Podcast Summary: Stuff You Should Know – "Selects: How Coelacanths Work"

Episode Details

• Title: Selects: How Coelacanths Work
• Hosts: Josh Clark and Charles "Chuck" Bryant
• Release Date: July 5, 2025
• Description: Dive deep into the mysterious world of coelacanths, ancient fish once thought extinct, and explore their unique biology, discovery, and significance in evolutionary history.

1. Introduction to Coelacanths

Josh Clark [01:01]:
"We're gonna jump back in time to June 6, 2017 to talk about coelacanths. How coelacanths work. What in the world is a coelacanth? I think I kinda remember. Check it out right now."

Josh and Chuck introduce the topic of coelacanths, setting the stage for an exploration of these enigmatic creatures.

2. The Discovery of Coelacanths

Chuck Bryant [05:05]:
"It was quite a big surprise in the 1930s when a trawler... came in and... the world was saved." [05:05]

The hosts recount the astonishing discovery of coelacanths in 1938 by Marjorie Courtney Latimer off the coast of South Africa. Initially believed extinct for over 80 million years, the capture of a live coelacanth reignited scientific interest and provided invaluable insights into ancient marine life.

Josh Clark [07:06]:
"She picked away the layers of slime to reveal the most beautiful fish I had ever seen." [06:42]
Despite their unusual appearance, Latimer recognized the unique beauty and significance of the coelacanth, leading to its classification as a new species, Latimeria chalumnae.

3. Biology and Physical Characteristics

Josh Clark [06:56]:
"It was five feet long, a pale mauvey blue with faint flecks of whitish spots... covered in hard scales and it had four limb-like fins and a strange little puppy dog tail." [06:56]

Coelacanths are described as large, aesthetically striking fish with distinctive features:

• Four Limb-like Fins: Resembling legs, these fins are crucial for understanding their evolutionary significance.
• Rostral Organ: Located in the nasal region, filled with a jelly-like substance believed to detect electrical signals from prey.
• Hinge in the Cranium: Allows the head to retract, enabling the mouth to open exceptionally wide, facilitating the consumption of large prey.

Chuck Bryant [22:34]:
"They have a rostral organ... they think it detects low-level electrical signals and frequencies from prey." [21:41]

4. Evolutionary Significance

Josh Clark [10:05]:
"If I'd met a dinosaur in the street, I wouldn't have been more astonished." [09:50]

Coelacanths have been pivotal in understanding vertebrate evolution. Once thought to be a "missing link" between fish and tetrapods, genetic studies have refined their position:

• Sarcopterygians: Coelacanths belong to this group, linking them closely to lungfish and, by extension, to terrestrial vertebrates.
• Living Fossils: Although often termed "living fossils," recent genomic studies suggest that coelacanths have evolved, albeit at a slower rate compared to other species.

Chuck Bryant [15:23]:
"They have a slower rate of substitution." [15:58]
Research published in Nature highlights their reduced evolutionary rate, attributed to stable environmental conditions minimizing the need for rapid adaptation.

5. Current Status and Conservation

Josh Clark [35:18]:
"They have exclusively a small population... on the endangered species list." [35:18]

Today, coelacanths are critically endangered, with only two known species surviving:

• West Indian Ocean Coelacanth (Latimeria chalumnae): Primarily found around the Comoros Islands off the east coast of Africa.
• Indonesian Coelacanth (Latimeria menadoensis): Discovered in 1997, this species has a slightly different coloration and smaller size compared to its African counterpart.

Chuck Bryant [35:56]:
"There are possibly about 1,000 in Indonesia and far fewer off the west coast of Africa." [35:56]
Conservation efforts are paramount to prevent their extinction, as their unique lineage would be lost forever.

6. Reproduction and Behavior

Chuck Bryant [24:38]:
"They reproduce through ovoviviparity... gestation lasts three years." [24:00]

Coelacanths exhibit unique reproductive traits:

• Ovoviviparity: Females give birth to live young after eggs develop and hatch internally.
• Extended Gestation: A lengthy three-year period from egg to birth, during which the mother may inadvertently consume her offspring.
• Social Structure: Evidence suggests potential monogamous pairings, as indicated by studies of pregnant females bearing single fathers.

Josh Clark [25:09]:
"They have a longer gestation period than most fish." [25:09]
This extended reproductive cycle underscores their vulnerability, given the low population numbers.

7. Unique Adaptations and Behaviors

Chuck Bryant [20:00]:
"They live in the Twilight Zone... nocturnal hunters." [20:00]

Coelacanths inhabit deep-sea environments, typically residing between 500 to 800 feet in the ocean's Twilight Zone. Their nocturnal hunting tactics involve passive bycatch, relying on currents to bring prey within reach.

Josh Clark [22:22]:
"They have an electrosensory organ that detects electrical impulses." [22:22]
This adaptation allows them to locate prey in the dark, murky depths where visibility is minimal.

Josh Clark [22:55]:
"They swim nose down for up to two minutes, headstanding in place." [22:55]
Such behavior may be related to their hunting strategy, utilizing their rostral organ to sense prey.

8. Anecdotes and Lesser-Known Facts

Chuck Bryant [36:16]:
"A hematologist once wrote a coelacanth operetta titled 'Asila Kamp's Lament, or quintuplets at 50 fathoms can be Fun.'" [36:16]
Highlighting the cultural impact of coelacanths, the hosts share quirky stories, including a musical operetta inspired by these ancient fish.

Josh Clark [33:34]:
"Their brains occupy 1.5% of their skull... the rest is fat." [33:34]
A fascinating anatomical detail that sheds light on their unique physiology.

9. The Future of Coelacanths

Chuck Bryant [35:56]:
"Unless we revive them with some of their DNA, this order is gone." [35:56]
The extinction of coelacanths would mean the loss of an entire branch of vertebrate evolution. Efforts in genetic research and conservation are crucial to ensure their survival.

Josh Clark [36:00]:
"All of these coelacanths matter if there are only a few hundred left." [35:56]
Emphasizing the critical state of their populations and the importance of each individual in maintaining the species.

10. Conclusion and Listener Engagement

Towards the end of the episode, the hosts pivot to discussing other living fossils and engage with listener mail, sharing personal anecdotes and encouraging audience interaction. They blend scientific insights with humor, making complex topics accessible and entertaining.

Josh Clark [42:41]:
"If you want to know more about living fossils, like coelacanths or us. Right. You can type those words in the search bar@howstuffworks.com." [42:34]
Encouraging listeners to further explore the topic through their platform.

Notable Quotes:

• Chuck Bryant [09:50]:
  "If I'd met a dinosaur in the street, I wouldn't have been more astonished."

• Josh Clark [22:22]:
  "They have an electrosensory organ that detects electrical impulses."

• Chuck Bryant [35:56]:
  "Unless we revive them with some of their DNA, this order is gone."

Final Thoughts

"Selects: How Coelacanths Work" offers an in-depth look into one of the ocean's most mysterious survivors. Through engaging dialogue, historical anecdotes, and scientific exploration, Josh Clark and Chuck Bryant illuminate the fascinating world of coelacanths, underscoring their importance in both evolutionary biology and the urgency of their conservation.

For listeners eager to delve deeper, the episode provides a blend of education and entertainment, staying true to the essence of Stuff You Should Know.