An international team of marine biologists has discovered a new species of the seahorse genus Hippocampus in the waters off southeast Japan.

Seahorses are a group (genus Hippocampus) of small fish belonging to the family Syngnathidae, which also includes pipefish and sea dragons.

These creatures are named for the shape of their head, which looks like the head of a horse.

They are found in shallow tropical and temperate waters throughout the world.

Unlike most other fish, seahorses are monogamous and mate for life.

Pygmy seahorses of the genus Hippocampus are diminutive in size (0.5-1 inch, or 1.36-2.6 cm, long).

They live in close association with octocorals, colonial hydrozoans, bryozoans, seagrass and algae.

They are morphologically distinct from the more numerous and larger species (0.9-14 inches, or 2.4-35 cm) of seahorses in possessing a single rather than paired gill openings and trunk brooding of their young.

Named Hippocampus japapigu, the newly-discovered species measures between 0.55 and 0.62 inches (1.4-1.6 cm) in length.

This pygmy seahorse was found by Dr. Graham Short from the California Academy of Sciences and his colleagues from the Pipefish Stickleback Specialist Group, the Kagoshima University Museum and the Port Stephens Fisheries Institute.

“Hippocampus japapigu is described based on three specimens collected from a mixed soft coral and algae reef at 36 feet (11 m) depth at Hachijo-jima Island, Izu Islands, Japan,” the researchers said.

Hippocampus japapigu occurs throughout subtropical southeast Japan and represents the fifth species of pygmy seahorse recorded in the country’s waters, according to the team.

The species’ description was published online this month in the journal ZooKeys.

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G. Short et al. 2018. Hippocampus japapigu, a new species of pygmy seahorse from Japan, with a redescription of H. pontohi (Teleostei, Syngnathidae). ZooKeys 779: 27-49; doi: 10.3897/zookeys.779.24799