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.

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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.

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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

Finding the Knysna Seahorse: Mini-blog 6

I feel like I only just arrived in South Africa to look for endangered seahorses, but instead I am flying to Johannesburg where I will catch a connecting flight to Perth. This trip was no different than other fieldwork trips in that regard: what looks like a long time of sampling at the planning stage just flies by before you know it.

Louw and me have been busy since the last mini-blog. Most importantly, we successfully finished sampling! The last locations were less explored areas than the first ones, which is very exciting. Even if we do not find seahorses in these spots, they give inspiration to come back for new research projects.

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Cormorant in Jongensfontein

After wrapping up the sampling we visited Stellenbosch University. The university is the home to the von der Heyden Lab, which specialises on genetic research for conservation and biodiversity planning. They also have an eDNA project which investigates fish diversity in South Africa. During our visit I gave a talk about my own research to the marine students in the university. It was great to share my love for strange critters, especially since the students had some very relevant questions at the end of the talk. As much as I enjoy talking (or writing) about my research, it’s even more fun to have a conversation about it and getting a fresh look through someone else’s eyes.

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South African penguins (Spheniscus demersus) taking a stroll

In the last two days of the trip we relaxed, caught up with friends, and explored Cape Town and False Bay. The highlights were definitely diving in the kelp forests of Simonstown and visiting the nearby African penguin (Spheniscus demersus) colony. While I have dived in cold water before, I never had the pleasure of seeing this particular ecosystem. If you ever have the opportunity, I can highly recommend it!

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Kelp diving

If a coral reef dive is like swimming through an underwater flower garden, kelp diving would be the equivalent of walking through a forest. There’s something very special about weaving your way through underwater plants that reach from he bottom all the way to the surface. The sunlight is filtered and the canopy above creates shadows you just do not get in other kinds of diving. On top of that, the bottom is very rich with all kinds of life. There are plenty of invertebrates like sea urchins, featherstars and nudibranchs. The fish life is very different than what I am used to, the small pufadder shysharks (Haploblepharus edwardsii) only live in South Africa area and are the cutest little things. To top it off, two southern right whales passe by close to shore as we were exiting the water. Louw even managed to snorkel out and catch a glimpse of them!

I guess it’s safe to say that this trip has been a successful one. It will be another few months before we will have all the results, but I am very excited to discover in which places we found the elusive Knysna seahorse!

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Not a bad spot for a dive…

 

Finding the Knysna Seahorse: Mini-blog 3

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Kleine Monde

Today was busy, so not enough time to properly write. Instead, to give you an idea of what I do all day,  here is the schedule of today’s fieldwork.

  • 6:00 – Wake up
  • 6:30 – Drive to first site (Kleine Monde)
  • 7:50 – Collect samples (Kleine Monde West, 2 locations)
  • 8:10 – Collect samples (Kleine Monde East, 2 locations)
  • 10:00 – Back at room, start filtering samples
  • 12:30 – Drive to site (Bushmans estuary)
  • 13:15 – Collect samples (Bushmans, 2 locations)
  • 14:50 – Back at room, start filtering samples
  • 19:30 – Realise samples contained more sediment than expected and that filtering will take twice as long as planned, eat food, drink some wine
  • 21:40 – Still filtering, drink tea, lots of tea
  • 23:25 – Finished filtering samples, time to clean up
  • 23:50 – Off to bed!
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Louw on her way to sample Bushmans estuary

 

Finding the Knysna Seahorse: Mini-blog 1

Yesterday I wrote about the exciting projects that are coming up, one of which looks at the Knysna Seahorse (Hippocampus capensis). The next two weeks I will be in the south of South Africa, where my friend Louw and I will to try to learn more about this endangered species. I promised I would try to give you frequent updates about what is going on, so here is the first of this fieldwork-mini-blog series.

I am extremely lucky that I get to travel to amazing places for my work, but sometimes the traveling alone is almost as much adventure as the actual work. Last night’s flight was late (not too much, just over an hour), but it meant that I’d struggle to make my connecting flight. It turned out there was no need to worry, since the domestic flight I was supposed to take had been cancelled altogether! Luckily I got a place on a different flight a few hours later (with “Mango Air”) which brought me to my final destination, George. In George I got picked up by Louw, and after a minor struggle to get all our equipment in the car, we drove off to the first fieldwork location, another 5 hour drive from the airport.

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Arrival in George, with the very orange plane of Mango Air

Which brings us to the reason why we are doing this project, the Knysna seahorse. This species is quite special, but not necessarily for the right reasons. It only occurs in a few estuaries in the very southern tip of South Africa, in the Knysna region. Since it is so isolated, and only occurs in so few places, any environmental impacts can have a big effect on the species. Because of this unique situation, the species is listed as “Endangered” in the IUCN Red List.

You might be wondering “That’s all fine, but what are you two going to do about it?”. The main goal of this project is to figure out exactly WHERE the seahorses live, and if there are places where they are present that might have been overlooked in the past. Finding (or just as important, NOT finding) these new places are important for managing this species. We will do this not by diving and looking for them, but by using a shiny new method called “Environmental DNA” (or “eDNA” for short).

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The eDNA mobile

I will explain what exactly eDNA is in a future blog, but we will basically be scooping up water and then filtering that water to find traces of seahorse DNA. These traces will tell us whether or not seahorses are present in the estuary we just visited. The benefit of this method is that there is no need to go in the water, where it is easy to miss camouflaged species like seahorses. It also avoids using other, more destructive methods, like using fish poison to find out what is around you.