Friday, May 27, 2011

The man who swims with coelacanths

From Arkive

From Wired

More than seven decades later, the words have the same urgency as when they rolled off
Marjorie Courtinay-Latimer’s telegraph machine and into history:

Courtinay-Latimer was the young curator of a natural history museum on South Africa’s east coast.
The message came from
J.L.B. Smith, an icthyologist to whom she’d turned when, shortly before Christmas in 1938, local fishermen brought her a fish unlike any they’d ever seen.

Caught at a depth of 240 feet, it was five feet long, covered in bony scales and had fins reminiscent of legs.
Courtinay-Latimer immediately sent a sketch to Smith, who thought it looked like a
There was just one catch:
Coelacanths were extinct, and had been for 70 million years.

The sketch sent by Marjorie Courtinay-Latimer to J.L.B. Smith.
South African Institute for Aquatic Biodiversity

Smith’s famous cable came too late, as Courtinay-Latimer didn’t have an aquarium large enough to preserve the fish.
But even as they despaired, it was just weeks before another arrived.
Far from being extinct,
coelacanths were actually caught with some regularity by native fishermen of the Comoros Islands, on whose rocky undersea slopes they’d lived since swimming with dinosaurs.

The coelacanths of the Comoros Islands, along with
another population discovered in Indonesia, are now celebrities of the animal kingdom, and nobody has spent more time with them than Hans Fricke.
In 1986, the German explorer and then-freelance photographer convinced a magazine editor to send him and a submarine to the Comoros.
Since then he’s led more than 400 dives, helping to produce much of what is now known about coelacanths.

After the publication of his latest work, published in Marine Biology and entitled “The population biology of the
living coelacanth studied over 21 years,” talked to Fricke about his time with the mysterious, magnificent creatures. How did your interest in coelacanths begin?
Hans Fricke: When I was young, I read the book by J.L.B. Smith, Old Four Legs.
I was a keen skin diver, because I was 11, and I said, ‘Good friend, this fish you will see once in your life.’
In 1975, I joined an expedition of the Royal Society to Aldabra Atoll, and then I went to the Comoros, where I did some very stupid, very daring scuba dives to down over 300 feet.
But I found nothing.
I said to my wife, “Next time I come here, I’m coming with a submarine.”
I said it as a bit of a joke, but the next time I came to the Comoros, in 1986, I came with a submarine. Can you describe that first submersible?
Fricke: It was made by two Czechoslovakian engineers in Switzerland.
We made the first trials in Lake Constance, then I smuggled the submersible over the Swiss-German border, because I would have had to pay customs.
It was covered in a sheet and looked like an American Sherman tank.
The border policeman asked me, “Friend, what is below this sheet?” I said, “A submarine.”
He said, “No.” I said, “Yes it is. I was in the lake diving,” and told him some fish stories.
He found it really interesting, and forgot to ask the crucial question: if I’d paid customs. When did you first find a coelacanth?
Fricke: We tried hard to find the fish, but we didn’t look carefully enough, we didn’t know about its behavior.
The fish are nocturnal, and hide during the day.
I had to fly back home to Munich, and two of my friends continued for five more days.
They found it.
Of course my friends immediately called my family.
I had a stopover in Paris, called my family, and my little son said, “How is the fish?” And I said, “Which fish?”
He said, “The coelacanth!”
This was a great moment.
I had tears in my eyes.
I went back a couple weeks later, and on the first dive we found them What is it like to see one?
Fricke: You immediately grasp that something is fishy with this fish.
It is not a normal fish.
Their movements are extremely slow; it has something like a mute character.
I had the feeling I had an amphibian in front of me, because of the movements of the fins.
I discovered a very funny, tetrapod-like movement of the fins, a kind of cross-step that they do.
If you were to cut a coelacanth across the middle, you’d see that it’s almost an ellipse.
If one make a downbeat with its right pectoral, the beast turns.
To counter this, it has to make a counter-downbeat on the far left side.
This produces the tetrapodic cross-step.
It’s a normal thing for an animal on land, but we’re talking about a fish.
This could be a pre-adaptation for the step to land.
They move so slowly.
J.L.B. Smith said this gives you impression they crawl on their fins at the bottom of the sea, but they don’t.
They don’t even touch with their fins. If they move so slowly, how do they capture prey?
Fricke: They have a giant electroreceptor in their head, called the rostral organ.
They perceive the electric field which a swimming object in salt water produces.
Lava fields have reduced magnetic anomalies, and if you swim as a fish in this field, of course you produce in your own body an electric field which you could measure.
It is very likely the fish orientates himself via detecting magnetic anomalies in seawater.
It’s amazing — it’s a landscape like Hell, like the lava fields in Hawaii, and they go into this field and orient themselves precisely and fast. How do juveniles find homes?
Fricke: We never found a juvenile.
We are very puzzled by the fact that we see only sub-adults.
That means they must live somewhere else, and we don’t know where.
We had once a pregnant female radio-marked with a pinger, and she did something extraordinary: She went down to 2,300 feet and remained for the day at that depth.
Something must have happened with her.
I believe she gave birth, but I could not follow her and see if her abdomen was still swollen and prove it.
But it makes sense that they live down there.
If a juvenile swam in front of an adult, they’d eat it.
‘They need about 12 grams of food a day. This is probably the secret of their evolutionary success.’ It takes three years for an embryo to develop. Why so long?
Fricke: They have the slowest metabolic rate known among vertebrates.
We made a calculation that a coelacanth needs, for its resting metabolism, 3.8 milliliters of oxygen per kilogram per hour.
A tuna needs 400 milliliters.
Because coelacanths are always burning at a low metabolic flame, they are able to live in low-energy areas, where there isn’t much food.
The lava fields are a low-product habitat.
They need about 12 grams of food a day.
This is probably the secret of their evolutionary success.
They live where hyperactive fish cannot survive. Is climate change going to be a problem?
Fricke:With each water temperature increase of 10 degrees Fahrenheit, metabolic requirements are doubled, so they have to live under a special temperature regimen.
They live in areas with a temperature of 59 to 64 degrees Fahrenheit.
It’s there that their hemoglobin has the best capacity for oxygen.
They can’t live anywhere else.
They also need caves.
If there are no caves, the fish can’t survive.

We did a study with [Microsoft co-founder]
Paul Allen’s fantastic equipment, which let us dive very deep.
And the sad story in the Comoros is, the volcano is eroded below 650 feet.
There’s no place to hide there.
In 1991, when there was an El Niño happening, we found 40 percent fewer coelacanths in our area.
At 720 feet, it was 77 degrees Fahrenheit.
The fish would be in respirational stress.
With climate change, if the water temperature increases, they would have to go deeper, but there are no caves.
And this would be the end of the Comoros population.

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