Shelf Life 03: Six Ways To Prepare a Coelacanth
Shelf Life Episode 3 - Six Ways To Prepare a Coelacanth - Transcript
MELANIE STIASSNY (Curator of Fish at the American Museum of Natural History):
In 1962, the Museum gets a telegram from the Comorian archipelago...
"We have a coelacanth for you."
The coelacanth is like an icon of evolutionary biology— a living representative of a very ancient group of fishes that we thought had gone extinct maybe 65, 70 million years ago.
It would be like, you know, someone calls them up with a picture of a Tyrannosaurus, saying "This was running around the vegetable patch. You know, is it interesting?" Yeah, it was.
My name's Melanie Stiassny, and I'm one of the curators of fish here at the American Museum of Natural History.
So, we had a visiting researcher here at the Museum and he'd requested to dissect the coelacanth that we had. And to everyone's surprise, when it was opened up inside her we found five embryonic coelacanths, five pups. It was her that basically taught us that coelacanths give birth to live young.
They're so super cute.
The thing about the coelacanth is they're actually now very endangered. We can't just go out and get a coelacanth anymore. So, it was kind of a no-brainer that we were going to try and prepare them in as many ways as possible, to get as much data out of them.
How we're going to treat a specimen really depends on how many we've got, and what the scientific questions are.
If we just have one specimen, a particularly rare specimen, we would still take a tissue sample because that can be very non-invasive. We want to be able to have an archive of the DNA of the organisms that we're collecting.
And then the standard procedure would be to preserve, to fix it in formalin. The formalin infuses all of the tissues and it just stops any process of decay. And then we transfer them into ethanol.
And we know that this works because we have specimens that are hundreds of years old and they're absolutely fine.
But there are downsides to it. And particularly for fish, one of the downsides is the color goes. The pigments that give the fishes their iridescence and their beautiful colors, which are actually biologically really important, dissolve. They're gone.
But a collection is not just a jar. I mean, it really is all of the contextual information.
And obviously, when we're in the field, and we're making a collection of fishes, we try and take as many photographs as we can. Along with all of the notes about geographical coordinates, about what we caught it with, what the water quality was like, et cetera, et cetera, we have this record of what the fish looked like in life.
Skeletal specimens are really good for looking at big bits of anatomy. It's a very nice way of getting a three-dimensional representation, particularly a fish's skull.
To make a skeletal specimen we actually use the larvae of beetles, dermestid beetles. The little dermestid larvae nibble and nibble and nibble and it's a fantastic process, actually. You get this beautiful clean skeleton.
Cleared and stained specimens for fish are great because you just basically get this see-through anatomy.
RADFORD ARRINDELL (Senior Scientific Assistant in the Department of Ichthyology):
We clear and stain mostly the smaller things because that way we allow delicate elements to remain intact without destroying them through dissection.
My name is Radford Arrindell, and I'm a senior scientific assistant in the Department of Ichthyology.
The first step is to prepare the specimen by skinning and removing the eyes and the gill arches.
The second step is actually the bleaching of the specimen to remove whatever pigment remains within their tissues.
The third step would be to dehydrate the specimen in ethyl alcohol—like squeezing out a sponge—so that their structures more readily pick up the dye.
The next step involves placing it in the blue stain. Blue is for the cartilage. Then it's placed in the enzyme solution to begin the clearing process.
After it's partially cleared, where you can begin to see some of the structures, you then begin the red stain The red stain goes to the bones, and once it's been stained all the way through you complete the clearing.
We then put it into glycerin where it will always keep the specimens moist and support them. Because they are actually kind of floppy and fragile.
With a serially sectioned specimen, basically, we're making lots of slices. And then each of those slices —which are really, really thin —can then be stained differentially. So, under a microscope, you can actually really see that very fine cellular detail. In many ways, it's the best thing you can have.
Now, with all of the new technologies we have, these collections become even more important, even more rich.
I mean, when I first started, CT scanning – that was not something in our wildest dreams that you thought you could afford to CT scan a fish. But now we can. So, we can look in fabulous minute detail at anatomical structures. Amazing.
The critical and key thing is to have these specimens preserved and conserved for all time. Here at the Museum, we have a collection of you know, over two million fish specimens. They go back 130 years. We could never reproduce what we've got here. Because the world has changed.
So, this is almost like a time capsule. Everything you read about, you know, the impacts of climate change, how organisms' distributions are changing, all of these things— it's based on specimens like these.
It would be like someone calls up with a picture of a Tyrannosaurus saying, “This was running around the vegetable patch. Is it interesting?” Yeah, it was.
-Melanie L. J. Stiassny, Curator, Division of Vertebrate Zoology
Among the sharks and seaweed caught in the nets of a South African trawler on December 22, 1938, there lay a large blue fish, dappled with white spots. Its armor-like scales and lobed fins recalled a group of fishes that scientists thought had died out 70 million years ago. As it turned out, reports of the coelacanth’s extinction had been greatly exaggerated.
The fish’s rediscovery caused a stir around the globe. “Loch Ness Outdone,” proclaimed the Aukland Star. A curator here at the Museum called it “one of the events of a lifetime.” More than 75 years later, the coelacanth continues to be one of the world’s most intriguing species. The Museum’s Ichthyology and Paleontology collections house several specimens of Latimeria chalumnae (the West Indian Ocean coelacanth) and its ancient fossil relatives.
Paleontological Vanishing Act
For a fish once considered a possible “missing link” between aquatic and land vertebrates, it’s perhaps ironic that the coelacanth was first described in 1839 by Louis Agassiz—an influential biologist who rejected Darwinian evolution. (Darwin once wrote: “How very singular it is that so eminently clever a man, with such immense knowledge on many branches of Natural History, should write such wonderful stuff & bosh as he does.”) Agassiz was, however, a talented paleontologist and described Coelacanthus from a fossilized tail.
The first coelacanths appear in the fossil record as far back as 415-360 million years ago, when they shared the ancient oceans with ancestors of modern sharks, rays, and other fishes. As new species evolved, ancient coelacanths inhabited both marine and freshwater environments. The biggest coelacanths—like the massive Mawsonia, over 5 meters long—lived 110 million years ago in the Cretaceous lakes and rivers of South America and West Africa, which were then a single continent.
Paleontology Curator John Maisey discovered a slightly smaller coelacanth contemporary of Mawsonia and named it Axelrodichthys. “Axelrodichthys and Mawsonia were similar to living coelacanths in many ways,” says Maisey. “For example, the Cretaceous coelacanths had a diamond-shaped tail and a spiny first dorsal fin on the back, but unlike the modern species, had highly ornamented bones on their heads and no teeth.”
The coelacanths hang in the fossil record through the time of the dinosaurs, then disappear about 70 million years ago, never returning to shallow seas, lakes, or rivers. This vanishing act may have to do with their environment and the surrounding geography. The steep undersea slopes inhabited by modern coelacanths don’t offer the best conditions for fossilization, and active plate movement in the region may destroy any fossils that happen to form.
It Came From the Deep...
Almost a hundred years after Agassiz first described this ancient group of fishes, coelacanths splashed into the modern era. The specimen pulled from the trawling nets of a South African fishing boat in 1938 was discovered by Marjorie Courtenay-Latimer, the curator of the East London Museum in South Africa. Courtenay-Latimer had taken over the Museum seven years earlier, at the age of 24, and while she’d never had formal scientific training she was a perceptive self-taught naturalist. The scales, head plates, and fin formation of this strange fish reminded her of ancient specimens, and she decided to contact J. L. B. Smith, a lecturer and ichthyologist at Rhodes University.
Since this fishy drama unfolded around the Christmas holidays, Smith proved difficult to track down. Meanwhile, it was summertime in South Africa, and the heat was taking its toll on the specimen. With the help of an asisstant, Courtenay-Latimer pushed the coelacanth carcass through sweltering East London streets in search of a cool storage spot. Turned down by the local mortuary and a food refrigeration facility, they ended up at a taxidermist’s, where they wrapped the fish in formalin-soaked newspapers and hoped for the best.
When Courtenay-Latimer finally received a reply from Smith 11 days later, it was too late to save the soft parts of the fish. But the skeleton and skin remained. Based on Courtenay-Latimer’s description, Smith thought this specimen was indeed the fish that had long been considered extinct. It wasn’t until February 16, 1939, that he finally reached East London to confirm his suspicions. “Although I had come prepared,” Smith later wrote, “that first sight hit me like a white-hot blast and made me feel shaky and queer.... Yes, there was not a shadow of a doubt, scale by scale, bone by bone, fin by fin, it was a true Coelacanth.”
Smith and his wife Margaret spent the next 14 years searching for another specimen. With the support of Courtenay-Latimer, they printed and distributed thousands of leaflets offering a reward for an intact fish. “Look carefully at this fish,” the poster proclaimed in English and Portuguese. “It may bring you good fortune. Note the peculiar double tail, and the fins....every one is valuable for scientific purposes and you will be well paid.”
Monsieur le Professeur
The reward was at last claimed in 1952, by Ahamadi Abdallah, a fisherman from the Comoro Islands. J. L. B. Smith convinced the South African government to sponsor a plane for the coelacanth’s retrieval and returned with the specimen to great fanfare. During a national radio broadcast, he recounted opening the crate and weeping as he saw the big fish before him—and broke into tears anew. Again, the coelacanth made headlines around the world, and letters poured in from well-wishers. One ichthyologist wrote to Smith from the U.S.: “Now I can die happy, for I have lived to see the great American public excited about fish."
Over the next decade, several other coelacanth specimens were collected in the Comoran archipelago, all of which were shipped to French researchers. (The Comoros were a colony of France until 1975.) Dr. Jacques Millot led a project that would span more than 20 years, culminating in a three-volume monograph on coelacanth anatomy in 1978.
Now I can die happy, for I have lived to see the great American public excited about fish.
Despite the worldwide fish fever, no coelacanth specimen had yet made it to the Western Hemisphere. Then in 1962, Bobb Schaeffer, a paleontology curator at the American Museum of Natural History, received an urgent letter from J. L. B. Smith. Smith had gotten word from a French doctor in the Comoros that a coelacanth specimen was available.
“Monsieur le Professeur,” the French physician Dr. Georges Garrouste wrote to Schaeffer, [the coelacanth is] “a very beautiful specimen— female, I think—and certainly the most beautiful I have ever seen.” A flurry of letters and telegrams crossed the Atlantic, as the prospect of adding a coelacanth to the Museum’s collection began to take shape. Schaeffer wanted assurance that the fish was well preserved. He also wanted to make sure that the Museum’s acquisition would be acceptable to Dr. Millot, the French scientist who had not yet published his coelacanth research. With confirmation of the specimen’s good condition and Millot’s encouragement, soon-to-be catalog number 32949 arrived at the Museum in April, 1962—the Western Hemisphere’s very first coelacanth.
It’s a girl! …and a boy, and a girl, and a girl, and another boy.
For the next 13 years, 32949 sat in a tank in the Ichthyology Department—admired, but largely untouched. That would all change with a request from Dr. Charles Rand, a Long Island hematologist who was interested in obtaining tissue samples for comparative research. After some careful consideration, the Museum’s scientists agreed to go into the belly of the fish. On the morning of September 10, 1975, Rand, along with Bobb Schaeffer and Ichthyology Curators James Atz and C. Lavett Smith, began dissecting the coelacanth—and made an astonishing discovery.
Elbows-deep in fish innards, Smith and Rand found three embryonic coelacanths—1-foot-long versions of their mother, with yolk sacs still attached. Two more embryos were found in subsequent dissection, and the Museum’s population of coelacanths sextupled in short order. Researchers had long debated whether the fish laid eggs or gave birth to live young, and the 1975 dissection finally put the reproductive mystery to rest.
The hematologist, Dr. Rand, was so inspired by the ichthyological revelation that he penned a libretto for a short operetta, A Coelacanth’s Lament, or Quintuplets At 50 Fathoms Can Be Fun, set to Gilbert and Sullivan tunes. Here’s a selection from Act One, to be sung to the melody of The Mikado’s “Tit Willow:”
(Disclaimer: The Museum takes no responsibility for the quality of rhyme.)
The specimens collected since the species’ discovery in 1938 have been thoroughly studied, yet in some ways the coelacanth remains an enigmatic animal. A second species was discovered in Indonesia in 1997, and scientists are slowly learning more about the fish’s range and biology. Latimeria chalumnae, the West Indian Ocean coelacanth, was listed as an endangered species by CITES in 2000, so preserving existing specimens in museums and institutional collections around the world for future study is more important than ever.
As a fish first known from the fossil record, the coelacanth has a well-studied skeleton. “There are so many extraordinary features about the coelacanth,” says Axelrod Research Curator Melanie L. J. Stiassny, “but one of the most remarkable is that it’s the only living vertebrate with what’s called an intercranial joint. The back half of the skull is actually physically separated from the front half of the skull, enabling the coelacanth to really get a big gape. It’s like if your dog was able to lift its snout up, and it hinged on the back of its skull.”
The lobed, limb-like fins of the coelacanth are also highly distinctive features, part of the reason the fish was an early candidate for a “missing link” between water and land vertebrates. Once coelacanths were finally observed in the wild in 1987, researchers learned that their fin movement is patterned in the same sequence as the gait of a quadruped. However, they do not use their fins to crawl along the seafloor, as J. L. B. Smith had expected.
Another anatomical feature that’s been illuminated by living coelacanth behavior is the animal’s rostral organ—a large cavity above the nasal sacs, which is connected to three openings on the head and filled with a jelly-like substance. This feature is unique to coelacanths among all living vertebrates and likely functions as a kind of electro-receptor, detecting low-frequency signals given off by potential prey. Coelacanths have often been seen performing a sort of headstand, holding their snouts (and therefore rostral organs) close to the seabed. Researchers noticed they could spur this behavior by generating small currents in the nearby water.
So, is the coelacanth our ancestor? The short answer is no. Its full genome was sequenced in 2013, and the results, along with much study of coelacanth anatomy and the fossil record, suggest that the modern lungfish is a closer relative to land vertebrates. But questions remain as to its range (there are tantalizing hints of coelacanths in the Atlantic), its reproduction (how do coelacanths mate?), and its population size, among many others. But whether or not we can call the coelacanth a great-grandma, it remains a fascinating fish.