Coelacanth: Living Fossil

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

“Resolving the Phylogenetic Position of Coelacanth: The Closest Relative Is Not Always the Most Appropriate Outgroup”, by Naoko Takezaki and Hidenori Nishihara, Genome Bill Evil, 2016Apr; 8(4): 1208-1221, https://onlinelibrary.wiley.com/doi/10.1002/bies.201200145#sec1-3-title

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.

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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.

 

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.