Fish Illustrations > Seahorses

Approximately 46 species belong to genous Hippocampus. They are divided into two major groups: pygmy seahorses (9 species), which are about 2 cm in length even as adults, and "large species" (37 species), which are more than 3 centimeters in length. In Japan, about 3 species of pygmy seahorse and about 9 species of "larger species" inhabit.

Seahorses distributed in Japan

crowned seahorse タツノオトシゴ Hippocampus coronatus

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 13 cm (usually around 6 cm). Endemic to Japan. They inhabit from Nagasaki to Tokyo Bay. They live mainly in algae beds. Adults are characterized by a high crown that bends back and wing-tip spines extending laterally from the dorsal fin base. Body color varies from light reddish brown to dark reddish brown, often with thin whitish stripes and small black spots. Pregnant males often have fine black and white spots on their brood pouches. Spawning season is spring to summer. IUCN data deficient (DD).

Shiho's seahorse ハナタツ Hippocampus sindonis

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 10 cm. Distributed in the northwestern Pacific Ocean (southern Japan and southern Korea). There are no wing-tip spines at the dorsal fin base (⇔ H. coronatus has wing-tip extending laterally from the dorsal fin base). The body color is diverse, such as bright red and yellow, and there are fleshy skin filaments on the head and trunk. The crown is high. Females often have fleshy skin filaments over the eyes and crown, while males often have a smooth crown. Found in algae beds and sandy bottoms. IUCN least concern (LC).

thorny seahorse イバラタツ Hippocampus histrix

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 17 cm. Distributed in the western Pacific, mainly from Japan to Indonesia. In Japan, it can be seen in the Izu Peninsula and Wakayama Prefecture. Found on sandy bottoms with soft corals and sponges and rocky reefs with algae at depths of 15-40 m. They vary greatly in body color, from bright yellows and browns to reds and greens, depending on their habitat. It is characterized by having many spins on its body and a very long snout. IUCN vulnerable (VU)。

Japanese seahorse サンゴタツ Hippocampus mohnikei

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Relatively small seahorse with a maximum total length of 8 cm (usually around 5 cm). Distributed in the southern area of the Japan Sea from the Kyushu region to the western part of Honshu and the Izu Peninsula. Mainly found in eelgrass beds. Body color varies from light brown to dark brown or black, with scattered whitish spots. They camouflage themselves well in their habitat and are hard to find. Adult fish have a low crown, a short snout, and an elongated tail. Spawning season is spring to autumn. IUCN vulnerable (VU)。

three-spotted seahorse タカクラタツ Hippocampus trimaculatus

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 22 cm. It is found in various areas in Asia including Japan (India, Cambodia, China, Hong Kong, Taiwan, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, Thailand, Vietnam, etc.). In Japan, it is distributed southern area from Aomori Prefecture. Inhabits algae beds and sand bottoms in shallow coastal reefs. There are a pair of backward-pointing spines above the eyes and below the operculum. Body color varies from gray to dark brown or black, with three black spots on the dorsal surface. However, it is sometimes unclear. Juvenile fish have a relatively large crown, but the crown becomes inconspicuous in adult fish. Spawning season is from May to June. IUCN vulnerable (VU)。

great seahorse オオウミウマ Hippocampus kelloggi

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 28 cm. Distributed in subtemperate to subtropical regions from southern Japan to the China Sea and the Philippines. The trunk is long and the snout is wide. The body color is brown to black with thin white lines and small spots. Some juveniles and females are cream or yellow. Juveniles of 10 cm or less have long and slender bodies, and small white spots appear near the head as they grow. Common on slopes exposed to strong currents at depths of 20 m or more. It can also be seen in relatively deep waters at a depth of 120 m. IUCN vulnerable (VU)。

yellow seahorse クロウミウマ Hippocampus kuda

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 18 cm. Widely distributed in the Indo-Pacific (Maldives, Sri Lanka, Andaman Sea, Singapore, western Indonesia to Bali). In Japan, it is distributed in the Ryukyu Islands. The body color is dull reddish brown to black. Males have many black spots all over their bodies, while females have bright yellow or dark brown spots. Juveniles have a short snout, but it lengthens as they mature. It is also found in the brackish waters of estuaries. IUCN vulnerable (VU)。

The pygmy seahorse is a tiny seahorse that was discovered by chance in New Caledonia by being attached to a coral that was collected for an aquarium display. Although pygmy seahorses are classified in the genus Hippocampus, they are considered to be diverged early during the evolution of the genus due to their distinctive morphological features, such as male brood pouches locate on the body cavity, the presence of a single gill opening (in other seahorses there are two), etc.

pygmy seahorse ピグミーシーホース Hippocampus bargibanti

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 2.4 cm. Distributed in the Indo-West Pacific Ocean (Japan, Indonesia, Australia, Vanuatu, etc.). Inhabited within Octocorallia, and camouflaged to the Octocorallia. Two patterns of body color are known. Pale gray or purple individuals with pink or red circular spikes are found in Muricella plectana. Yellow individuals with orange circular projections are found in Muricella paraplectana. Juveniles attach to a variety of hosts, but breeding seems to favor red polyps, which usually grow at depths greater than 20 m. IUCN data deficient (DD).

Seahorses distributed in Oceania

pot-bellied seahorse ポットベリーシーホース Hippocampus abdominalis

Order Syngnathiformes, family Syngnathidae, genus Hippocampus. Maximum total length 35 cm (usually around 18 cm). Mature individuals can be seen from 8.7 cm. Distributed in Australia and New Zealand. Females have a wide body, while males are slender but widen as they grow. The length of the snout varies, but is usually about the same as the length of the operculum. Body color varies depending on the depth and environment in which they live, ranging from whitish to dark brown, yellow, and orange. Some individuals have conspicuous black spots. The tail has alternating dark and light stripes of varying widths. The dorsal fin has many small spots. Inhabits seaweed beds and sponge layers up to a depth of 100 m. IUCN least concern (LC).

References

Kuiter RH (2009) Seahorses and their relatives. Aquatic Photographics, Seaford, Australia.
Short G, Smith R, Motomura H, Harasti D, Hamilton H (2018) Hippocampus japapigu, a new species of pygmy seahorse from Japan, with a redescription of H. pontohi (Teleostei, Syngnathidae). ZooKeys 779: 27-49.
Han SY, Kim JK, Kai Y, Senou H (2017) Seahorses of the Hippocampus coronatus complex: taxonomic revision, and description of Hippocampus haema, a new species from Korea and Japan (Teleostei, Syngnathidae). ZooKeys, 712: 113–139.