Satomi's pygmy seahorse (Hippocampus satomiae)
|Size||Length: 13.4 - 13.8 mm (2)|
Height: 11.2 - 11.5 mm (2)
- Satomi’s pygmy seahorse is potentially the world’s smallest seahorse, and is hardly more than the size of a penny.
- The offspring of Satomi’s pygmy seahorse are each about the size of an apostrophe written in font size 12.
- As in all seahorse species, it is the male Satomi’s pygmy seahorse that becomes ‘pregnant’, carrying the eggs in a brooding area on the body.
- Satomi’s pygmy seahorse is named after the dive guide who collected the first specimens, Miss Satomi Onishi.
Satomi’s pygmy seahorse is classified as Data Deficient (DD) on the IUCN Red List (1), and all Hippocampus species are listed on Appendix II of CITES (1) (3).
The diminutive Satomi’s pygmy seahorse (Hippocampus satomiae) is believed to be one of the world’s tiniest seahorses (4). Either transparent-grey or pale whitish-brown, this tiny seahorse has red blotches on the operculum, body and tail, and the tail also has brown banding (2). The top of the head is darker than the remainder of the body, and each eye is surrounded by a black ring and has a dark spot in front. Spines all over the body give Satomi’s pygmy seahorse an uneven appearance. The most obvious of the spines are the large double pair above each eye and an angular one on the nose (2).
The brooding area on Satomi’s pygmy seahorse is located on the male’s body, in front of the anus. Newborn individuals are only three millimetres in height and are entirely jet black (2).
Satomi’s pygmy seahorse is known to be present at several sites within Indonesia, such as Derawan Island, and Lambeh in northern Sulawesi. This species is also known from northern Borneo (2).
A marine species, Satomi’s pygmy seahorse has been observed on a variety of soft sea fan corals, and in proximity to aquatic invertebrates such as colonial hydrozoans and bryozoans. This seahorse species has also been found among coralline algae, hard corals such as Fungia species, and in rock crevices (2).
Satomi’s pygmy seahorses gather at night to rest in groups of three to five individuals. These groups converge on small sea fans at depths of 15 to 20 metres, below overhanging reefs. This species becomes active again at dawn, but is highly elusive during the daytime (2).
As in other seahorses, the male Satomi’s pygmy seahorse has a brooding pouch where the female deposits eggs and the male then fertilises and incubates them. One of the male specimens collected was carrying around eight eggs in the brooding area (2).
It appears that the physical characteristics of Satomi’s pygmy seahorse provide effective camouflage against its habitat, protecting it from potential predators (2).
There is currently no data available on the diet of Satomi’s pygmy seahorse. However, in general seahorses feed opportunistically, sucking nearby invertebrate prey swiftly from the water through their tube-like snout (5).
There are no known threats to Satomi’s pygmy seahorse at present.
No specific conservation measures are currently known to be in place for Satomi’s pygmy seahorse. However, all members of the Hippocampus genus are listed under Appendix II of the Convention on International Trade in Endangered Species (CITES), and therefore trade in this species should be carefully controlled and monitored (1) (3).
Find out more about Satomi’s pygmy seahorse:
FishBase - Hippocampus satomiae:
More about seahorses and their conservation:
BBC Nature - Seahorses and pipefish:
The Seahorse Trust:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
- Bryozoa: a group of sedentary aquatic invertebrates that typically live in colonies of interconnected individuals. These colonies have a mossy appearance, giving bryozoans the name ‘moss animals’. Most bryozoans use tentacles to filter small food particles out of the water.
- Coralline algae: red algae (a type of simple plant without roots, stems or leaves) in the family Corallinaceae. These algae are hard due to deposits of chalky calcium carbonate within the cell walls, and are usually coloured pink, purple or red.
- Fertilisation: the fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Gestation: the state of being pregnant; the period from conception to birth.
- Hydrozoa: a group of aquatic invertebrates that includes hydras and jellyfishes. Many hydrozoans are colonial, and in some species the life cycle alternates between a free-swimming reproductive form and a solitary or colonial sedentary form.
- Incubate: to keep eggs warm so that development is possible.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- Operculum: in fish, a hard, bony flap that covers and protects the gills.
- Sea fan: a type of coral that grows from a point of attachment and has a tree- or fan-like skeleton. Sea fans are mainly found in warmer seas.
IUCN Red List (January, 2013)
- Lourie, S. and Kuiter, R. (2008) Three new pygmy seahorse species from Indonesia (Teleostei: Syngnathidae: Hippocampus). Zootaxa, 1963: 54-68.
CITES (January, 2013)
Scales, H. (2010) Sea life photos: Five new pygmy seahorse species found. National Geographic News, 28 October. Available at:
Project Seahorse (January, 2013)