Is This the Mother of All Animals?

[MUSIC]

[A split screen depicts a chimpanzee on the left, and a hermit crab on the right.]

ROB DESALLE (Curator, Division of Invertebrate Zoology): Look around you and look at all the animals, 

[A new split screen has a clownfish and anemone on the left, and a microscopic tardigrade (water bear) on the right.]

DESALLE: –and plant life we have on the planet. 

[DeSalle appears on screen, speaking to the camera.]

DESALLE: One of the mysteries of science is, how do we get all that diversity? 

[A single-celled organism squiggles around on screen.]

DESALLE: And one of the ways of understanding–

[A nematode worm wriggles on screen.]

DESALLE: –that is through understanding how–

[A jellyfish pulsates on a deep blue background.]

DESALLE: –organisms develop to–

[Three dolphins race and jump through the water.]

DESALLE: –multicellular cellular kinds of animals. 

[DeSalle reappears on screen.]

DESALLE: You can't really do any of this developmental biology without the primordial organism. 

[An amorphous white microscopic blob moves on a dark background.]

DESALLE: Placozoa are the simplest anatomical animal on the planet, 

[The screen is filled with several of these white microscopic blobs, placozoa.]

DESALLE: and they may very well represent the primordial animal type.

[The American Museum of Natural History logo appears over footage of placozoa. A petri dish appears with several white blobs in it, visible to the naked eye though still very small. Text appears: The Worldwide Search for Placozoa, Constantine S. Niarchos Expedition]

DESALLE: The animal that we work on is an animal called–

[Another placozoa appears on the screen, microscopic on a black background. Text appears, pointing to the animal: Trichoplax adhaerens, phylum Placozoa.]

DESALLE: –Trichoplax. It's in the phylum Placozoa. And, they were first observed–

[An aquarium with fish swimming around.]

DESALLE: –in the 1800s from aquaria–

[In one corner of the same aquarium, there are several collecting microscope slides.]

DESALLE: –in Germany. 

[DeSalle reappears on screen. Text appears: Rob DeSalle, Curator, Division of Invertebrate Zoology.]

DESALLE: There weren't any lineages of this animal caught from nature until about two decades ago. My colleague Bernd Schierwater, who is at the University of Hannover in Germany, is–

[DeSalle sits in a conference room with Bernd Schierwater, discussing things together on their laptops.]

DESALLE: –I think, the world's expert in Placozoan biology. He got me interested in these animals about 25 years ago.

[Schierwater appears on screen, standing on a rocky beach with [WIND] occasionally hitting the microphone. He speaks to the camera. Text appears: Bernd Schierwater, Professor, University of Veterinary Medicine at Hannover.]

BERND SCHIERWATER (Professor, University of Veterinary Medicine at Hannover): Placozoan, the word says‚ “placo–” like “plate”, “–zoan” like “animal”. So it's a plate animal. 

[Closeup of the water lapping the rocky shore of the Mediterranean.]

SCHIERWATER: All tropical subtropical waters– 

[Schierwater walks along the rocky shore and into the surf.]

SCHIERWATER: –should have placozoans in them. 

[Underwater, hands use a pocket knife to put algae and seaweed samples into a plastic sampling tube.]

SCHIERWATER: They feed on algae. They are so simple, so easy, 

[A white blobby placozoan appears on screen.]

SCHIERWATER: –so primitive, that you could think–

[The screen splits to show the placozoan on the left, and a single-celled amoeba on the right. Text appears next to the amoeba: Protist, single-celled.]

SCHIERWATER: –they are protists. But they have four different cell types. 

[Text appears next to the placozoan: Metazoan (animal), multicellular.]

SCHIERWATER: And that makes them a metazoan. But the placozoans–

[Schierwater reappears on screen.]

SCHIERWATER: –really look very much like the mother of all metazoan animals.

[A placozoan floats through a microscope viewfinder.]

DESALLE: When I first started working with Bernd it was a single species, 

[A circle draws itself around the placozoan and the background outside the circle fades. A bracket above the circle appears, indicating a species. Above that bracket appears another bracket, labelled “Phylum Placozoa”.]

DESALLE: –just one species in the phylum. 

[The species bracket and placozoa circle fade away.]

DESALLE: Today we know that there are–

[Beneath the phylum bracket, two new brackets appear labelled “Class” and two different icons of a placozoa appear, one beneath each bracket. One of the placozoa is circular and the other appears twiggy and branching.]

DESALLE: –at least two classes and–

[Below the brackets for class appear three new brackets for Order. Three differently colored circles appear with icons for placozoa, though the placozoa themselves appear quite similar.]

DESALLE: –probably three orders of Placozoa–

[Five brackets for Family appear below the order brackets, with new and differently colored icons for different placozoa families, then yet one more bracket with many many icons of placozoa appears below the family bracket, titled “Genus & Species”.]

DESALLE: –and numerous families and tons of genera. The reason that we only started to see that there were different species out there–

[DeSalle reappears on screen.]

DESALLE: –is that we were able to look at their DNA. If you look at these things under a microscope, they all look alike. The goal of, of this project is to put all of these specimens that we're collecting from really interesting parts of the world–

[Different petri dishes appear, labelled “Panama,” “Cuba,” “Madeira.”]

DESALLE: –into that kind of system that allows us to say something–

[Several videos of placozoa under the microscope appear.]

DESALLE: –about the relatedness of these things.

[Schierwater appears on screen, speaking to the camera.]

SCHIERWATER: We are right now in the- [COUGH] someplace in the Mediterranean. 

[Beachgoers walk on the sand and in the water in the Mediterranean.]

SCHIERWATER: The Mediterranean Sea is a great place for placozoans to live. 

[Students assemble snorkeling fins and equipment on the beach, getting ready to ride bicycles to a new collecting location.]

SCHIERWATER: We have been collecting here–

[Students snorkel while picking up rocks and shells from the rocky sea floor.]

SCHIERWATER: –successfully for many years. This is one place where we can do collecting–

[Schierwater stands knee-deep in water near the shore, talking to his students in the water snorkelling.] 

SCHIERWATER: –by just walking into the water and also by snorkeling–

[Two scuba divers look on the rocky shore for shells.] 

SCHIERWATER: –and also by scuba diving. 

[A student snorkels to pick up rocks and puts them in a white canteen-like sampling jar with water.]

SCHIERWATER: Take a rock, we take a shell, we take anything that's a hard substrate–

[Several of these containers are lined up on a table, labelled with their sampling location.]

SCHIERWATER: –and put it into water, bring it to our lab–

[Two students sit at a table outside, with containers and a portable microscope. They look at and take notes on the rocks under the microscope.]

SCHIERWATER: –or bring it to the cabin here and put it under a microscope and look for placozoans.

[Schierwater reappears on screen, speaking to the camera.]

SCHIERWATER: Collecting is the fun part. [LAUGHTER] You get to enjoy the sun. You get to enjoy the water. Then comes the hard part.

[A yellow house in a field appears on screen. Text reads: Hannover, Germany. A research assistant stands in front of several glass tanks of rocks, and places microscope slides into them one by one.]

DESALLE: The samples, once they're taken, 

[Another view of one of the glass tanks, with a labelled white sampling container next to it.]

DESALLE: –they're sent back to the lab in Hanover. 

[A student carries one of the glass tanks of algae-covered rocks to a microscope and places it down to look at it.]

DESALLE: They're examined by an expert.

SCHIERWATER: The trick is, they are kind of transparent, 

[Schierwater appears on screen in the same laboratory, sitting in front of the microscope and describing what he is doing to the camera.]

SCHIERWATER: –but if you think you found one, you have to watch it to see if–

[An algae-covered rock under the microscope.]

SCHIERWATER: –the shape changes. If we get lucky–

[Tiny placozoans swim around in a petri dish, barely visible to the eye.]

SCHIERWATER: –we find new placozoans on the rocks–

[Schierwater stands in a different part of the laboratory, next to many rows of petri dishes.]

SCHIERWATER: –well then we try to isolate them. Once we’ve isolated a placozoan we try to grow it. 

[Closeup of rows and rows of petri dishes.]

SCHIERWATER: And some of them we can culture well, some of them are difficult. 

[Schierwater continues his tour of the laboratory by walking over to a different row of petri dishes.]

SCHIERWATER: These are older cultures… so this is a clone we got in the sixties, so some 60 years ago. 

[A researcher pulls samples from a petri dish while looking through a microscope. Placozoans appear under a microscope.]

SCHIERWATER: And it grows just perfectly fine. Even if we should not find anything within the next two or three weeks, 

[Schierwater appears back on screen, gesturing to the glass tanks in the original area of the lab.]

SCHIERWATER: –we keep the sample anyway. We put it in a bigger tank, we aerate it and make sure there’s always enough oxygen. 

[A lab assistant uses a pipette to put red algae into a petri dish.]

SCHIERWATER: We add actually a little bit of algae, some food to it, 

[Hands lift up a glass tank with rocks and sand in it, and add a water line label with marker on the outside.]

SCHIERWATER: –and we usually can keep the samples alive for a year or even longer.

[DeSalle reappears on screen, speaking to the camera.]

DESALLE: You want a lot of material to be able to work on, and these are tiny, tiny little animals. 

[DeSalle and Schierwater confer over their laptops in a conference room.]

DESALLE: The DNA is used to sequence, and then we compare the genomes of all the animals that we have in our database. 

[Insets of a thermometer and swirling ocean currents appear over an illustrated world map. 

DESALLE: We've computer modeled the distribution of these animals based on their preference for temperature, current speed and things like that. 

[The inset footage disappears and 10 blue markers appear across the continents—some in North America, South America, Europe, Africa, Asia, and Australia. 

DESALLE: And we've targeted, maybe ten different places on the planet where we're pretty sure we can get more animals. 

[Red markers also pop up on the map, indicating sites across the different continents where placozoa have been found in the past.]

DESALLE: And these ten places are different from the many places that they've been found before. 

[DeSalle reappears on screen, speaking to the camera.]

DESALLE: We're almost positive that we're going to find new species. 

[Group of students outdoors at dusk look through microscope.] 

DESALLE: You may not only discover a new species, you may discover a new genus, or you may even discover a new family. 

[DeSalle reappears on screen, speaking to the camera.]

DESALLE: Or, if you're lucky enough, you might find a new order or a class, which is something that's not done very much anymore in animal biology.

[Blobby, white placozoans move on a dark background.]

SCHIERWATER: Trichoplax and placozoans in general are great model systems, as I said, for evolutionary biology. 

[Schierwater reappears on screen, speaking to the camera.]

SCHIERWATER: They are great for understanding invertebrate zoology. They are probably bioindicator systems to tell us about the quality of ocean waters.

[Close up of a person’s hands moving around a petri dish under a microscope and using a pipette.]

DESALLE: They’re kind of an anatomical enigma that we need to figure out. 

[DeSalle reappears on screen, speaking to the camera.]

DESALLE: Trichoplax has all of the genes for a nervous system, but they don't have a nervous system. They have all the genes for musculature, but they don't have muscles. 

[Close-up of glass dish where placozoans are visible inside as small white specks. Other views of amorphous placozoans oozing around under a microscope.]

DESALLE: Believe it or not, these little pancakes have an immune system that's quite similar to our innate immune system. It is now useful in studies of cancer. 

[DeSalle reappears on screen, speaking to the camera.]

DESALLE: Because it forms tumors. And its tumors are not unlike the tumors that we as humans form.

[Shierwater reappears on screen, speaking to the camera.]

SCHIERWATER: Cancer happens when a cell loses polarity or orientation. This is how a cell grows. 

[Shierwater holds his hand and forearm vertically.]

SHIERWATER: There's a top. There's a bottom. 

[With his other hand, he indicates the top of his fingers and the base of the hand.]

[The frame is split vertically into two distinct sections: a dark teal side on the left and a light blue side on the right. On the left is a tightly packed grid of nine oval-shaped cells arranged in a 3x3 formation. Eight of these cells are greyed out and the cell in the center of the grid is bright white with a vibrant orange-red nucleus. Two orange arrows point vertically away from the center white cell, one up and one down. Text reads “Normal Growth.”] 

[On the right side of the illustration, a single, identical white oval cell with an orange-red nucleus floats alone in the center of the field. It is surrounded by question marks.]

SHIERWATER: And if one cell, only one cell loses orientation and forgets where's top, where is bottom. Well what would happen? 

[The single cell on the right is slowly surrounded by other cells, but they appear irregularly oriented and some are distorted in shape and size. Text reads “Tumor Growth.”]

SHIERWATER: This cell would grow in a different direction. And the daughter cell another, different direction. And this growth pattern is called a tumor. 

[Shierwater reappears on screen, speaking to the camera.]

SHIERWATER: There's too many potential polarity genes related to cancer in humans, but in Trichoplax it's much more simple. The sense for polarity comes from gravity. Now we have to just take away gravity to learn about polarity, right?

[Two still images appear. On the left a cube-like container has wiring and circuit board on one of its faces, and holds four syringes secured by plastic and metal housings. On the right, about 30 people pose around a rocket with the name Mapheus 12 written on it. A long distance wide shot of a rocket launching into space.] 

DESALLE:  They've been shooting this animal up into space, robbing it of gravity and observing how it develops. 

[DeSalle reappears on screen, speaking to the camera.]

DESALLE: So, it is offering a wide breadth of possible ways of looking at biology just by looking at this one, one little animal.

[Credits roll.]