Tiny new seahorse species discovered

A juvenile pygmy seahorse
A juvenile pygmy seahorse | Image: Richard Smith

A rather mysterious new species of tiny seahorse has been discovered in waters off South Africa

The pygmy seahorse (Hippocampus nalu) is about the size of the nail on your little finger, growing to a maximum of just 2 cm. It’s the first pygmy seahorse ever discovered in African waters and is physically and genetically distinct from any other known species of pygmy seahorse. Strangest of all, its nearest relatives are to be found more than 8,000 km away in the Pacific Ocean.

It’s discovery began with a photograph. Two marine biologists arrived in South Africa in early 2018 looking for a species called a pygmy pipehorse. Sodwana falls within the iSimangaliso Wetland Park, a World Heritage Site, in KwaZulu-Natal province. A local dive guide there showed them a photograph of a very small seahorse and the scientists recognised it immediately as a species supposed to live an entire ocean away, the pygmy seahorse.

An adult male pygmy seahorse
An adult male pygmy seahorse | Image: Dr Richard Smith

Nine months later Dr Louw Claassens returned to Sodwana Bay, this time accompanied by Dr Richard Smith, a pygmy seahorse expert. They, together with the original dive guide Savannah Olivier, found a pair of the tiny pygmy seahorses along a rock face at about 15m depth.

The little creatures were grasping on to slivers of algae amid raging surging seas. The reefs of Sodwana Bay are exposed to the swells of the Indian Ocean, very unlike the more sheltered coral reef settings in the tropical Pacific where the other known pygmy seahorses are found.

An adult male pygmy seahorse
An adult male pygmy seahorse | Image: Dr Richard Smith

Seahorses are threatened all around the world. Many species are at risk of becoming extinct because of human activities such as bottom trawling, over-fishing, and habitat destruction. As a result, several species are listed on the IUCN Red List of Threatened Species. However, to date no pygmy seahorses are considered threatened – because we simply do not know enough about them. By discovering more species, and learning more about these tiny creatures, scientists can offer advice on how best to protect them.

Pygmy seahorses can also provide an important boost for tourism: scuba divers love these small species and are willing to travel far and wide for a chance to see them. If coastal communities and scuba divers alike are taught about the best ways to protect these species and others in the oceans, there can be huge economic and social benefits.

Ocean Desk Top Ten (title graphic)

10 facts about pygmy seahorses…

1. Until this discovery, all but one of the seven species of pygmy seahorse were all found in southeast Asia

2. Pygmies range in size from 1.4 – 2.7cm, from the snout to the tip of the tail – human finger nail to toe nail in size

3. Like other seahorses, it’s the male pygmy that becomes pregnant. He gives birth to around a dozen young after a gestation of 10-14 days

4. Pygmy seahorses feed on tiny crustaceans that share their local habitat

5. Some pygmy seahorses are found on seafans usually more than 10m below the surface

Denise’s pygmy seahorse on a sea fan
Denise’s pygmy seahorse on a sea fan

6. They have among the smallest home range of any fish, not venturing further than an area the size of a side plate for all their day-to-day activities

7. Pygmy seahorses differ morphologically from all other seahorses, possessing a single rather than paired gill openings in addition to a brood pouch located on the trunk, rather than the tail

8. They don’t have eyelids and are sensitive to light (photographers please note!)

9. Confusingly, there are a couple of tiny seahorses which aren’t true pygmies and generally referred to as ‘dwarf’ seahorses, these include the Debelius and Minotaur species

10. The Sodwana pygmy seahorse name “nalu” has three layers of meaning: In the local isiXhosa and isiZulu languages it means “here it is”, to show that the species had been there all along until its discovery. “Nalu” is also the diver Savannah Olivier’s middle name. Finally, “nalu” means “surging surf, wave” in Hawaiian, which hints at the habitat the species lives in.


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