Defining Nemo: A Deep Dive Into Taxonomy (With Kai The Fish Guy)

One of the defining moments of my childhood was a holiday around Australia in the back of a Holden Commodore. My parents drove my sister and me around the whole country, and right in the middle of the holiday we took a trip out to the Great Barrier Reef. Swimming among such a mind-blowing variety of fish species was an unforgettable experience, and one I was able to pass onto my own kid last year. We’d get back into the boat after a swim and stare at an ID card my wife had bought us, trying to figure out which of the cornucopia of dazzlingly-coloured species we had seen.


I’ve never been much of a taxonomist (to be fair every cyprinid looks exactly the same, don’t @ me), but the abilities of the people who can wade through the finer details of morphology, genetics and speciation to identify and classify any group of species, let alone one as rich and diversified as coral reef fish, astonishes me.

Which is why I called up Yi-Kai Tea in mid-September to pick his brain about taxonomy and the world of fish. Kai is a photographer, scientist and avid fish-keeper, who has described and named 12 different species of fish over the last four years. Currently completing his PhD at the University of Sydney, Kai is about to publish his first book, simply entitled ‘Fishes’.

Sam Perrin (SP): For people outside, taxonomy must seem easy. It’s just putting stuff in boxes right? But the more you learn about taxonomy, the messier it gets. Why is that?

Yi-Kai Tea (YKT): It’s a question with multiple parts. The first challenge is that it depends on what your concept of a species is, and everybody has a different species concept. There is no one-size-fits-all approach, there is no one species concept that is the answer to every biological problem. The most popular is the biological species concept, where species can only interbreed with each other and not with other species. But we know now that hybridisation is very common, it can even happen across genera.

The second challenge is that even with traditional taxonomy, where A and B are very clearly different species, it’s not just about sorting things and putting them into categories. A lot of taxonomic work builds upon previous taxonomic work, and in some groups – for example fungi, some groups of flies, some groups of fishes – there’s just been historically very scant literature. That makes it really hard to do work in the present. It means there’s a lot of missing parts to the puzzle you’re trying to put together.

SP: Does that make training new taxonomists difficult?

YKT: Well that’s the last big challenge – funding and training. Taxonomy is a ‘sunset industry’, there are not many new taxonomists being trained, because there’s no funding for training. Not many universities have a course in taxonomy where you can go and learn to be a taxonomist. And it’s such a niche field, that if you work on fishes you can’t apply the same skills to plants or insects, because every group of animal has its own set of very specific characteristics and classifications. So the skills needed to discern species within a certain group, you build those over your entire career, you never stop learning about them. Which is why it’s hard to pick up taxonomy, because there are not many people picking up and passing down this knowledge. 

It’s very exciting, it’s very rewarding, but it’s not a discipline that is well-celebrated, which is why we don’t have many permanent positions offered to taxonomists. Lots of taxonomists right now have started to branch out into things like phylogenomics, phylogenetics, and systematics. Many make themselves more marketable by packaging taxonomy into something that is more well-received and well-funded.

SP: You described a new fish in 2019 and named it after the Black Panther’s homeland – Cirrhilabrus wakanda. You’ve said before that you knew it was a missing piece of the puzzle, but how could you know there was a missing fish species in an area?

YKT: I do most of my research on fairy wrasses, I’ve described about 10% of all the fairy wrasses. And certain groups of fairy wrasses have a very predictable pattern when it comes to biology and distribution. And Wakanda belongs to a species complex which displays very telltale characteristics. This particular group has species which are distributed all around the world, and the species when put together form very nice little geographical ranges, which fit side by side like a jigsaw puzzle. But curiously there was a piece missing from the coast around South Africa, where you would expect to find one. All the major zones of the western Indian Ocean were filled up already, there was a species in Mauritius, the Maldives, the Red Sea. But then there was one missing hole in this puzzle. Based on the pattern, we inferred that there was something there.

So when Dr. Luiz Rocha (Assistant Curator of Fishes at the California Academy of Sciences) sent me a photo from fieldwork in Tanzania, I knew straight away that it was that missing species in that group. It was immediately identifiable based on its purple scales.

Cirrhilabrus wakanda, which Kai named in 2019 after the fictional home country of the Black Panther (Image Credit: Yi-Kai Tea, All Rights Reserved, Image Cropped)

SP: So it was a quite literal piece of the puzzle?

YKT: Yes it was very literal actually. We think that there’s another one in the Indian Ocean that hasn’t been discovered yet as well. There are a lot of new species out there, just waiting for people to go down deep enough and photograph them.

SP: What sort of process do you have to go through to name a species?

YKT: In order to publish a new species and have it recognised as a valid species, you need to fulfil certain criteria in accordance with ICZN, which is the International Commission on Zoological Nomenclature. Basically it has to fulfil certain criteria of their code. You have to prove that it’s new based on comparisons with other known species, make sure the name that you’re giving is available, and then publish it.

To publish a new species what I normally do is first make sure I have an adequate number of specimens to capture all the variation in morphology. If you’re a taxonomist that specialises in a certain group, you kind of have that instinct to know what it’s most closely related to. If you work on parrots you’re not going to compare a cockatoo with a pigeon. You do a comparison either based on colouration patterns, or morphology, or genetics, or a combination of all of them, and then you write a paper explaining why this is different, and then publish. So with Wakanda for example, I knew it was very closely related to several of the other species that lived also in the Indian ocean, based on a set of characteristics that no other species share. 

SP: You named a species after your mum (Chromis tingting). Was that a spur-of-the-moment thing, or had you planned that for a while?

YKT: I’ve always wanted to name something after my mum, but I didn’t really have the appropriate one to do it with. I’d worked on fishes that were not collected by me, or I’d collaborate with someone and didn’t always have creative control of the name. You have to have unanimous agreement with your other co-authors. It took me a while to get to a fish of which I had full control over the name. And then the first few times that happened I felt that my Mum’s name wasn’t appropriate for that species, like Wakanda for example. So it took a while, but eventually we got to one, it was a nice simple fish, it didn’t look ugly or anything. She thought it was a nice gesture.

SP: Have you made any controversial decisions over the last few years?

YKT: There is one species – Microcanthus joyceae – which I didn’t describe as new, instead I resurrected it from synonymy. If you describe something as a new species, down the line another taxonomist may come along and say “look I don’t agree with this, I don’t feel the justification for a new species is necessary”. It gets synonymised back into whatever it was before. So when I was doing my undergraduate, I worked on a population study of a fish that is found in Japan and Australia but nowhere in between. It’s this really interesting biogeographical phenomena that we call anti-equatorial. It’s found in opposite hemispheres, but not within the equator or the tropics. 

This disjunction has led to many species being described as different, even if they look identical. They’re found on separate hemispheres and not breeding, so why not call them different species? There’s very very little external morphology or coloration patterns separating them. And historically the two species I was working on had been given two different species names, but they’d been subsumed back into one – Microcanthus strigatus. So we had two populations which started as one, but they’d been separate for nearly two million years, and are no longer interbreeding. And I had to make a decision as to whether I should resurrect one of them as a separate species, which I did. I think to me, that’s the most contentious taxonomy I’ve done.

Chromis tingting, the Moonstone Chromis, which Kai named after his mother (Image Credit: Yi-Kai Tea, All Rights Reserved)

SP: Fishes have been a hobby of yours from very early on. What was the point when you realised that you wanted it to be more than just a hobby?

YKT: I’ve been involved in the marine aquarium industry for a very long time, I want to say more than 10 years now. I used to be a very avid fishkeeper, I used to go to the fish store every day. Photography was also a big passion of mine back then, I started tinkering with my brother’s hand-me-down camera, then I got one of my own. I started taking photos and keeping fishes. I also used to write for various magazines and blogs, and I would go to press shows and conferences as well. So that whole industry side of my life has been really really enriching, and put me in contact with a lot of people who straddle the divide between academic and industry. And I’ve been really interested in that juxtaposition of these two big bodies.

I’ve also had a really strong interest in fishes in general, and there are a lot of questions that I’ve always been asking. I owned a fish from the pet store that was an undescribed species, and I couldn’t understand why. And nobody would answer me, so I decided to figure it out myself. I started approaching some of these people when I was an undergraduate, showing that I knew a lot about fishes from an amateur perspective, but that I wanted to take it a step further. I eventually described that fish that I owned, Cirrhilabrus isoceles.

SP: How does a fish that you can find in a pet store go unnamed for so long?

YKT: That’s the question that was plaguing me for years. I was flipping through guidebooks and magazines and looking at photos online, and everything would be vague and maybe list it as a subspecies, or a species it might be related to. Even with really charismatic fishes like fairy wrasses, you can walk down the street and buy it from a fish store, put it in the tank, and the thing has no name. How can something so gorgeous that you can buy ten minutes away from your house be undescribed? What are people doing!? 

Now as a taxonomist I realise it’s not as easy as it seems, sometimes you don’t have the material. Just because it’s common in the aquarium industry doesn’t mean it’s common in the museums. That insatiable urge to want to learn more about these things pushed me into the field of taxonomy. There are lots of species out there which still suffer the same fate. You can see them in dive magazines or books, just waiting for someone to come and work on them.

SP: Marine fishes, and in particular coral reef fishes, get a lot of the public spotlight, compared to their more maligned freshwater cousins. What life advice would you give to freshwater fishes?

YKT: Do better.

Actually it’s something that I’ve always wondered. My brother is probably a bigger fish nut than I am, but he only works on freshwater fishes, he doesn’t do anything marine. And he’ll show me the most beautiful freshwater fish that he has and I’m like “mate this is not even close to what we have on the reef”. The colour is not as vibrant, it’s not as interesting. 

It just comes down to the fact that coral reefs are really really complex ecosystems. There’s so much going on down there. There’s so much sound and colour. So if you’re a fish that lives there, you’ve got to really stand out if you want to attract the attention of another member of your species, while not making yourself conspicuous to predators. So you get things like iridescent, ultraviolet, infrared colours, and they come together to make coral reef fishes a much more successful type of animal.

You can read more about Kai’s research at his website at this link, or follow him on Twitter @KaiTheFishGuy.

Sam Perrin is a freshwater ecologist currently completing his PhD at the Norwegian University of Science and Technology who thinks freshwater fish are doing just fine and don’t need any life advice from a bunch of flashy iridescent idiots thank you VERY much. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.

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