New publication: Finding fluorescent critters

Great news! I can finally share the reason why I was playing around with fluorescent torches for the last three years. The main biofluorescence paper I have been working on was published two weeks ago in the journal Conservation biology, happy days!

Previously I have written blog posts about funky biofluorescing fish, publications on frogfish that might be using fluorescence to attract prey, or just some funky fluo pictures to keep you you entertained. This particular story is about why I started working on biofluorescence in the first place and how the results of the research might help to protect little critters.

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Biofluorescent painted frogfish (Antennarius pictus)

As anyone who has ever tried to find small or camouflaged critters during a dive will be able to tell you, the little guys are pretty hard to find! This isn’t just a problem for a dive guide who wants to show pygmy seahorses or small frogfish to his divers, it is also a very real and well-known problem for marine biologists trying to study them. Finding these “cryptic” critters might be a headache for divers, but there is much more at stake when you are trying to collect data about critters that might be endangered with extinction.

If you are trying to figure out if an animal is endangered, the obvious first thing you want to know is “how many of them are out there?”. All good and well when you are studying elephants or giraffes, but slightly more tricky when you’re studying pygmy seahorses or a tiny goby that’s less than 3cm long! Not finding any pygmy seahorses or gobies could just mean that you didn’t look hard enough.


Biofluorescent moray eel (Gymnothorax zonipectis)

Scientists have three different ways of coping with this issue:

  • First option: Ignoring the problem by not counting small, cryptic animals when doing surveys. After all, if you weren’t looking it’s only normal you didn’t find any.
  • Second option: Adapting standard “visual surveys”. Usually by going slower or looking harder at a smaller area than when looking for big fish. This way you find more cryptic critters, but a lot still depends on how good a researcher is at spotting small fish.
  • Third option: (you might not like this one) Using chemicals that either stun or kill all the fish in a small area, after which all the fish are collected and counted. This method is very efficient and gives a good idea of which fish were living in that area. Unfortunately using methods that kill fish are not ideal, especially when you might be dealing with rare species.
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Two fluorescent seahorses (Hippocampus subelongatus)

This is where biofluorescence could come in to help. If you are confused about what biofluorescence is, definitely check out this post or this website. But briefly, biofluorescence happens when fish first absorb light and then reflect it in a different colour. Importantly, biofluorescence is  not the same as bioluminescence, where animals produce their own light.

So what has biofluorescence to do with finding cryptic fishes? A few years ago, a paper was published that stated that biofluorescence is common in camouflaged fishes. The work looked into evolutionary history, but the main idea triggered a little light bulb. I had previously seen coral researchers use biofluorescence to find baby corals (which are tiny, transparent, and VERY hard to see), so I wondered if the same technique could be used on cryptic fish.


The same bandtail scorpionfish (Scorpaenopsis neglecta), with and without fluorescence

So I decided to test it as a part of my PhD. I was very lucky to get support from multiple divecentres which helped me to go fluo-diving all across Indonesia and the Philippines. In the last 3 years I did over 200 dives observing, investigating, counting, and cursing fluo-and non-fluorescent fish. The results are published here, but the answer is: Yes, you can use biofluorescence to count cryptic fishes.

The vast majority (87%) of cryptic fishes I tested showed biofluorescence, compared to a small fraction (9%) of the non-cryptic fishes. A cryptic fish is 70.9 times more likely to be biofluorescent than a non-cryptic one! When comparing normal surveys with fluorescence surveys, I found three times as many triplefins (a small cryptic fish species) when using fluo surveys than during comparable normal surveys.

What was also really exciting (to me at least) is that I discovered that pygmy seahorses are fluorescent as well! Using fluorescence I found twice as many Bargibant’s pygmy seahorses than without the fluo torch. As if they weren’t cute enough already, these little guys are fluo pink when you look at them with the right tools!

Fluorescing seahorses are not the only reason why I am excited about this new publication…although it probably plays a bigger role than it should in order to call myself a serious scientist 😉 The great thing is that this is an easy and cheap technique that could help researchers study and conserve small fishes more efficiently than before. And in the end, that’s what it’s all about for me, making sure the oceans remain an amazing place full of critters to enjoy looking at…

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Robust ghostpipefish (Solenostomus cyanopterus) are biofluorescent too!


Fluo time

If this isn’t the first time you’ve read this blog, you probably know I am interested in the phenomenon of biofluorescence. I’ve previously talked written about what it is and what it might be used for. In the near future I’ll be tell you all about the details what I was actually doing. But I realized I haven’t shared any pictures recently that show just how beautiful and otherworldly it can be. So here is a random selection of fluo shots I took over the last two years. Enjoy!


A bubble snail (Hydatina physis) photographed in Lembeh Strait, Indonesia



Thorny seahorse (Hippocampus histrix) in Bima Bay, Indonesia



West Australian Seahorse (Hippocampus subelongatus) in Perth, Australia



Amazing coral in Raja Ampat, Indonesia



Reptilian Snake Eel (Brachysomophis henshawi) in Amed, Indonesia



Lizardfish (Synodus sp.) in Lembeh Strait, Indonesia



Cockatoo Waspfish (Ablabys sp.) in Lembeh Strait, Indonesia



Sea spider (Pycnogonid sp.) in Tulamben, Indonesia



Painted frogfish (Antennarius pictus) in Lembeh Strait, Indonesia



Juvenile Painted frogfish (Antennarius pictus) in Dauin, Philippines)



Barred moray (Echidna polyzona) in Nusa Kode, Indonesia


Training Marine Biologists: Coral Bay fieldtrip

Last week I’ve had the pleasure of exploring a new, beautiful area of Western Australia: Coral Bay in the Ningaloo Marine Park. I wasn’t visiting just for fun, but went over to tutor during a marine field project for the third year marine science students of Curtin University.  The goal of the course is to get marine science students hands-on experience with working in the field. To achieve this, the students worked in groups of 4 on a research project of their choice, with a bit of help from their lecturers (and tutors). As I have written earlier, there are a few very good and a few very bad reasons to want to become a marine biologist. This link is another great write-up for people considering to become a marine biologist. So besides being very keen to help with training a new generation of marine scientists, I was also rather curious to find out more about these people keen to trade civilised comfort for sunburns, sandy beds and soaking in salt water for hours on end.


Coral Bay

The 23 students taking the course were a diverse bunch, but they all share a passion for the ocean. To my great relief, most of them actually seemed interested in science and real marine ecosystems, and not just in hugging dolphins (=the WORST reason for anyone to consider becoming a marine biologist). Or maybe they just didn’t dare to admit it in front of me? Regardless of what motivated them, before I even got on the bus with them for the long drive (15 hours) to Coral Bay, they had already spent a few weeks preparing their research projects. The projects were diverse, with groups looking at topics like coral cover, parrotfish abundance, sediments, fish diversity, etc. None of the groups was looking at my kind of critters, but that only meant I would get to learn a few new things myself as well.


Student ready to survey fish

After arriving late at night in Coral Bay, the daily schedule was for students to go out to do fieldwork by day, and to come back to the research station in the afternoon to enter their data and analyse videos where possible. The tutors (Ash and me) were mostly expected to chill out on the beach to make sure nobody drowned, join students in the water to help where possible and answer any practical questions the students might have. As is usually the case with fieldwork, especially when you are new to it, getting started isn’t always easy. Regardless of what you are surveying in the ocean, you will need a fair bit of equipment, ranging from slates, to GPS’s, measuring tapes, plastic bags, cameras, quadrats, etc. Understandably, one of the main issues in the first days was forgetting to bring crucial pieces of equipment to the site, or loosing equally  crucial equipment in the water (sometimes never to be found again). Identifying fish and corals is also more challenging once you are in the water than what you’d imagine it to be while preparing your project. But as the week went on, the groups started to find their rhythm, got more confident and grew enthusiastic about getting results. That feeling of collecting real data is always a great one. The next step for the students now they’re back in Perth is to analyse their data and write their results up into a research paper. Which makes this project a great practice for other, more serious research projects they might do in the future.


Nikki staining corals

While the students were working away on their projects, I was also helping out my colleague tutor and PhD-candidate Ash. Her work looks at the effects of climate change, and as part of her research she will be collecting environmental data from all around Western Australia. This week she was testing her brand new, high-tech in-situ CO2 sensor. I imagined it would be as easy as chucking out an anchor in the ocean, but turns out it involves a fair bit more thinking and crafty tinkering to deploy the unit successfully. I also gave Nikki (the unit coordinator) a hand staining corals, a technique that is used to measure growth rates of coral. I had hardly done any work with corals before, so it was great to learn something new and see how coral scientists spend their days in the field.

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Biofluorescing Lizardfish

I even had time to go for a cheeky night-snorkel for myself to check out biofluorescence in the bay. Turns out there is quite a lot going on! Mostly coral showing green fluorescence, which seemed brighter than many locations I’d checked fluorescence previously. In the shallow, sandy areas there were loads of lizardfish and goatfish, and even a few bright green nudibranchs. It was interesting that during the snorkel I didn’t see any other fluo colours than green, compared to the mix of green, yellow, orange and red I got used to seeing in Southeast Asia. The question of why this is the case remains a mystery to me…

Looking back at this week, I am very happy I got the chance to join the field trip. From a personal point of view I got some great experience teaching and guiding students,  I learned a few new research methods in the water, all of that while staying in a gorgeous location. Most of all though, I enjoyed helping out with the education of new marine scientists. It is great to see motivated students find their way in the field and grow confident and enthusiastic about the work they are doing, and I am honoured to be able to help out with it. I don’t know which direction they will go after graduating, but it would be good to see at least a few of them as colleagues in the future. I wish them all the best, and hope they enjoyed the trip as much as I did.


New publication: Fluo frogfish lures

After a weekend looking for vagrant fish in the cold waters of Shark Bay (more about that later this week), I came home to find a pleasant email in my inbox. A new publication has been published online last week. This one is in the journal “Coral Reefs” and is about biofluorescence in the Striated Frogfish (Antennarius striatus), more commonly known as the Hairy Frogfish. The article can be found here, but is restricted access. For those of you who cannot access it, here is what it is about.


Hairy Frogfish by day. Photo: Luke Gordon


As I have written previously, I have been doing a fair bit of work looking at biofluorescence in fishes. During these surveys i had noticed something strange going on with the Hairy Frogfish: their bodies are not fluorescent, but their lure is (very strongly). As you might know, frogfish use their lure as a fishing rod, attracting small fish closer, which are then eaten whole. The fact that the Hairy Frogfish’s lure alone is fluorescent but their bodies are not, hints at the possibility that this fluorescence could be used in what is called “aggressive mimicry”. Aggressive mimicry is the term used for animals who pretend to be something harmless (the “model”) and use that to get close enough to eat their prey.


Hairy Frogfish (Antennarius striatus) with fluorescent orange lure

But the question was, what would it be trying to mimic? Are there animals out there that resemble this fluorescent lure? Cue my last Philippines trip. During a nightdive with the unparalleled science hobbit, we found three more Hairy Frogfish (with fluo orange lures). More importantly, we also found a lot of freeswimming worms near them. Most of them a similar size as the lure of the frogfish, AND the same colour fluorescence as those lures. The resemblance between the lures and the worms went further than just size, shape and movement, but also the fluorescence is imitated. We found our model species!


Fluorescent worm (top orange squiggle) and fluorescent lure (bottom orange squiggle)

This is very exciting, as it is the first time anyone found strong indications that biofluorescence might be used to help fish catch prey. To prove whether it is really used to hunt, lab experiments or extensive observations would need to be done to check if this fluorescence really makes a difference. So while this is a very exciting glimpse into an unexplored part of hunting strategies in the ocean, much more work needs to be done to understand all the details.

If you can’t access the article but want to read it, or you just want to know more, send me an email or ask in comments and I can send the publication to you.