The discovery of the Sodwana seahorse (Hippocampus nalu), Africa’s first pygmy seahorse

I am beyond excited to share the news that with a fantastic team of colleagues, we described a new species of pygmy seahorse!!! Hippocampus nalu, or the Sodwana pygmy seahorse in normal language, is the 45th seahorse species to be described, and the first pygmy seahorse species found in African coastal waters. It’s gorgeous and cute and very tiny.

To explain the story of how such a discovery happens, we wrote an explainer in The Conversation. Just so you wouldn’t have to do effort of clicking the link, I am also sharing the article below, which was co-written by myself, Louw Claassens, Graham Short, and David Harasti. All pictures provided are by Richard Smith.


Before you read this article, pause for a moment and look at the nail on your little finger. That’s about the size of a new species of seahorse discovered in the waters of Sodwana Bay, South Africa, which falls within the iSimangaliso Wetland Park, a World Heritage Site, in KwaZulu-Natal province.

Hippocampus nalu grows to a maximum size of just 2cm. It is the first pygmy seahorse ever discovered in African waters. Our team has conclusively demonstrated that Hippocampus nalu is physically and genetically distinct from the seven known species of pygmy seahorses. Its nearest relatives are found more than 8,000 km away in the Pacific Ocean.

Hippocampus nalu - South African pygmy seahorse, Sodwana Bay

An adult male Sodwana seahorse (Hippocampus nalu). Credit: 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.

The most astonishing part of this discovery is that it didn’t start in a laboratory, or with keen scientific minds assessing the likelihood of finding a pygmy seahorse in African waters. Instead, it began with a photograph.

Tracking the seahorse

Dr Louw Claassens and Dr Dave Harasti arrived in Sodwana in early 2018 looking for an entirely different animal: a seahorse-like species called a pygmy pipehorse. But then a local dive guide named Savannah Olivier showed them a photograph of a very small seahorse. The scientists recognised it as a pygmy seahorse, which are supposed to live an entire ocean away. South Africa is home to four other seahorse species, but this was the first time a pygmy seahorse had been observed in South Africa, let alone Africa.

Nine months later Louw returned to Sodwana Bay, this time accompanied by Dr Richard Smith, a pygmy seahorse expert. They, with 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.

Later they even found a tiny juvenile measuring just a centimetre in length, which was dwarfed by a diver’s finger.

Juvenile Hippocampus nalu - South African pygmy seahorse, Sodwan

Juvenile Hippocampus nalu – South African pygmy seahorse, Sodwana Bay. Credit: Richard Smith

Finding the seahorses was only the first step in describing the new species. The rest of the team now got to work. Graham Short, a researcher at the Australian Museum and California Academy of Sciences, compared the mystery seahorses with other pygmy seahorse species by looking at their characteristics under a microscope, as well as a powerful CT scanner. Dr Mike Stat, a geneticist from Australia, used genetic methods to test how distinct it was from other species. Through combined team efforts, we confirmed that the Sodwana pygmy seahorse was a new species and could give it an official scientific name.

CT_Hippocampus_nalu

CT scan of the Sodwana seahorse (Hippocampus nalu). Credit: Graham Short

The 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.

More to learn

The discovery of the Sodwana pygmy seahorse is exciting for more than just its scientific value. It provides new insights into the global distribution of these tiny fish and paves the way for further exploration in other locations. Only a handful of research publications focused on the ecology of pygmy seahorses exist, so anything we can learn more about these critters will help the future conservation of this unique group.

Finding a species like Hippocampus nalu also shows how little we know about Africa’s marine biodiversity, and how much more is left to discover. It highlights how important the observations of keen amateurs are to help scientists. If a keen fisherman did not consider a strange looking fish caught off the south coast of South Africa worth sharing with Marjory Courtney-Latimer in 1938, the discovery of the coelacanth, a living fossil, might never have happened.

Similarly, without a diver’s sharp eyes and an expert’s initial questions, the world would still not know that the Sodwana pygmy seahorse exists. As scientists, being open to questions from the general public not only helps inform non-scientists, but can also help us make new discoveries.

Hippocampus nalu - South African pygmy seahorse, Sodwana Bay

 A female Hippocampus nalu. Credit: Richard Smith

Time for something new

I never liked going to school. Not as a kid, not as a teenager, and not even as a young adult. Maybe I just disliked being bored so often? Even in the classes I was interested in, I felt that just absorbing all the knowledge in world was not exciting. My impression was that science already knew everything and that new discoveries were pretty much impossible. That science had somehow “stopped”.

Well, let me tell you one thing, it most definitely has not! I was not learning “all the knowledge in the world”, in fact LOTS of new things are discovered all the time! Since this blog is about ocean critters, let’s look at some of the critters that have recently been discovered. In the last year alone, new seahorses, frogfishes, gobies, jawfishes, and many other species have been discovered. So if you thought you’d seen it all, think again 😉

Seahorses and relatives

A new species of pygmy seahorse was described 3 months ago by Graham Short and colleagues. This ridiculously cute little seahorse lives in Japan and is called Hippocampus japapigu (=Japanese pig seahorse). These little wonders are less than 2cm in size and have a wonderful honeycomb colour pattern. Unlike some other pygmy seahorses, the Japanese pygmy seahorse does not live in seafans, instead it can be found in hydroids, algae, or soft corals.

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The newly describe Japanese pygmy seahorse (Hippocampus japapigu). Photo: Richard Smith

Even more recently, less than a month ago, another new pygmy seahorse species was discovered in South Africa. The first ever pygmy seahorse in South Africa! Dive operators in the Sodwana Bay region had found this small seahorse and asked pygmy seahorse expert Richard Smith about it. Together with IUCN seahorse expert Louw Claassens he went for an expedition and has confirmed the new species. It has not got a name just yet, but should be officially described sometime next year.

During the same expedition, Richard and Louw also found a new species of pygmy pipehorse! You might have never heard of pipehorses, but they are just fantastic. Sort of like a seahorse that disguised itself as a pipefish, or maybe the other way around?

SA pipehorse

A newly discovered, still unnamed pygmy pipehorse from South Africa. Photo: Richard Smith

Frogfish

Big news from Australia as well! A new frogfish species was described in the journal Copeia this week. The Narungga frogfish (Histiophryne narungga) is found in South and West Australia, and was named after the indigenous people living in the area. The beautiful new frogfish lives mostly in shallow water, where it does what frogfishes does best: mimicking sponges or other benthic organisms, hoping to catch unsuspecting prey that swims by. This small (less than 10cm), new frogfish is very much on my “critters to see before I leave Australia”-wish list!

H narungga

Narungga frogfish (Histiophryne narungga): A new Australian frogfish species. Photo: Rudie Kuiter

The researchers describing the Narungga frogfish, Rachel Arnold and Theodore Pietsch, are pretty much the rock stars of the frogfish world. Together they have described 9 new frogfish species in the last 10 years, the most famous of which is the Psychedelic frogfish!

Gobies

I’ll be honest, for someone who studies cryptobenthic fishes, I don’t know nearly enough about gobies. Luckily, other researcher do know a lot about gobies and they seem to be good at finding new species as well. This year a new species was discovered from the west Pacific Ocean. The polkadot dwarf goby (Eviota maculosa) lives in Indonesia, Australia and Pohnpei. Its small size, less than 2cm, probably explains why it has taken researchers so long to realise this was an undescribed species.

Eviota maculosa

Eviota maculosa, a new goby species from the west Pacific. Photo Mark Erdmann

Jawfishes

If you are not a keen muck diver or underwater photographer, you can be forgiven for not knowing about jawfishes. These cryptic fish live in holes in the sand and don’t venture out very often. Most notably, they are “mouthbrooders“, fish that hatch their eggs in their mouths. This week, two new jawfishes were described from Brazil. Thiony’s jawfish (Opistognathus thionyi) and the Brazilian dusky jawfish (Opistognathus vicinus) both seem to be endemic to Brazil, meaning they do not occur anywhere else. Thiony’s jawfish seems to live deeper than the Brazilian dusky jawfish, but otherwise, not much else is known about these new species.

O thionyi

Thiony’s jawfish (Opistognathus thionyi) from Brazil. Photo: Raphael M. Macieira

O vicinus

Brazilian dusky jawfish (Opistognathus vicinus) from Brazil. Photo: Raphael M. Macieira

This list of new critters is by no means complete. Many more species have been recently discovered, and many more will be discovered in the future. I find it very exciting that science isn’t ready yet and that there is so much more of the amazing natural world left to discover. If that doesn’t make you want to become a scientist, I don’t know what will… (We often have cookies in the office if that’s more your thing?)