Sunday, 23 June 2013

Coelacanth


It's the world's most famous living fossil! Or is it? A living fossil, I mean. Because the Coalacanth is so ridiculously famous that whatever it is, it's probably the most famous one.

A guy from the future just gave me his time machine! He says it works quite well most of the time, and people usually don't die when they use it! And we'll probably come back with almost all our limbs, at least 40% of our face and only moderate burns. Sounds good to me! So I thought we could go back in time.


We won't go back millions of years to find a real, live Coelacanth... we'd only end up stepping on a butterfly and causing the world's languages to change slightly and all the world leaders would be different. That'd just be annoying.

Instead, let's go to 1836. Charles Darwin is off on his round-the-world adventure on the HMS Beagle and he will return this year. A young journalist called Charles Dickens is taking his first steps in fiction, publishing a novel called The Pickwick Papers as a monthly serial. He'll start work on Oliver Twist at the end of the year.

Image: Alberto Fernandez Fernandez
Adelaide in Australia has just been founded and will one day become the fifth largest city in that country. Also, it's a great year for massacres in America! Texas is in revolt against its Mexican overlords and for the next ten years will be known as the Republic of Texas. Davy Crockett, King of the Wild Frontier, will die in the Battle of the Alamo this year and months later, as 1836 draws to a close, Spain will finally recognize Mexican independence. You win some, you lose some.

So it's a fascinating year, full of opportunity and adventure for the scientist, the writer and the idealist. And if you just want to try out killing people, you can do that, too. But we're not going to any of those exciting, dangerous places. We're going to Switzerland.

Image: Jim O'Donnell
The Swiss had a rough time under Napoleon, who's only been dead 15 years, but in 1821 Switzerland regained full independence and was recognised as a permanently neutral state. Which is a bit weird. They're a few years away from political violence and civil war, but in the meantime, we're off to pick up Louis Agassiz's latest tome.

Leafing through the pages of the second volume of Recherches sur les poissons fossiles by celebrated, Swiss paleontologist Louis Agassiz, we find a fish. Actually we find lots of fossil fish, also known as les poissons fossiles. The book title is not imaginative.

Coelacanthus granulatus in the the book by Louis Agassiz
It's the first description of Coelacanthus granulatus. We didn't really need to go all the way over here to see it since the whole book is freely available on the internet, but when a man materialises in a flash of light right before your eyes, screams about how "they're coming! They're coming for me!" and begs you to take his time machine and then rushes off saying "run! They'll be after you now!", well... how can you not use it?

Image: Ghedoghedo
C. granulatus fossil
The name Coelacanth means "hollow spine", referring to the hollow rays of the tail fin. Over the next century many more fossils of C. granulatus and numerous relatives will be discovered, always in rocks between 400 and 65 million years old. It will seem clear that Coelacanthus and everything like it was wiped out along with the dinosaurs.

That will change in 1938, when a new picture of the Ceolacanth will emerge.

World's first sketch of a living Coelacanth, by Marjorie Courtenay-Latimer
Marjorie Courtenay-Latimer was a museum curator in East London, South Africa (gotta love place names with their own directions). She was always on the lookout for interesting things to add to her collection and, to that end, had struck up a friendship with a local angler called Captain Hendrick Goosen. Three days before Christmas, 1938, he had a few specimens he hoped she would find interesting.

There might have been loads of interesting fish staring up at her that day, but one of them was 1.5 m (5 ft) long and looked prehistoric and weird so it duly monopolised her attention. From there, everything becomes a hilarious farce.

She and her giant, dead fish took a taxi back to the museum. The day was hot and she needed to preserve the thing, so when the morgue refused to accept a fish no matter how interesting it was, and when it wouldn't fit in her bath, she drenched some clothes in formalin and wrapped them around the corpse, instead.

The stuffed specimen. Neither living nor fossil
Alas, the internal organs, interesting as they may be, were rotting. Good thing she didn't keep it in her bath... So on Boxing Day a local taxidermist skinned and stuffed the body, dumping those fascinating innards in the bin where they would never be seen again.

Meanwhile Courtenay-Latimer had sent a letter and "good enough" sketch to J. L. B. Smith, a university lecturer who had offered his expertise in identifying fish for her collection. He probably dropped his pipe into his corn flakes, because he knew what he was looking at. At long last, on 3rd January, 1939, Courtenay-Latimer received his reply by telegram:

MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED

I can almost see her rolling her eyes and sighing, "you don't say..."

Her efforts were rewarded with the naming of the fish, Latimeria chalumnae, named after herself and the river near to which it was found.

J. L. B. Smith lovingly strokes a Coelacanth, 1952
It would be another 14 years before another living Coelacanth would be found. This time it was fished up from deep waters off the tiny Comoros Islands near Madagascar, and the fishermen were keen to collect a £100 reward offered by J. L. B. Smith for a new specimen. Annoyingly enough, the local fishermen knew the Coelacanth well. They called it the Kombessa. It wasn't good eating, but the tough scales had their uses.

A lot more is known about these Coelacanths today. Not least that there is another species near Indonesia that was discovered in 1997. They can reach 1.8 metres (6 feet) long and live in deep, dark waters where they conserve energy by mostly not doing anything at all.


Video: arkive

They have a whole host of interesting and unique characteristics:
  • Firstly, those extraordinary lobed fins! Coelacanths have two dorsal fins, one attached directly to the body as in other fish. All the others come at the end of fleshy stalks that contain the same kind of bone structure as found in tetrapod limbs. They are extremely manoeuvrable and allow Coelacanths to swim head down, searching for fish to eat from the seabed.
  • A unique organ up their nose detects the electrical impulses given off by prey. No other creature has it, and along with their sensitive eyes, it allows them to find prey in their gloomy habitat.
  • Now it's time to snatch their prey, and they have another feature unseen in any other living animal to help out. It's called an intracranial joint. It allows the front half of the head to lift up so the Coelacanth's mouth can open much more widely than it looks like it should.
  • Then there are the tough, rough scales quite unlike those of most fish. They serve as a kind of armour so that the Coelacanth can spend lots of time relaxing in the nooks and niches of craggy rock formations without fear of injury.

Video: Saranaser

Looking a little deeper at those interesting organs, we find more:
  • A kind of swim bladder full of oil and fat. Most fish fill this thing with air, but that would be crushed in the pressure of the Coelacanth's deep abode.
  • A notochord! Most vertebrates turn this into the backbone during embryonic development, but in common with some fish like the Sturgeon, Coelacanths retain the flexible notochord for life.
  • A tiny brain! Coelacanths are fat-heads. Their brains takes up just 1.5% of their braincase, all the rest is fat. This is incredibly tiny for such a massive animal, but this fish of very little brain seems to be doing quite well on it!
  • Oh, yeh... and they still have those hollow spines that got them their name in the first place. I'm almost sorry about that; it would be hilarious if they were named after the one thing they didn't have any more!


The Coelacanth is a nocturnal lurker (like some of you :P) who sits in the darkness, happy to drift slowly on the currents and use their fins primarily to point their face in whatever direction they want. When they see prey, a swish of the tail allows them to pounce with great speed.

The day is spent resting among the complicated architecture of volcanic rock. Coelacanths are quite gregarious, sometimes hanging out together in crowded caves. They don't like to physically touch, though. Sounds like the start of a gothic love story! Therefore they must eventually touch... quite a lot. You know...

After which the female will be pregnant for over a year! She produces up to 25 eggs but doesn't lay them. Instead, they hatch within her body and grow to about 30 cm (a foot) long before mother gives birth and the young pups see the light of day dark of sea. It's a reproduction strategy more akin to that employed by many sharks, rather than the "thousands of tiny eggs" other bony fish use.


So the Coelacanrh is certainly a strange fish richly endowed with peculiarities and archaic characteristics, but is it really a living fossil? Certainly it's living (famously so!), but is it fossil?

Unfortunately, "living fossil" isn't a particularly well defined term. The two modern Coelacanths were not around hundreds of millions of years ago, unlike certain Tadpole Shrimp, for example. They aren't even placed in the same genus as any ancient Coelacanth. But their evolution does seem to be very slow, and they are the last living example of a once diverse slice of life that is now otherwise completely gone.

Today, Coelacanths are one of the three subclasses placed in the class Sarcopterygii, which means "flesh fin" because they are the lobe-finned fishes. The other two are the lungfish, which are yet more fishes with lobed fins, and the last one contains the tetrapods, like you and me!


Video: NatGeoWild

The story of the Coelacanth is a fascinating one. It makes one wonder what other strange beasts may lurk in far flung locations, waiting to be discovered, only for it to turn out that the locals knew about it the whole time and labelled it "inedible".

But it also makes me wonder what ancient creatures are completely lost to us through the vagaries of the fossilisation process. Coelacanths were alive somewhere for 65 million years and we don't have a single fossil from that entire period! Where were they? What else was hanging around in this place so unforgiving to fossils?

At least it's nice to know that the Coelacanth would see me as an incredibly weird-looking fish. That's heartening.

2 comments:

TexWisGirl said...

they've done quite well for 'fat heads', being around so long. the being pregnant for a year and all is kind of icky.

Joseph Jameson-Gould said...

Yes! They are very impressive beasts!

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