Probably the most well-known pygmy seahorse is the pink Bargibant’s camouflaging in on a gorgonian seafan. It was the first pygmy to be known to science and it will be the first one many divers will see. It was for me too.
Pygmy seahorses are all very well camouflaged and tiny which makes them difficult to find, especially when looking for one for the first time.
When you do eventually see it it’s even more rewarding. They are just so cute with the round body and head as well as a short snout. They seem to be baby seahorses but the largest pygmy will never grow bigger than 27 mm and the smallest one 14 mm. Measured from the tip of the tail to the snout.
Not just small seahorses
Pygmy seahorses are not just small versions of the larger seahorses. Like the bigger seahorses the males carry the young but in the trunk and not in a pouch at the tail. So the pygmies actually do look pregnant with a big belly. The babies are released into the ocean where they swim for a planktonic phase in the open water before settling down on a seafan or on the reef (1).
The other main difference is the gills. Seahorses have two openings on the sides of their head while pygmies have a single opening at the back of their head.
Most of the pygmy seahorses are found in the coral triangle which includes the Philippines, the eastern parts of Indonesia and Malaysia, Papua New Guinea, Timor Leste and the Solomon islands. Some pygmies, like the Bargibant’s can be found down to the Great Barrier Reef and to the east out to Palau. Exceptions are the Japanese and the Coleman’s pygmy seahorse.
The Bargibant’s pygmy seahorse was to first to be described in 1970, six additional species have been described since 2000 and one remains to be described.
The Bargibant’s pygmy seahorse (Hippocampus bargibanti)
A scientist named George Bargibat discovered the first pygmy seahorse by chance when he collected a sample of a gorgonian seafan for a museum.
The maximum size is 27 mm and the color is often pink but can be more red or purple as well as yellow depending on the color of the gorgonian fan it is living on.
Denise’s pygmy seahorse (Hippocampus denise)
Like the Bargibant’s pygmy the Denise’s stays its whole adult life on a single seafan. While the Bargibant’s always live on the same species of gorgonian, H. denise can live on different types of gorgonian genera.
After choosing a seafan to live on the baby pygmy gets its final color which can range from yellow to orange or pink and body texture adapting to its new house. It grows to a maximal size of 24 mm.
Bargibant’s and Denise’s pygmy seahorses are the only ones that are bound to a seafan as habitat which makes them more fragile if there is destruction of the gorgonians through fishery, anchors and scuba divers. Read more about how to photograph the gorgonian-associated pygmy seahorses without harming them or their habitat (how not to kill the pygmy seahorse).
One more species is bound to a single habitat;
Walea soft coral pygmy seahorse (Hippocampus Waleananus)
This pygmy has so far only been found next to Walea island in the Togeans, Central Sulawesi, Indonesia. It lives on a special type of soft coral, can reach 18 mm in length and is beige colored with pink areas.
The other 5 species are free-living. H.comemani has been seen around seegrass. H. severnsi, pontohi and satomiae have been observed on seafans of different genera, colonial hydrozoans, algae (Halimeda) (2) or just anywhere moving around. They can often be found under slight overhangs under rocks.
Severn’s pygmy seahorse (Hippocampus severnsi)
This pygmy can reach a maximal size of 17 mm and is free-living. They are mostly brown with some red, orange and white bits.
Pontoh’s pygmy seahorse (Hippocampus pontohi)
The Pontoh’s seahorse is the one free-living species which is encountered by divers reasonably frequently. It is not known if this is due to higher abundance or if they are just easier to spot with their whitish color with some yellow or pink. They reach the same size as the Severn’s pygmies. When you find one there is most probably another one, or several, close by as they seem to live in pairs and groups.
The Pontohi seahorse is very similar to the Severn’s apart from the coloration. I did hear rumours that the H. severnsi and H. pontohi could be the same species.
Satomi’s pygmy seahorse (Hippocampus Satomiae)
This is the smallest seahorse with a maximum size of 14 mm. It is also hard to find as it only becomes active at dawn and congregates in small groups on small seafans during the night. It can be found in Borneo (Malaysia and Derawan) and northern Sulawesi (Lembeh strait). They are white/yellow in color with some orange markings.
Coleman’s pygmy seahorse (Hippocampus colemani)
So far this pygmy has been seen in Ryukyu Islands (Japan), Papua New Guinea and Lord Howe Island (NSW, Australia) which is the furthest south a pygmy seahorse has been observed. It can grow up to 27 mm and is yellow with white, red-rimmed blotches. (3)
Japanese pygmy seahorse or Japapigu (Hippocampus sp.)
This free-living species can be found from southern to central west of Japan. The Japapigu are characterised by a reticulated pattern on the body, the color can be brown, beige, pink and white.
Dive with the pygmy seahorses
Some of the best places to dive with pygmy seahorses are the Lembeh strait and Bunaken in North Sulawesi, as well as Raja Ampat and Wakatobi in Indonesia and Romblon, Philippines where it is possible to see several different species.