Blue Zoo: Pygmy Seahorse

Featuring one amazing marine animal per week.

As their name suggests, pygmy seahorses are a group of remarkably small critters, generally maxing out around 2 cm (0.8 inches) long.

In addition to being small, many species of pygmy seahorse also have amazing camouflage. Because of this, they remained undiscovered until recently. The first species of pygmy seahorse ever discovered was the Bargibanti pygmy seahorse (Hippocampus bargibanti) in 1969. It was only when scientists took the gorgonian sea fan on which it lived into a lab for examination that the critter was found.

A pair of Bargibanti pygmy seahorses. Photo by Steve Childs via Wikimedia Commons, Creative Commons License. 

The Bargibanti pygmy seahorse reaches 2.4cm (1 inch) in length. It is found almost exclusively on gorgonians of the genus Muricella. The seahorse’s skin color matches its host gorgonian perfectly, which is usually soft pink or yellow. The knobs on its skin – called tubercles – help it blend in with the texture of the branches.

Denise's pygmy seahorse. Photo by Jenny Huang via Wikimedia Commons, Creative Commons License. 

There are now quite a few other known species of pygmy seahorses. For example, Denise’s pygmy seahorse (Hippocampus denise) rarely grows to be bigger than 1.6cm (0.6 inches). It lives on a wider range of gorgonian species. When the host retracts its polyps, the seahorse can also retract its tubercles to maintain its perfect illusion. This species wasn’t discovered until 2003.

Pontoh's pygmy seahorses. Photo by Silke Baron via flickr, Creative Commons License. 

Meanwhile, Pontoh’s pygmy seahorse (Hippocampus pontohi)  is usually less brightly colored. It tends to be white or brown colored, and its tubercles are smaller and fewer. It also doesn’t exclusively live on sea fans, and can be found on algae, hydroids, and bryozoans, as well.

A yellow Bargibanti pygmy seahorse. Photo by Steve Childs via flickr, Creative Commons License. 

Together with the other seahorses and pipefishes (but not the ghost pipefish!), they make up the Sygnathidae family. However, unlike other seahorses, which are famous for having males carry the eggs, in pygmy seahorses, the embryos develop in the female. The pygmies are all classified as members of the genus Hippocampus, along with the rest of the seahorse species, but eventually, it is possible that pygmy seahorses may be reclassified in their own genus. 

Primary source:  Allen, G.R. and Erdmann, M.V. 2012. Reef fishes of the East Indies. Volumes I. Tropical Reef Research, Perth, Australia. Pages 185-202.

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