squid”. Once stuck in place, the squid waits for shrimp to float within grasping range.

Jolly saw Hannan’s pygmy squid hunting shrimp much larger than them, which inspired him to give them their species-specific name, jujutsu, to the martial arts. “The principle of jujutsu is that a small person can attack a bigger person,” he says. “You hold them and wrestle them and control their back, which is what the squid does.”

The pygmy finfish spawned in captivity. Each species performs a distinct and complex courtship ritual, either face-to-face or with the male below and behind the female. “They buzz like bees while they do it,” says Jolly.

Jolly has successfully raised two generations of Hannan’s dwarf squid, which he thinks is a first for this squid family. When they hatch, the young are large, relatively speaking, and can immediately hunt shrimp. They only live for two or three months.

The two new species bring the total number of known pygmy finches to eight, living in different parts of the Pacific Ocean. “I think there will probably be more species to be described. There are a few from northern Australia that I’m pretty sure are new species, so we’ll see,” says Reid. “This is not the end of the story as far as these little animals are concerned.”

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