Guestblog: Frogblogging – insights in the world of frogfishes

IMG_0737This month’s guestblog is written by Daniel Geary, the resident marine biologist at Atmosphere Resort in Dauin, Philippines. It’s safe to say that Daniel is very passionate AND knowledgeable about frogfishes. He’s been studying them for years in Dauin and even wrote (and teaches) a PADI speciality course on these awesome critters! In this blog he gives a taste of some of the many ways frogfish are fantastic and deserve a closer look.


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Longlure frogfish (Antennarius multiocellatus) from Florida

Frogfish. You have probably heard of them, and if you’re a diver you might have seen one or two before. You have definitely swam right past a few of them without knowing they were there. Although most of them have a face only a mother could love, behind this outer layer exists a well-adapted, expert fisherman with amazing camouflage capabilities. They are more than just a lazy, camouflaged blob that sometimes doesn’t change location for a year.

Frogfish are anglerfish, although they are what I call a shallow, less ugly version of anglerfish. They have a rod and a lure that they actively fish with when necessary. Their fins look like limbs that somewhat resemble those of a frog. They must inhale water though their mouth to then push it out of their gills which aids in locomotion. Frogfish are experts at changing color and can change color multiple times, usually to blend in with their surroundings. Normally a full color change takes about 2 weeks, but frogfish have been witnessed to change color in under ten seconds when disturbed by divers’ bubbles and needing to switch to a different coral.

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The same giant frogfish (Antennarius commersoni) changing colour in two weeks

There are around 50 species of frogfish, with a new species or two being described every few years. Frogfish can be found worldwide in tropical and subtropical waters (but not in the Mediterranean). Some species are only found at a handful of dive sites, others are only found in one country or continent. A handful of species are found in the majority of the warm water areas, but only the Sargassumfish is found worldwide. There have been a few occasions where Sargassumfish were found all the way up in the cold waters of Norway and Rhode Island – way out of their preferred habitat, but they live their lives floating in seaweed and/or other debris and are at the mercy of the ocean currents.

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Sargassum frogfish (Histrio histrio) often wash up on the shore of the Atmosphere housereef, when they do, they get released back into deeper water

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Painted frogfish (Antennarius pictus) using its lure to attract prey

Frogfish are ambush predators which is why they seem to be so lazy. The less they move, the better predators they can become due to algae, coral polyps, and any other organisms that use the frogfish as habitat. I call this being lazily efficient, or efficiently lazy. Frogfish will make minimal adjustments to their body positioning before they begin to lure prey, although sometimes the frogfish are so camouflaged that they don’t need to actively attract prey. Frogfish swallow their prey whole by opening their mouth and creating an instant vacuum since the volume of the mouth increases up to twelve times the original amount. This means frogfish can swallow their prey whole in six milliseconds. They feed on a variety of organisms, depending on where the frogfish lives. Generally they like small fish like cardinalfish, shrimps and crabs, and sometimes other frogfish. They can comfortably swallow prey that is their own size, and with a bit of effort they can swallow prey up to twice their size, although this can result in the death of the frogfish if the prey item is too large and gets stuck in their throat. Frogfish do not have many predators, but they are sometimes preyed on by moray eels, triggerfish, and lizardfish. Flounder will sometimes suck up juveniles from the sand and fishermen in the Philippines have been known to capture and eat Giant Frogfish.

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This giant frogfish (Antennarius commersoni) bit of more than it could chew and did not live to tell the tale. Photo taken at Apo Island

 

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Frogfish egg raft

Frogfish have been known to eat each other if they get too close, especially after failed mating attempts. A male will approach a female when she is bloated with eggs. He will do his best to show off for her, which includes expanding his fins to their maximum sizes, rapidly opening and closing his mouth, as well as violently shaking his body. At this point, the female either accepts him or tries to eat him. If accepted, he gets to stand next to the female, which is the frogfish equivalent of holding hands. Once he is ready to mate, he will start again with his flashy moves, but this time bouncing around the female. Sometimes he has to physically swim her off the substrate to mate, other times she is able to swim on her own. Once they are a meter or two above the substrate, the female releases her egg raft, causing her to spin rapidly. The male then fertilizes this egg raft, also spinning rapidly. Both the frogfish then return to the bottom as the eggs float off into the distance. The eggs will hatch a few days later and become tiny planktonic frogfish babies, which will continue to float for a month or two until they are big enough to settle in the substrate, change color, and begin their lives as adorable frogfish.

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A male (red) painted frogfish (Antennarius pictus) trying to convince the female (yellow) to mate

Stay tuned for more frogfish insights coming in December, where I’ll write about the history of frogfish research and describe a handful of frogfish species, including a potentially “new” species. Until then, keep an eye for frogfish on all your dives, especially if you’re in warm water.

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Poll: alternative muck diving terms

voteAfter the recent blog about the history of muck diving I received some interesting suggestions about alternative names to describe the activity. Because this is a democratic blog, it’s time for a poll! Tell me (and the rest of the world) which name you prefer and who knows, it might just catch on!

While less talked about than the term “muck diving”, a few people suggested the world needs a fitting name for muck dive enthusiasts (maniacs?).  In bird watching the most fanatic bird watchers are called “twitchers“. I reckon finding an appropriate term for those divers that love nothing more than finding new critters could be interesting.

I have been offered some suggestions, but feel free to add others. For the sake of inspiration, the name “twitcher” actually stems from the nervous behaviour of a well-known bird watcher in the 50s and 60s. So feel free to make fun of your photograph happy critter-enthousiast dive buddies 😉

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Muck-enthusiast in action (can you see the black hairy frogfish?

What’s in a (species) name?

A recent publication about the family tree of manta and mobula rays got quite a lot of attention on my social media feeds, inspiring me to explore the topic a bit further. I’ll try to keep this blog as jargon-free as possible, but I apologise in advance if I occasionally veer off into technical terminology.

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Manta-selfie in younger days

Before I get going in earnest, a quick introduction to scientific names (or “binomial nomenclature“). Scientific names consists of two parts, the first part is the genus of the species (a bit like your surname), the second part the actual species name (like your first name). A few examples: Antennarius pictus, Homo sapiens, Wunderpus photogenicus. Names are usually in Latin or Greek, or anything that vaguely sounds like either one of those. Unlike common names, the scientific names for species are the same wherever you go in the world, which is helpful when talking to scientists who speak a different language than you do.

So what is the manta vs. mobula article all about? Manta rays are large, charismatic fish that grow up to 7m wide who look and feel a bit like stealth bombers when they glide over your head during a dive. Until recently, two species of manta rays were recognised: Oceanic manta rays (Manta birostris) and reef manta rays (Manta alfredi). Mobula rays look very similar to manta rays, but are smaller and differ from mantas in a few other ways. The newly published paper did genetic research to see just how closely mantas and mobulas are related, and they turn out to be a lot closer related than we previously thought. To put it into human perspective, as a species manta rays were thought to be something like a cousin to mobulas, but they turn out to be more like a brother/sister. In biology-slang: manta rays are now seen as belonging to the same genus as mobula rays. Which in turns means that their scientific name changes from Manta to Mobula, so Mobula birostris and Mobula alfredi. A bit like an adopted child getting a new last name.

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Reef manta rays (Mobula alfredi) – Photo by Luke Gordon

What the article does NOT claim, is that manta rays are now suddenly a different species. It just means they are classified differently by taxonomists (and that they might get more invitations to Mobula social events). The common names will remain the same, manta ray species do not suddenly disappear or behave differently. It will take a while before ID guides will pick up on the name change and a lot longer (if ever) before the majority of ocean enthusiasts will notice.

A good point made by a friend, is that a different scientific name means certain official documents concerning the trade in protected species might have to be adjusted. Luckily the statute of manta rays as a species is not questioned, so existing conservation laws should not need to be changed.

But how does this happen? Why do scientists decide that a species has a different family tree than we’ve always thought? This is actually not an uncommon event, in the last years many species (including nudibranchs and frogfishes) received different names and classifications. One reason is that science is constantly evolving and as we learn more, we update our knowledge and correct mistakes from the past (or make new mistakes which might in turn be corrected later). In the manta/mobula-case: by using modern methods we found out that the family-relations were different than we assumed from only looking at the anatomy of these animals.

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Manta ray (Mobula alfredi) making its stealth bomber-like approach

Another (more surprising) reason, is that we still don’t have a good definition of what a species is. Human nature impels us to order the world around us into categories with different names, initially very broad (animal / plant / rock), then more detailed (fish / mammal / bird), more detailed still (ray / shark / frogfish), until you reach the scientific naming system (Mobula birostris / Mobula alfredi / Mobula mobular). But sometimes it is difficult to decide where one species stops and another one ends.

I know that at school you get taught that two species are different when they can’t produce fertile offspring (Horse + Donkey = Mule, but mules are infertile, so horses and donkeys are different species). To a large extent this definition works, but it breaks down when you start looking closer, especially when you look in the ocean. The question on how to define a species is a surprisingly hot topic in biology! I will explore the species-definition problem in a different blog later (promise!), but it would make this one a bit too long.

In the meantime, you can call manta rays Mantas, Devil rays, Big-ass mobulas, or anything else that floats your boat. As long as you have a great time watching them and try to protect the environment they live in I’m happy!

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Does it really matter what these beautiful animals are called? Photo by Luke Gordon

Growing up

Growing up isn’t always easy, going from the playful life of a child to become a (seemingly) functional adult takes blood, sweat and tears. Anyone reading this blog who longingly remembers the awkward changes your body goes through puberty, please feel free to share in comments below whether it was the pimples, the voice changes, gangly limbs or any other similar affliction you’d like to get back in your life. I am fairly confident the comment section won’t be overly populated. If you think growing up was hard for you or any other human, take some time to consider how much more extreme becoming an adult is for fish.

As you or may not know, most fish start their life as transparent larvae, floating through the blue. Once they are large enough to become proper fish, they “settle” on the reef. This settling is the first big growing up fish have to do.  Forget about years to grow from a baby into a teenager. Typically within less than 2 days, the freshly arrived larvae change colour and massively grow in size. If you think changing colour and doubling in size within a month isn’t hard enough as a childhood, consider the following. Over 50% of baby fish arriving on the reef get eaten within the first two days of arriving on the reef! Talk about a bad first day at school…

Childhood might be the most dangerous time for fish, but that doesn’t mean puberty is any easier. While we humans complain about acne and high pitched voices, fish have got other things to cope with. Many fish change colour again as they become adults, which is a minor nuisance compared to the fact that some radically change shape. Good examples are batfishes, which start by looking like leaves or flatworms to then turn into a relatively boring plate-looking fish.

Shapeshifting is peanuts compared to a process many fish have go through during puberty: sex change. Many fishes are born as one sex, but will turn into the opposite sex as they grow up. The best known example are clownfishes, which are all born as a male, but turn into females later in life. Including this process would have made “Finding Nemo” a much more interesting film in my humble opinion. Other species, such as parrotfishes and wrasses are born as females, but then turn into males as they grow up. While surprising to most people, the whole sex change thing is actually very common in the ocean.

Part of growing up in humans is learning to appreciate different kinds of food: whether it’s vegetables, olives or alcohol, children like different things than adults. The same goes for many fish species. Frogfishes for example start by mostly eating small shrimp, and then evolve a more delicate palate including fish like seahorses, lionfish, or pretty much any other fish that fits in their mouth. Interestingly, for frogfish growing up can mean that you start of as prey for a fish, but turn into a predator for that same fish once you’re big enough. Conclusion: growing up can be difficult for any animal, but some have it worse than others.