“Microstructure of dental hard tissues and bone in the Tuatara denture, Sphenodon punctatus,” by J.A. Kierser, T. Tkatchenko, M. C. Dean, M. E. H. Jones, and N. J. Nelson. Front Oral Biol. 2009:13:80-85. https://pubme.ncbi.nlm.nih.gov/19828975
Music written and performed by Katherine Camp
Transcript
(Piano music plays)
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Kiersten - Welcome to Ten Things I Like About… This is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
We have made it to the seventh episode of Tuatara and the seventh thing I like about these super cool reptiles is their diet and dentition. We have hinted a bit about what they eat but today we’ll take a closer look at what that is specifically and how their teeth help.
Let’s start with food. Tuatara are carnivores. They eat mainly invertebrates like worms and arthropods such as beetles, millipedes, spiders, and weta. Weta are insects native to New Zealand that look similar to crickets but like crickets on steroids. Weta have big bodies, spiny legs, and tusks. They look kind of like a cricket and a warthog had a baby.
The majority of the tuatara diet is made up of invertebrates but they will also eat lizards, seabird eggs and chicks, and occasionally they venture in to cannibalism and will eat young tuatara. Because of this, juvenile tuatara are active during the day while adult tuatara are active at night. I mean, really, if your relatives might eat you at night, then who wouldn’t want to avoid them.
Humans that live on the islands where tuatara are found always know when they’ve been hunting because they will see headless birds. Definitely not something you want to come across on a relaxing walk in nature. Why is this the indicator of the tuatara?
The tooth pattern of the tuatara is unique. Just like almost everything else about them. They have two incisor like teeth in front of their top jaw. And they have three rows of teeth (I was not able to find an actual count but am guessing it’s around 85 teeth). One row of teeth lines the bottom jaw and two rows line the top jaw. The bottom row of teeth fit neatly into the two upper rows of teeth when the jaw is closed. Wait for it, we almost have our answer. The jaw motion of the tuatara is also unique. Instead of an up and down motion, like chewing, they have a forward and backward motion, like sawing.
And there it is! This is why the birds that tuatara hunt are missing heads. They saw them off with their unique teeth. Hah! Didn’t see that coming did you?
Besides the unique pattern of teeth, the structure of their teeth is also unique. They have acrodont teeth which means they are rootless and attached directly to the bone of the jaw. They kind of emerge from the actual bone. This is unlike any other reptile teeth alive today. The teeth are serrated which helps with the sawing motion. Tuatara cannot replace lost or cracked teeth. Once the tooth is gone, it is gone. As tuatara age their teeth wear down from use. They are eating crunchy invertebrates and bony vertebrates, so they do take a beating. Tuatara can live for up to 100 years, so the older tuatara have to switch their diet to softer prey as their teeth wear down.
Now for a long time, we thought they didn’t have real teeth. We thought they were just bony protrusions that stuck out of the jaw, but some researchers in 2009 looked more closely at the teeth. They looked at teeth from a juvenile as well as an adult and found layers of typical tooth material. This was a surprise.
Using Scanning Electron Microscopy, which is a sophisticated imaging technique that uses an electron beam to examine the surface of various materials, researchers found evidence of enamel containing dentine tubules, dentine, and cementum. All of these are found in other types of teeth. It’s not just serrated, bony material sticky up in their mouths. They have actually teeth. They are different then your average tooth, but they are teeth none-the-less.
These tuatara are just full of surprises!
I hope you enjoyed our dental adventure because my seventh favorite thing about the tuatara is what they eat and how they eat it!
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another exciting episode about the tuatara.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
Tuatara: Living Fossil
Episode 142
Thursday, January 29, 2026 • Duration 07:33
Summary: The term “living fossil” is a bit controversial but does it fit the tuatara? Join Kiersten to find out.
For my hearing impaired followers, a complete transcript of this podcast follows the show notes on Podbean
Show Notes:
“New study shows modern tuatara are little changed from 190 million year old ancestors.” Harvard University Department of Organismic and Evolutionary Biology, March 2022. https://www.oeb.harvard.edu/news
Music written and performed by Katherine Camp
Transcript
(Piano music plays)
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Kiersten - Welcome to Ten Things I Like About… This is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
The sixth thing I like about the tuatara is how long they have lived. Just like another animal we have talked about, the coelacanth, the tuatara appears in the fossil record from way back in time. The first time we see the tuatara in the fossil record is during the Jurassic period. Now, of course, a certain book and movie series has made this a very popular time in Earth’s history, so you may be familiar with this time period. It is famous for being the age of dinosaurs, at least some of the most popular and recognizable dinosaurs.
The term living fossil has been tossed around in reference to the tuatara, as well as the coelacanth, but this term is controversial. It is quite the romantic phrase actually. To think that an animal is so well adapted to the world it lives in that is hasn’t changed since the first time it appeared on this planet is a notion that a lot of us want to believe, but is it true? The first major problem with this concept, is that there is no real definition of what makes an animal or plant a living fossil.
Ants: Arboreal Ants
Episode 133
Wednesday, October 29, 2025 • Duration 09:57
Summary: How do colonies of ants live in trees? Find out in this episode about arboreal ants.
For my hearing impaired followers, a complete transcript of this podcast follows the show notes on Podbean
Show Notes:
“Adventures Among Ants” by Mark W. Moffett
Music written and performed by Katherine Camp
Transcript
(Piano music plays)
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Kiersten - Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
We are rounding the bend with the ants series and there is no better way to do that than to take to the sky. The title of this episode is Arboreal Ants. There are ants that live in trees and never touch terrestrial earth their entire lives. You thought the Leafcutter ants were amazing, well hold on to your hat because the seventh thing I like about ants is the colonies that live in the trees.
Arboreal ants, which are ants that live in trees, are found on many different continents and there is more than one species, but we are going to focus on one species in particular so we can really see their amazing qualities in detail. We’re spending some time with the Weaver ants of Africa, Oecophylla longinoda. Now living in a tree for an ant is no small feat, so how do they do it? Terrestrial ants dig into the dirt and create many chambered nests. It’s kind of difficult to dig into a tree, so where are arboreal ants living?
Coelacanth: Limbs vs Fins
Episode 42
Wednesday, August 2, 2023 • Duration 10:46
Summary: Are they limbs or are they fins? What are those things on the side of the coelacanth? Join Kiersten and a guest host to find out!
For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
This episode continues the coelacanth and their crazy interesting fins is the eighth thing I like about this deep sea fish.
Today I have a guest cohost joining me, my friend Casey. Thanks for joining me Casey.
Coelacanth: Reproduction
Episode 43
Wednesday, July 26, 2023 • Duration 10:19
Summary: Coelacanth reproduction is the most mind-blowing episode yet! Join Kiersten as she digs deep into the life cycle of this ancient animal.
For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean
“New Scale Analysis reveal centenarian African coelacanths,” Kelig Made, Bruno Ernande and Marc Herbin, Current Biology 31, 3621-3628, August 2021. https://doi.org/10.1016/j.cub.2021.05.054
“Latimeria, the Living Coelacanth, Is Ovoviviparous,” by c. Lavett Smith, Charles S. Rand, Bobb Schaeffer, and James W. Ate. Science, 12 Dec 1975, Vol 190, Issue 4219, pp1105-1106; https://doi.org/10.1126/science.190.4219.1105
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Coelacanth: Hunting and Diet
Episode 41
Wednesday, July 19, 2023 • Duration 11:26
Summary: How does this deep sea fish find food? Just like everything else with the coelacanth, it’s fascinating! Join Kiersten as she explains how the coelacanth hunts and what it likes to eat.
For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean
Show Notes:
“The coelacanth rostral organ is a unique low=resolution electro-detector that facilitates the feeding strike,” by Rachel M. Berquist, Vitaly L. Galinsky, Stephen M. Kajiura, and Lawrence R. Frank. Scientific Reports 5, #8962 (2015) https://doi.org/10.1038/srep08962
“The first direct evidence of a Late Devonian coelacanth fish feeding on conodont animals,” by Michel Zaton, Krzysztof Broda, Martin Qvarnstrom, Grzegorz Niedzweidzki and Per Erik Ahlberg. The Science of Nature 104, #26 (2017), https://doi.org/10.1007/s00114-017-1455-7
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
Coelacanth: Living Fossil
Episode 40
Wednesday, July 12, 2023 • Duration 09:32
Summary: Is the coelacanth a ‘living fossil’? Join Kiersten and a guest co-host as they discuss this controversial topic.
For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean
Show Notes:
‘Coelacanths as “almost living fossils”’ by Lionel Calvin and Guillaume Guinot, Front. Ecol. Evol., 13 August 2014, https://www.frontiersin.org
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
This episode continues the coelacanth and the controversy about whether they are a living fossil or not is the fifth thing I like about this ancient animal.
Today I have a guest cohost joining me, my friend Casey. Thanks for joining me Casey.
Coelacanth: Behavior
Episode 39
Wednesday, July 5, 2023 • Duration 09:21
Summary: What are those coelacanth doing in the deep water of the ocean? Join Kiersten as she discusses some of the coelacanth’s behavior.
For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean.
“New Insights About the Behavioral Ecology of the Coelacanth Latimeria chalumnae Video Recorded in the Absence of Humans Off South Africa” by Jiro Sakaue, Kazuhiko Maeda, Micheal J. Miller, Ryuichi Sakai, Koh-ichi Tahara, Hideki Abe, Kazuya Made, and Hitoshi Ida, Front. Mar. Sci., 10 November 2021, https://www.frontiersin.org
Music written and performed by Katherine Camp
Transcript
(Piano music plays)
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
This episode continues coelacanths and the fourth thing I like about this enormous fish is their behavior.
Once again, I’m going to state that we are still learning new things about the coelacanth everyday, so what I talk about in this episode is what we currently know, but the future may bring different information.
Coelacanth: Habitat
Episode 38
Wednesday, June 28, 2023 • Duration 09:23
Summary: Where do coelacanths live? Join Kiersten as she talks about the habitat of the coelacanth.
For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean.
Show Notes:
A Fish Caught in Time: The Search for the Coelacanth by Samantha Weinberg
“Madagascar may be a secret stronghold for ‘living fossil’ fish” by Stephanie Pappas, www.livescience.com
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
This episode continues the coelacanth and their habitat is the third thing I like about this amazing animal.
We are still learning more and more about the coelacanth everyday. And one of the things we’re still learning about is their habitat. Where exactly do these behemoths live? The information I’ll give you in this episode is what we know to date, but the future could show us something different.
Coelacanth: Anatomy
Episode 37
Wednesday, June 21, 2023 • Duration 12:27
Summary: Join Kiersten as she takes you on a surprising journey from the head of the coelacanth to the tail.
For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean.
Show Notes:
A Fish Caught in Time: The Search for the Coelacanth by Samantha Weinberg
Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
(Piano music stops)
Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
This episode continues the coelacanth and their anatomy is the second thing I like about this ancient animal.
In the first episode we established that the coelacanth is a fish, so the anatomy should be like fish anatomy, right? Maybe, but this fish has been around for 400 million years and from comparisons between living specimens and fossils, they don’t seem to have changed much at all. So the coelacanth has some anatomical surprises that other fish do not possess.
Let’s start at the head of the coelacanth and work our way back. In the center of the snout there is a large jelly-filled cavity. It’s called the rostral organ. Scientists initially thought this might be an electrosensory organ for detecting weak electrical impulses given off by prey. This hypothesis was supported by examining the organ’s intricacies including nerves and how it interacted with the brainstem. When submersible exploration became available to scientists, we were able to test this on a living coelacanth. Using electrical fields, researchers confirmed that coelacanths do indeed respond to electrical fields under water. There is no other vertebrate, that we know of, alive today that has a rostral organ. So we’re already off to an interesting start. Let’s see what else the coelacanth has that other animals may not!
Charles Darwin coined the term “living fossil” in 1859. According to Darwin’s definition a living fossil is a species or group of species that is so little changed that it provides an insight into earlier, now extinct, forms of life. A living fossil can also be described as an organism that has remained relatively unchanged over millions of years, or one that has no, or very few, close surviving relatives.
It certainly sounds like we have stumbled on another controversy here. In the last episode we answered the question of whether the tuatara is a lizard or not. Spoiler here, listeners, if you haven’t heard the previous episode and you don’t want a spoiler to this question, stop listening now and go back and listen to last week’s episode. With that warning, let’s move on. We have established that tuatara are not lizards, they are reptiles but not lizards for various reasons. Shall we jump into the next controversial question then?
Are tuatara living fossils? Let’s look at Darwin’s definition first. How much have tuatara changed since they first appeared in the fossil record? A 2022 study from Harvard University’s Department of Organismic and Evolutionary Biology may give us some insight. Tuatara are the last remnant of the Rhynchocephalians. These reptiles peaked in abundance in the Jurassic period. Then they disappeared from the fossil record.
Two researchers were looking through the archives in the Harvard Museum of Comparative Zoology and came across something that had been sitting in the drawers for decades, a tuatara fossil. This fossil was discovered in northern Arizona in the Kayenta Formation of the United States in 1982. Professor Stephanie Pierce and postdoctoral fellow Tiago Simoes jumped into examining this forgotten fossil. They used micro-CT scans to examine the fossil in three dimension. Then they digitally pieced the puzzle together revealing a full unflattened skull. It greatly resembled the modern day tuatara. It had rows of interlocking teeth that extended directly from the bone and it had two holes behind the eyes, just like the modern day tuatara.
Pierce and Simoes named the fossil Navajoshenodon sani which means “old age” in the indigenous language of the Navajo. This fossil provides the first nearly complete skull of any fossil sphenodontine in the world. It also places the tuatara in the Late Triassic. They may be older than we thought.
So how does this help us determine the answer to the living fossil question? It does give support for both descriptions. The modern day tuatara is similar enough to the fossil that it gives us insight into a long dead relative, and it seems to have changed very little from the long ago fossil of a creature that roamed the planet with dinosaurs.
Unlike the coelacanth, which is definitely not a living fossil, maybe the tuatara is a living fossil. It is food for thought and that is one of the reasons I started this podcast.
I hope you will continue to think about this small living fossil controversy because it is my sixth favorite thing about the tuatara.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another exciting episode about the tuatara.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
Weaver ant nests are most common in the outer, uppermost branches of trees where the sun light is bright. Here, the ants will bind adjacent healthy leaves together to create a treetop tent. The size of each nest will vary but is often between the size of baseball or a volleyball. They are as light as an inflated ballon and can withstand wind, rain, and enemy invasions. To begin building a nest, a worker ant will pull the edge of a leaf toward the edge of another leaf. If her bending is successful other workers will come to her aide.
Now weaver ants get their name from the next step. To keep the leaves together they employ their larvae. If you’re think, “What?” I hear ya! The larvae are picked up by workers and taken to the edge of the leaf connection. The workers tap the larvae on the leaf to encourage the larvae to release silk. Yes, the larvae of many species of ants create silk. The Weaver ants use this silk to secure the leaves together. The motion of shuttling the larvae back and forth to connect the leaves with the silk is where the weaving comes in. The nests may last for years because when one leaf dies the ants will just weave in another living one.
The nests are larger enough to house thousands of ants, but the weaver ants don’t have just one nest in the tree. They travel all over the tree that they call home, so they often build other trees op tents so they can maximize their resources. They don’t stick to one central nest, they have the ability to move around when they need to. One territory can have multiple nests. The queen is often in a nest that is the most centralized to the territory, but her eggs are distributed throughout all the nests.
With all of these spread out workers, Weaver ants have to have an excellent communication strategy. And boy, do they! Earlier we learned that pheromones are integral to ant communication. It’s the same with weaver ants, but they have a specialized gland that helps the pheromones that they use to create their paths last longer than terrestrial ants. They have an anal gland that helps them make their poop a bit more than just poop. To keep their pathways from wearing away too quickly, weaver ants use their feces to create longterm smell paths. The droplets of worker excrement hardens into a shellac like substance that can last for months.
This form of communication also allows these ants to do something most other ants do not, defend a specific territory. Weaver ants are known to defend their treetop territories from other ants they encounter. With the pheromone lines drawn already it gives them an advantage in skirmishes. Their scent is already laid down. If a weaver ant encounters an enemy worker, she will race back to more familiar territory to recruit help. She does this by mimicking fighting motions and other workers will follow her prepared for battle.
So what do weaver ants eat? This species of ant is omnivorous. They eat both meat and veggies. One of the coolest things they target is nectaries created by trees. These are spots on the leaves of trees that seep nectar. This isn’t like the sap that leaks from the tree’s bark, this is like the nectar that a flower produces. When they find a nectary, the weaver ants will built a tent around it to hide it from other animals that might be interested in this pot of gold as well.
Weaver ants do eat meat in the form of other insects, Mark Moffett retells an experience he had in Cambodia as he watched some local Oecophylla drag a 5 cm long scorpion up a tree to pull it apart, as well as other meat items such as birds, bats, and other ants. The protein is eaten mainly by the larvae while adults typically consume sap and nectar.
Does the tree benefit from the ants in residence or are they detrimental? This is a question that ecologists try to answer through cost/benefit analysis. Some benefits to the tree are weaver ants culling leaf eating insects before they can defoliate the tree. Foliage lasts longer in areas where the weaver ants live. The ants also provide a bit of fertilizer to the tree as well by pooping on the leaves. Trees can absorb some nutrients through their leaves. On the cost side, some of the leaves the weaver ants use to create their nests are permanently lost, but considering the small percentage of leave the ants use, I think the benefits outweigh the costs.
I hope this quick foray into the treetops with these arboreal ants was worth it, because treetop living ants is my seventh favorite thing about ants.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another exciting episode about ants.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, my very own piano playing hero.
Casey: You’re welcome. Thanks for having me.
Kiersten: Casey and I have known each other for a long time. We met as zookeepers 18 years ago and became friends very quickly. Today, Casey is a biology teacher and when she found out I was doing this podcast she was excited to help me.
Casey: Coelacanths are extremely interesting and their appendages, or limbs, are interesting in their history.
Kiersten: Great! Today we’re talking about limbs versus fins! I hope by now, listeners, you’ve all googled a picture of the coelacanth and have gotten a glimpse of their interesting fins. In episode two, anatomy, I talked about the coelacanths special fins called lobed fins. They have six lobed fins.
Casey: I love their little limbs!
Kiersten: Me too! But I thought they were fins?
Casey: They do look like limbs.
Kiersten: I think we need to dive into this topic and learn a bit more.
Casey: I agree!
Kiersten: Let’s start with some definitions. The Oxford Languages Dictionary says a limb is "a leg or arm of a person or a four-legged animal, or a bird’s wing”. That completely leaves out the coelacanth, for sure!
Casey: I agree! But the Merriam-Webster Dictionary definition is “one of the projecting paired appendages of an animal body used especially for movement and grasping but sometimes modified into sensory or sexual organs.” I think that puts the coelacanth back in the limb arena!
Kiersten: Maybe…Let’s hear Oxford Languages Dictionary’s definition of fin: “a flattened appendage on various parts of the body of many aquatic vertebrates and some invertebrates, including fish and cetaceans, used for propelling, steering, and balancing.” That definitely sounds like the coelacanth.
Casey: I can’t argue with that! But Merriam-Webster’s definition of fin is “an external membranous process of an aquatic animal used in propelling or guiding the body.” I’m on the fence with this one. I wouldn’t say that coelacanths have membranous fins.
Kiersten: Hmmmmm….I think what we need to do is look at what these fins can do.
Casey: You mean limbs.
Kiersten: Let’s call them appendages until we get his settled.
Casey: Deal!
Kiersten: The coelacanth has seven appendages overall. Four are paired, two behind the gills, the pectoral fins, one on each side; two mid body on the bottom of the fish the pelvic fins, one on each side. Then there is one anal fin just in front of the tail on the underside of the fish and then two dorsal fins. They have eight if you include the tail. I think it’s interesting in itself that they have eight appendages, that’s quite a lot for a fish.
Casey: Yeah, what are they using all those appendages for?
Kiersten: Well the four paired fins on each side of the body move like paddles propelling them forward through the water. These appendages are able to rotate 180 degrees so they can probably use them to back up as well as more forward. The really cool thing about these four extremities is that they work in conjunction with each other. The right pectoral fin moves together with the left pelvic fin.
Casey: You mean like the way a horse walks?
Kiersten: Yes! It’s a lot like how a many land mammals move their ….. oh, I see where you going with this. You just want me to say they're limbs!
Casey: Yes! Yes, I do!
Kiersten: Well, I think we might both get what we want from the next definition. Coelacanths are classified as a lobe-finned fish. This means that the flouncy part of the fins are attached to a stalk that projects out from their body. It actually looks like a paddle with a fin attached to the end.
Casey: That sounds like a limb…..and a fin.
Kiersten: Yes, I agree. Maybe we can agree that we’re both right?
Casey: I can do that. Did you know that some lungfish, who are also a lobe-finned fish, actually use their fins to walk on land when they need too? If the vernal pond they are living in becomes too shallow, they can use their limbs to drag themselves across the land to another water source. Essentially they use their limbs to walk to another pond.
Kiersten: I guess it really is both a limb and a fin. Speaking of limbs, I just read a research paper, from way back in the early 2000’s, that stated a coelacanth fossil actually helped scientists understand the evolution from fins to limbs in tetrapods. Tell us little about that.
Casey: I can! What you’re talking about is called evolutionary classification which is a strategy that we tend to use now instead of taxonomy which only looks at physical attributes. Evolutionary classification is grouping organisms together based on their evolutionary history. So, we’re looking at lines of evolutionary descent not just physical characteristics. These lines are called cladograms and they look like trees. They branch off at each different change. So, the cladogram where it’s branching off to tetrapods, which is a four limbed vertebrate, is where their is a bit of a controversy involving the coelacanth.
We are tetrapods. We may walk on two legs but we have four limbs. The big debate is whether the kingfish or the coelacanth is the direct ancestor of tetrapods. Now remember we said lungfish walk on their limbs to get to the next vernal pond. That is where the debate is coming from. I’d like to say there is an answer to this debate but there are three different cladograms and only one of them has the coelacanth as the direct ancestor to the tetrapod.
Kiersten: Is it descendent or ancestor?
Casey: It’s ancestor.
Kiersten: Okay. Because we’re all tetrapods, right?
Casey: Right, but we would be a descendant of a coelacanth. Now I’m not talking like you grandmother or anything.
Kiersten: (laughs)
Casey: I’m talking millions of years ago. So coelacanths or lungfish would be the ancestors of tetrapods. One version has the coelacanth as the direct ancestor, while another version has the lungfish as the direct ancestor, and the last version has both of them at the same branching. So, no solution to this debate as of yet. They’ve narrowed it down to these three options. No mater how you look at it though the coelacanth is Number 1 or Number 2.
Kiersten: So, he’s still winning. (Laughs)
Casey: (laughs) Yes! He’s still winning. He still in the trifecta. Either way it’s still in the positive.
Kiersten: That is interesting! That’s why I picked you for this podcast! I knew you’d understand that and be able to explain it better than me! Thanks for helping me talk about the coelacanth appendages today Casey.
Casey: You’re welcome. I had a lot of fun!
Kiersten: Me too! And I think we both agree that coelacanth appendages are both limbs and fins.
Casey: I agree!
Kiersten: Well that is it for this episode, listeners. I hope you enjoyed a little debate about coelacanth appendages because it’s my eighth favorite thing about them.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another episode about the coelacanth.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
This episode continues the coelacanth series and the seventh thing I like about them is how they reproduce.
Strap in for this one listeners because this is the most mind-blowing episode of the coelacanth so far!
There are so many unbelievable facts about coelacanth reproduction I almost don’t know where to start, but I have to start somewhere, so let’s start with their maturation age.
Coelacanths are large fish averaging about five feet long with some individuals reaching six feet. With most large animals it takes some time to become mature enough to reproduce. For example, it takes elephants approximately ten years before they are ready to reproduce, blue whales, the largest animal alive today, mature around 15 years old, and Goliath groupers, a fish that can reach almost 8 feet in length, mature at about 20 years old. The coelacanth is no exception to this trend but they push it even farther than these three examples. A coelacanth becomes sexually mature at 55 years of age. That is an awful long time to survive before you can make more coelacanth.
When coelacanths are ready to reproduce, a mate must be chosen. We don’t know what goes into this decision because we have not seen coelacanths copulating, yet. We don’t know what females look for in a mate, we don’t know if there is a mating ritual that males perform to attract females. We do know that most likely females choose the male and allow him to mate with her because fertilization is internal in coelacanths. I say this because other males of species that have internal reproduction or internal fertilization have various behaviors to attract females to them. The females pick the males that impress them most based on established criteria such as feather color, winning a fight with another suitor, or singing the best song.
We’re already off to an unusual start because most scaled fish reproduce externally by laying eggs with males fertilizing the eggs after they are laid. Internal fertilization in fish such as sharks and rays is common but not so much in scaled fish.
We do know with some certainty that coelacanths are probably monogamous. In a scientific paper published in 2013, researchers genetically studied two clutches of coelacanth eggs and their mothers. Both coelacanth females were Latimeria chalumnae, the African Coelacanth. One female had 26 embryos and the other had 22 embryos. Both clutches appeared to be close to birth when the females were caught and perished. Let’s call the females with 26 embryos Clutch 1 and the female with 22 embryos Clutch 2. Results revealed that all the young of clutch 1 had four genotypes present. These were contributed by two individuals. The same results were reported for clutch 2. What exactly does this mean? It means only one male contributed his genetic material to the embryos. It was a different male for each female, but only one male contributed to the embryos. It’s an extremely small sample size, but this leads us to believe that coelacanths are monogamous. The females, at least, may only mate with one male at a time.
Coelacanths are classified as ovoviviparous. For those of you who have listened to my caecilian series and remember the reproduction episode, you already know that ovoviviparous animals give live birth to animals that they incubate inside an egg that remains inside the female during development. This is what the coelacanth does. Now, you might be wondering how we know this since so much about their reproduction is still unknown. And that’s a great question, how do we know?
In 1975, a gravid female was caught and upon dissection at the American Museum of Natural History, researchers found five young developing inside the oviduct of the coelacanth. These five young were attached to large yolk sacs. Since then other gravid females have been caught, as well, and dissection of these specimens has supported the findings of 1975. The female with 26 young in her oviduct appears to be the largest clutch discovered so far.
Coelacanth eggs are pretty big. They are approximately 3 1/2 inches in diameter. Compare that to the average chicken egg at a diameter of 1 1/2 inches and you get a feel for how big their eggs get. When the young are born they are around 12 inches in length and they look like tiny versions of their parents. How long does it take a 3 1/2 inch egg to become a 12 inch fish? Probably longer than you think.
Coelacanth females carry the young for up to five years. This is the longest gestation period of any animal that we are aware of at the recording of this podcast. Some species of sharks carry the young for three years. The coelacanth has them beat and it also explains why their eggs are so large. They need a good, long-lasting source of nutrition to develop properly.
Once the young are born, we lose track of them. With the research we’ve been able to do with live coelacanths, we haven’t seen any young hanging around with adults so we assume that they must retreat to another habitat. There could be many reasons for this. They are much smaller than a full grown adult so they presumably eat different prey which means they could need a different environment in which to hunt. They might be escaping from their own parents territory because mom and dad might eat them. They may even move to higher depths or lower depths until they are much larger in size. Whatever the reason we have not seen any juvenile coelacanths, so for now their whereabouts remain a mystery.
The last thing we know about coelacanth reproduction is how long they live. For many years we thought they lived about 20 years and that they were extremely fast growing, but a study released in 2021 changed that.
One way to determine a fish's age is to count the rings on their scales. Initial studies of coelacanth scales suggested a 20 year life span, but using a new technique involving polarized light researchers were able to see all the rings on the scales. The new data revealed that coelacanths can live up to 100 years. 100 years! This is also the study that determined they become sexually mature at 55 and they have a gestation period of five years. Who knew the rings on a fish’s scales could tell us so much?
That’s all for coelacanth reproduction. I still can’t get over all the amazing things I learned researching this episode and I know you are just as intrigued because it’s my seventh favorite thing about coelacanths.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another episode about the coelacanth.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
This episode continues the coelacanth and their diet and how they hunt is the sixth thing I like about them.
If you remember from episode two, Anatomy, coelacanths have what is called a rostral organ. This organ is believed to help them detect electric fields in their environment. Why do they need to detect electric fields? I love this question, listeners, and I’m proud of you for asking it! Some fish have the ability to detect weak, low frequency electric fields produced by living tissue that is in contact with water. These fish typically have some kind of electrosensitive organ that detects the electric fields and these fish tend to be meat eaters. See where I’m going with this?
The electric fields that living creatures give off is how the coelacanth finds its food. Let’s delve into the details of their rostral organ and see how this thing works.
Most fish with an electrosensitive organ that have been studied have complex labyrinths of hundreds to thousands of sensory canals. These canals are distributed throughout both the top and bottom of the head and are also often found around the mouth. These canals are typically arranged in clusters that are reminiscent of a directional antenna. All of the canals connect to an electrosensitive organ. The layout of the canals allows the fish to sense other animals near it from several different directions. This can help them find food, recognize conspecifics, or detect predators when they are at close range. Every animal’s electric field will be different and our fish can use those differences to discriminate between the animals near them.
The coelacanth’s rostral organ is an electrosensitive organ but, just like everything else we’ve learned about so far, it’s not quite like other fish’s. To discover more about this organ, a team of scientists used an MRI machine on a preserved specimen of Latimeria chulumnae to get a good look at it. What they found was slightly unexpected but explained a few things that we’ll talk about in just a moment.
The rostral organ of the coelacanth has only three sensory canals, as opposed to hundreds or thousands seen in other extant species of fish. These canals are called tubules and they are all restricted to a small area of the upper snout. They also have no electroreceptors connected to the lower surface of the snout or lower jaw. Seeing the smaller scope and size of the rostral organ, the researchers asked what good is it really doing the coelacanth.
Using the 3D images they got with the MRI, they approximated the sensitivity of each tubule which allowed them to estimate the range of the rostral organ. What they found was that the coelacanth can only detect animals directly in front of their snout. Their rostral organ is only a low-resolution electro-detector so they do not get any complex information from the electric fields they detect and the field must be very close to them.
This makes them unique in living fishes that use electrosensory organs to detect prey because they cannot track the prey items movements. They have to wait until the prey is practically in their mouths before they sense them. Remember I said this studies’ findings explained something about the coelacanth, well the is it. It explains why they hunt the way they hunt.
When we first developed technology that allowed us to study live coelacanths in situ, we noticed a strange behavior. Sometimes coelacanths would drift along in a current with their heads down and their tails up, essentially in a headstand posture. We had no idea what was going on, until someone saw them snatch a fish. This is the way coelacanths hunt.
It’s called drift hunting and it’s a passive way of hunting. The fish just floats along with the current of the water and waits for the right prey to come along. Then BAM!, dinner is served. This explains why their rostral organ is so focused on the snout region of their body.
Once the coelacanth’s rostral organ indicates that an appropriate prey item has approached within 10 to 20 centimeters in front of its mouth, it snatches it out of the water. The specific feeding mechanism of the coelacanth is called suction-inhalation. I don’t think that really needs too much explanation. They suck their food into their mouth along with large amounts of water. This does explain why the coelacanth has such a large mouth. If you’re sucking your prey in whole, you want to have a big mouth.
Coelacanths have well-developed protrusible jaws that are capable of great forward motion. Their extremely muscular lower jaw also contributes to their powerful suction-inhalation. They also have an expandable gular structure, under the chin, that helps increase the power and gape of the mouth. The intracranial joint that coelacanths have retained, while other species of fish have lost it through millennia of evolution, may also help with the flexibility of the head which in turn helps with mobility of the jaws.
This suction-inhalation does allow them to hunt animals that other fish of their size cannot reach. Researchers have seen coelacanth suck animals out of hidey holes in craggy canyon walls. And this method of cap ture is fast! It takes only a second for the coelacanth to inhale a prey item.
Inside the mouth, coelacanths do have three types of teeth. It does not appear that they use the teeth for grinding or shredding their food. It is more likely the teeth are there to prevent prey from escaping their giant maw.
Now that we know how coelacanth find their prey, what kind of prey are they looking for? This is a good episode for great questions, listeners. Y’all are on a roll today!
Coelacanths are classified as piscivores. Pisces is the Latin word for fish, but those of you born between February 19th and March 20th already knew that! So a piscivore is an animal that eats fish. Coelacanth are not terribly picky about what they eat and their diet can include cuttlefish, squid, octopus, snipe eels, small sharks, and other benthic fishes. So, essentially whatever fits in their mouth.
It appears they’ve been eating like this since the beginning of their time on earth. In a research paper published in 2017, the first direct evidence of a coelacanth eating eel like animals was discovered in the digestive tract of a fossilized specimen found in Poland. The coelacanth came from the Late Devonian period and a remnant of the eel was found preserved in the digestive tract. They also found coprolite, fossil poop, possibly from the coelacanth with the same remnants inside. We can’t know how these coelacanths hunted their food but we can now say that they’ve been eating the same kind of food for quite some time.
In 2000, researchers looked at where coelacanths hunted, how abundant prey items were where they hunted, and how much food they might be eating.
They found that coelacanths hunted between 650 feet and 1300 feet below the surface of the water. They also measured prey density in relation to depth which increased as you descended deeper. I was a bit surprised by that actually. I thought there would be less prey as you moved further down. Maybe I need to do another series on some deep-sea wildlife.
They also estimated how much food the coelacanths were eating during each hunting session. Assuming the individuals studied were 100% successful on each hunt, medium-sized individuals were consuming about 122 grams of food and large females were consuming 299 grams of prey. Doesn’t seem like a lot considering an average sized Gala apple weighs between 150 to 250 grams. Although, an apple a day…right?
That’s all for this episode on the coelacanth. I hope you found their hunting behavior and their diet as fascinating as I did because it is my sixth favorite thing about them.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another episode about the coelacanth.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
Casey: You’re welcome. Thanks for having me.
Kiersten: Casey and I have known each other for a long time. We met as zookeepers 18 years ago and became friends very quickly. Today Casey is a biology teacher and when she found out I was doing this podcast she was excited to help me.
Casey: I excited to talk about the coelacanth.
Kiersten: When the coelacanth was first rediscovered in 1938 by the Marjorie Courtaney-Latimer in East London, South Africa people immediately began calling it a “living fossil” with quotations because this fish had not been seen by modern humans expect in fossils. Today there is a big controversy over whether the living coelacanths actually qualify as a “living fossil.” Guess we should start off with a definition of “living fossil.”
Casey: Yes. One of the controversies is that there isn’t a real definition of living fossil.
Kiersten: Ah! I could see how that could be a problem, but I thought Darwin had defined living fossil back in 1859.
Casey: He coined the term but it’s not really a scientifically accepted word. It’s just not measurable in scientific terms.
Kiersten: Okay, but I think we should let my listeners know what it is and so they can follow along. According to Darwin’s definition a living fossil is a species or group of species that is so little changed that it provides an insight into earlier, now extinct, forms of life.
Casey: It can also be described as an organism that has remained relatively unchanged over millions of years, or one that has no, or very few, close surviving relatives.
Kiersten: Well that certainly sounds like the coelacanth to me!
Casey: Me too! But not all scientists agree.
Kiersten: I’ve heard of some researchers using RNA sequencing to determine whether they are living fossils. Can you explain this?
Casey: Certainly….You have to think about when the coelacanth was first discovered. In 1938 we didn’t have a way to sequence genetics. Even in the 1990’s when the second specimen was found we still didn't have the technology that we do now. We know now that the coelacanth have been changing internally all this time even if they still look very similar on the outside to fossil coelcanths.
Kiersten: Okay, so comparing this to Darwin’s definition, they may look the same on the outside but on the inside they are different. Genetically speaking.
Casey: Yes. And looking at the second definition that I gave, once the second species was found in 1998 it voids that definition. There are now two related species or close surviving relatives.
Kiersten: So we can’t call the coelacanth a living fossil any more. That’s kind of sad.
Casey: I think so too! It’s a neat phrase to use but not necessarily the best.
Kiersten: Let’s recap. The coelacanth looks physically the same because maybe the habitat is the same as years ago, and they do not need to change physically because their habitat is basically the same.
Casey: Correct, that could be one of the reasons. What they have seen geographically they haven’t seen much change on their habitat. Now. I’m not saying that their hasn’t been pollution or other similar changes but there have been no changes that cause them to change physically. Molecule or genetic changes are a different story. What scientists are looking at are RNA changes.
Kiersten: Okay. We hear a lot about DNA, not so much about RNA. What’s the difference?
Casey: DNA is deoxyribonucleic acid while RNA is ribonucleic acid. They are looking at RNA to determine where coelacanth fall on the phylogenetic trees. Who are they more closely related to and such. The RNA changes are helping them determine that.
Kiersten: So, internally we have some changes but externally not so much.
Casey: Yes.
Kiersten: Thanks, Casey for this interesting debate and explaining RNA and living fossil research on the coelacanth!
Casey: Thank you for having me. I think coelacanths and their history are extremely interesting.
I hope you all enjoyed this look into the living fossil debate because it’s my fifth favorite thing about the coelacanth.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another episode about the coelacanth.
If you’ve heard any strange noises on today’s episode, that’s Edison, Casey’s dog who joined us today, as well.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
As I mentioned in the last episode, coelacanths are a deep water fish. They are typically found between 250 feet to1300 feet below the surface. We can see them using specialized scuba diving equipment called ‘rebreathers’ and by using submersibles. This technology has allowed us to study live individuals instead of the dead specimens that wash ashore or are, most often, caught as by-catch by fishermen. Because of this we know a lot about their anatomy, since many of the dead specimens have been dissected, but we don’t know as much about their behavior.
In the 1980’s studying coelacanths with deep sea vehicles became the common practice in the Comoros Island area. Between 1986 and 2009 we studied this population with submersibles and remote operated vehicles, or ROVs. Using their spot patterns we determined that this population contained approximately 300 to 400 individuals. We also observed their basic day to day pattern.
A day in the life of a coelacanth consists of resting in caves at a depth of 500 feet to 800 feet during daylight hours. They will share caves with other coelacanths and smaller species of underwater life. The caves are carbonate caves formed during underwater volcanic eruptions. During the night, coelacanths leave the caves to hunt in even deeper waters. At least one individual was seen hunting in waters approximately 2000 feet deep. That’s a third of a mile under the surface of the water! I can’t even imagine the pressure these fish endure.
In the Fall of 2000, a few individuals were encountered by divers in another area near South Africa called Jesser Canyon. This encounter actually was the first direct contact between humans and a live coelacanth. We then began focusing on this area, as well, to study the coelacanth. Between 2002 and 2004 submersibles were used to watch this area. Here they observed 21 individuals in 16 different locations in canyons off the coast of Sodwana Bay, South Africa. These individuals were seen at depths of 300 feet to 450 feet. These studies revealed that the coelacanths in this area were traveling between two canyons, Jesser Canyon and Wright Canyon.
Research begun in 2018 wanted do something that had never been done before, study coelacanths without the influence or interference of humans. If you noticed in all the research I’ve detailed so far, the common thread was the presence of a submersible, human diver, or mobile ROV. We have no idea how these things might change the behavior of the coelacanths observed. We do know that the presence of unknown stimuli, meaning divers or ROVs, can alter the natural behavior of wild animals.
These researchers used fixed cameras set up in a known coelacanth resting places to record the fish’s behavior without the presence of humans. They also wanted to record the ocean conditions such as temperature and current direction and velocity. To do this they placed two oceanographic recording devices near the study site. The main focus of this study was on the folding or unfolding of the first dorsal fin.
Now you might think, wow that’s a lot of work to look at one trivial little fin, but we’ve learned some of the most ground breaking things about animals by looking at one tiny little behavior, such as the eye movement of gorillas and the tongue flicking of snakes. This research actually shone a light on coelacanth behavior that we didn’t even know we should be looking for!
Okay, let’s take a moment to look at the iconic coelacanth image. If you haven’t yet googled the coelacanth, do so now and look at a few different photos of live coelacanths. Go ahead now, I’ll wait. Unless you’re listening to this podcast in your car. Do Not try to look up an image of the coelacanth if you are driving. Eyes on the road!
For those of you able to safely pull up images, look at that first dorsal fin. What do you notice about it in 98% of the pictures? It’s unfolded and standing up right, correct? I’m actually looking at the cover of the book A Fish Caught in Time by Samantha Weinberg right now and the first dorsal fin is erect in the illustration of the coelacanth on the cover.
Up until the 2018 research project, we thought this was just how the coelacanth naturally carried this fin. Now we did know they were capable of folding it up and down and we assumed this fin was used for stabilization during swimming. We might have been wrong about that. According to the data collected in the absence of human interaction, the dorsal fin raises when the coelacanth encounters a stressor.
In this research it was a sand tiger shark. They got great video of a coelacanth and a sand tiger shark in the same cave during the day. The shark showed no antagonistic behavior toward the coelacanth but while the shark was in the cave with the coelacanth, that first dorsal fin was raised. When the shark left the cave, the fin relaxed. They were other species of fish in the cave with the coelacanth as well and the fin was lowered while they were present.
This sand tiger shark was larger than the coelacanth and might have posed a threat to the coelacanth. There isn’t any evidence that sand tiger sharks eat coelacanths but when you’re a potential prey item you’re not going to ask the shark if they going to eat you, you’re going to take action. Raising the dorsal fin may be a way for the coelacanth to look bigger and ward off predators. This type of behavior has been well documented in other species of fish.
This observation floored me. It means that the presence of humans and ROVs is considered stressful to the coelacanth and our presence was probably changing the behaviors we observed. If we want to know more about them, we’re going to have to come up with some unobtrusive methods of observation.
This research also studied temperature and currents near where the coelacanth were seen. Does this impact their behavior? It was observed that the coelacanth were present in the caves when the temperature of the water was between 59 degrees Fahrenheit and 71 degrees Fahrenheit. This has been seen in past research, as well. The researchers postulated that this is the optimal range for oxygen uptake in the coelacanth. The current direction was frequently southward and low in velocity when the coelacanths were seen at the study site, but more research will need to be done to determine if this is of any significance.
Wow! I don’t know about you but the coelacanth continues to amaze me. I’m glad you spent some time with me to learn about coelacanth behavior because it’s my fourth favorite thing about this ancient fish.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another episode about the coelacanth.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
When the coelacanth was discovered off the coast of South Africa eighty-five years ago we had no idea where it came from, but we did know where it was caught. The fisherman caught it off the coast of South Africa in the Indian Ocean at a depth of forty fathoms, or 240 feet. We didn’t see another one until 1952. This one was caught near the Comoros Islands which is off the southeastern coast of Africa in the Indian Ocean. Now we had an idea of where we might find more.
It wasn’t until later that researchers went to the islands and talked to the native islanders asking about this giant fish. (Quick note here, we should do more of this. Native inhabitants of areas that others explore know a lot about local wildlife. Why reinvent the wheel when you have so much information right in front of you, if you are just willing to listen?) Now, back to the coelacanth. Locals of the Comoros Islands were familiar with the coelacanth and had even eaten them in the past. Focusing on this area, several more coelacanth were found.
In 1998, more coelacanth were discovered in Indonesia, half a world away. The question was how did they get there? Did they migrate? Do they do that seasonally? Did a few get lost? Did they get washed away in a storm? Or have they been there this whole time? Turns out, they’d been there the whole time.
When the Indonesian coelacanth was discovered, scientists performed DNA tests to see if they were related to the African coelacanth or possibly a new species. Once again these ancient fish surprised us, the two populations were indeed two separate species. According to research available at the recording of this episode it looks like these two species may have evolved separately.
The African coelacanth’s scientific name is Latimeria chalumnae and the Indonesian coelacanth’s scientific name is Latimeria menadoensis. I mention this because they were named after Marjorie Courtenay-Latimer the discoverer of the first specimen in 1938 and I think it’s wonderful that this woman of science gets props for her discovery.
Before we get into where exactly these fish are found around the global let’s talk about at what depths they are found. This first specimen found in 1938 was caught by fisherman at a depth of 40 fathoms or 240 feet. For quite some time we thought this deepwater depth is where they lived. But we now know that they actually inhabit, mesopelagic waters, also known as the “twilight zone”, that reach depths of 650 feet to 1,300 feet. That’s a lot deeper that we thought or ever expected. We’re not sure why the original specimens were caught in the shallower depths, but they could have been hunting or they could have been ill and unable to control their swim bladders properly and floated up into shallower depths. More recent sitings of both species have been between 300-500 feet deep, so obviously these fish are doing something important at these depths. Now that we know at what depths the coelacanth can be found let’s look at where in the world we can find them.
Let’s investigate the habitat of the African coelacanth, Latimeria chalumnae, first. These coelacanth are found in the Indian Ocean near the coasts of southeastern Africa, Madagascar, and the Comoros. The first one found in 1938 was caught off the coast of South Africa but after that no more were seen in the area. More specimens were found near the Comoros islands, that are situated between Madagascar and the east coast of Africa, in the 1950s so it was thought that the first one found in 1938 was a stray individual from the Comoros area. But when diving technology advanced, divers using “rebreathers” which allow to you dive deeper underwater than typical scuba gear, and later on researchers using submersibles, saw resident individuals in South African waters. Specimens have been caught off the coast of Madagascar and off the coast of Mozambique and Kenya.
Latimeria menadoensis, also known as the Sulawesi coelacanth is from Indonesia. Two specimens were caught off the island of Manado Tua at the northeastern tip of Sulawesi. Later two more were sighted 225 miles southwest of this island.
In both regions, coelacanth inhabit temperate waters near steep rocky slopes of volcanic islands. In the daytime, the Comoran coelacanths can be found clustered together in caves in submarine lava deposits. In the evenings they venture out to hunt. The two individuals observed from a submersible in Indonesia were seen in a deep carbonate cave at a depth of 500 feet. Both species seem to depend on caves, canyons, and cliff ledges for almost all aspects of their life. Sleeping during the day and hunting at night seem to be done in and around these structures.
in 2021 researchers found evidence that Madagascar might be an unknown haven for coelacanths. In a new review of Madagascar fishery bycatch, 34 specimens were confirmed to be coelacanths. These catches have never been reported to scientists or conservationists before now. This indicates that coelacanth may be living off the coast of Madagascar.
When we look at the history of this large island off the coast of Africa, it could be completely possible. Coelacanth are actually older than the island of Madagascar by about 330 million years, but Madagascar has had a coast line for around 88 million years; whereas, the Comoros Islands is only 15 million years old. Based on this history and recent bycatch reports, researchers think that Madagascar might be their ancestral home. More research will need to be done to find out if this is true, but it just one more thing that adds to the mystery of the coelacanth.
I am so glad you went deep sea diving with me today to learn about the habitat and species of the coelacanth because it’s my third favorite things about them.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another episode about the coelacanth.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
Moving to the mouth we find teeth. That’s not entirely unique in fish that eat other fish and the coelacanth is a carnivore. They have three different shapes of teeth, one is a high, sharp cone-shaped tooth that could be called a fang, the second is a midsized, sharp cone-shaped tooth, and the last is a small rounded tooth. What is unique to the coelacanth is that the small rounded teeth are embedded in a bony dental plate that lies beneath their chin. We’re not entirely sure what the advantage of having a dental plate gives the coelacanth. In general, the teeth seem more like a way to keep fish in the mouth once they are sucked in versus tearing or chomping on their prey.
The eyes are just above the mouth and they are attached to thick optic nerves. The eyes are large. I’d say they are in proportion to their body and they are a five foot long fish, so…large eyes. Each eye does have a few cones, which allows for color vision, but they many rods, which help detect light. This is perfect for the coelacanth because they live deep under water where there is very little light available. The rods help them see in almost near darkness.
They also have something else that helps them see in the dark and this is a layer behind the retina of the eye called the tapetum lucidum. If you’ve ever seen light flash in your cat’s eyes at night, you’re seeing the tapetum lucidum. This layer acts like a mirror reflecting the light that comes into the eyes back out of the eye to increase the amount of light that passes over the retina. This enhances the coelacanth’s ability to see in low light.
Just behind the eye toward the top of the head is the intracranial joint. Until we rediscovered the coelacanth this joint had only been seen in fossils of primitive fish. This joint allows the coelacanth to open its mouth exceptionally wide to swallow fish and other prey. Two powerful muscles cross the intracranial joint providing strength to the coelacanth’s jaws. The coelacanth is the only fish alive that still has an intracranial joint.
Just under this joint and near the eye is the brain. The brain is small. It takes up only 1.5% of the brain case in mature adults. In a 90 lbs coelacanth the brain weighs less than a tenth of an ounce. That’s a pretty tiny brain. There is no extant vertebrate with this much of a difference between the size of the brain and the size of the body. Although, they have been alive for 400 million years so it must be working.
Coelacanths do have gills like other species of living fish and they are located behind the eye in the usual place that you find fish gills. They are relatively small in comparison to the overall body size, but they are similar to other fish species found at the same depth as the coelacanth. The relatively small surface area of the lungs is indicative of a slow-moving fish as opposed to an active fish. All the evidence we have to date does show that the coelacanth is a relatively slow-moving fish. When you’re a five foot long fish, you take your time getting places.
This large fish is covered in scales and those scales are woven tightly together like armor. I think that seems appropriate for such an ancient animal. The scales are hard and rough to the touch. Each scale has tiny, tooth-like spikes called denticles all over the surface which creates the roughness. The hard scales and denticles provide protection against predators and rocks. The scales are a beautiful steely-blue color with random white spots throughout. The pattern of the spots is unique to each individual and scientists have used that to their advantage. Researchers use the spots like name tags to identify individual coelacanth.
The fins of this fish are quite spectacular. They have six fins that are lobed and this puts them into a group of fish known as the lobed-finned fish. Lungfish and coelacanth are both included in this group. What’s the difference between a lobed fin and a normal fin? Great question! Lobed fins are fins that are attached to stalks that project out from the body rather than fins that are attached directly to the body. They look kind of like paddles sticking out from the side on the animal. The coelacanth has six lobed fins, one on each side just behind the gills called pectoral fins (2), one on each side of the pelvis called pelvic fins (4), one small secondary dorsal fin on the top of the body (5), and one anal fin on the underside of the body before the tail (6).
Overall the coelacanth has seven fins, not including the tail. The first dorsal fin is the only non-lobed fin. It’s larger than the other fins and attaches directly to the body. It can be raised and lowered to change its surface area.
We call the coelacanth a vertebrate because it has an internal skeleton which usually implies that it has vertebrae or bones of the spine. Once again the coelacanth surprises us. They have a notochord in place of a bony spine. A notochord is a thick-walled, fibrous, and elastic tube that is filled with oil. This is what the coelacanth has in place of a bony spine. Most creatures with a backbone replace the notochord with vertebrae in the embryonic stage. But adult coelacanth use the notochord for their longitudinal support.
Like almost all other fish species, the coelacanth has a swim bladder. Fish use the swim bladder to maintain buoyancy in the water. Most fish use air to inflate the swim bladder and they are able to modify the amount of air depending on the depth in which they wish to swim. I bet you didn’t see this coming but…, the coelacanth’s swim bladder is not filled with air! Okay, maybe you did see that coming. The coelacanth’ s swim bladder is filled with oil and fat, but it works the same as the air filled bladder, helping maintain buoyancy.
That brings us to the end of the fish, also known as, the tail. Hopefully, you’ve listened to the first episode of this series where I talk about the rediscovery of the coelacanth, if not definitely check it out. When Marjorie Courtenay-Latimer rediscovered the coelacanth in 1938, she described the tail as looking like a “puppy dog tail.” The tail is actually divided into three sections with a small tail fin in the middle. The tail is flat and powerful giving the coelacanth the ability to dart forward forcefully when catching prey or escaping predators. The tail can rotate and flex from side to side and is thought to help the fish with trim and balance.
That is all I have for coelacanth anatomy. Thanks for joining me on this head to tail adventure because it’s my second favorite thing about the coelacanth.
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Join me next week for another episode about the coelacanth.
(Piano Music plays)
This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
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