The Egyptian pyramids are a monument to human engineering, preserving both culture and mummies
across millennia. But for the purposes of our microcosmic journey, what’s most remarkable about
them are the bits of fossils that made up their limestone. As far back as the 5th century BCE,
the Greek historian Herodotus noticed these shells embedded in the pyramids.
What he did not know is that these shells were the remnants of creatures that are just
as intriguing as the pyramid’s own inhabitants. In the early 19th century, far removed from those
pyramids, a young boy named Alcide d’Orbigny would become fascinated with the tiny shells
he found on the beach. And when he grew up and expanded his hobby into a more professional study,
he named them and the organisms they came from. He called them foraminifera.
If you judge them just from appearances, it might be a surprise to learn that foraminifera
is an amoeboid protist, meaning that inside that hard shell--which is also
called a test--there is a squishy amoeba. While we don’t know too much about how
foraminifera evolved from other eukaryotes, we know that they’ve been around for over
500 million years. And over that time, they’ve evolved at least 10,000 species that are still
living today and another 40,000 species that we know only through their fossils.
There are two different main types of foraminifera. Most of the living species
we know are benthic foraminifera, which means they’re found throughout the ocean’s depths,
living on rocks and seaweed or just the ocean floor. They’ve even been found in abundance in
the Challenger Deep, the deepest known point in the ocean. The second group are the planktonic
foraminifera, which float on or near the surface of the ocean thanks in part to their tests.
Both types of foraminifera make and inhabit tests. And scientists can use the materials
and test morphology to distinguish between different species. Some foraminifera secrete
compounds like calcium carbonate, while others glue bits of inorganic particles
together with the organic equivalent of cement. And inside, the tests are divided into chambers,
with some species creating complex structures out of these chambers the way we might create complex
arrangements of rooms in a building. Foraminifera are architects, and as they grow, they build more
chambers to accommodate themselves. Some grow so fast they have to add a chamber every day.
The shapes of these chambers play a particularly crucial role for planktonic foraminifera,
which generally build less complex structures compared to their benthic counterparts.
The chambers they build are more globular, which provides the planktonic foraminifera
with a means to stay buoyant as they float around. But foraminifera, or “forams” as they call them in
the biz, don’t just build shells, they also build webs. Or more accurately, they become webs.The
foraminifera tests are lined with holes that act like little windows to allow the organism’s
pseudopodia, or “false feet” to peek out. And “peeking” might be an understatement.
The pseudopodia reach and reach out, forming their own webs as they do to find
food and catch it. These forms of pseudopodia are called reticulopodia, and you can see here
just how weird and extensive they are in action. They may look like a disintegrated spider’s web,
but remember that this is the organism reaching its own body out to the microcosmos,
spreading itself thin as it contorts into new shapes. Zoom in on those reticulopodium,
and you can see the cytoplasm streaming through it like a biological highway.
When forams die, the soft matter that makes up those pseudopodia will eventually decay,
but what remains are the tests. And over the hundreds of millions of years they’ve existed,
the death of foraminifera has become integrated into our planet’s geology.
Large swathes of the ocean floor are covered in the collected remains of planktonic foraminifera,
creating a dense substance called Globigerina ooze. And we owe famous sights like the
pink-tinted beaches of Bermuda and the nummulitic limestone of the Pyramids to ancient foraminifera.
And the abundance of these fossilized remains provides us with a record of our planet’s history.
While forams may be found throughout our oceans, individual species have their own environmental
needs, whether that means they prefer a particular temperature or salinity or light condition. So
assessing the fossil composition of different sediments helps scientists understand what
our world once looked like. And understanding the past shapes our present as well, with oil
companies using microfossils to understand the geology of the area they’re working in.
So where did our fossils come from? Well, they had a bit of a journey. James, our master of
microscopes, got these samples from Virginia by way of his fiancée, who collected water and sand
from the coast and packed them in a jar. If that seems like an easy enough way
to give the lovely gift of microbes to a microscopist, just remember that she had
to take the samples from Virginia to Poland. And that’s where things started to go wrong.
First the jar of sand and water leaked all over her luggage. Then after she arrived,
James’ cat tipped over the jar, as cats do like to do. But we cannot blame the cat for all the
subsequent damage either because James also tipped the jar over while trying to open a window.
On the one hand, this story seems like something of a cautionary tale on the importance of
careful jar handling. But even after having lost all that water, the jar
was still full of sand—and also what turned out to be a whole bunch of foraminifera fossils.
And maybe that’s the true lesson to take from our shelled, amoeboid friends:
that even when the world around them has tipped and turned and leaked, even then
you can find something dazzling in what remains.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
And thank you to everyone who has so far backed our Kickstarter project
of the Microcosmos microscope. We’ve blown past our goal and I’m very excited that we’ll
be sharing these with you. I’ve really been enjoying mine. I need to make my
technique better because I’ve actually hurt my neck a little bit looking into it so much.
Thank you also of course to all of our patrons on Patreon. These people whose names are on the
screen right now. These folks are the reason we are able to make Journey to the Microcosmos.
Everyone of you, thank you so much for giving us this opportunity
to make stuff for you and for everyone. If you want to see more from our Master
of Microscopes James Weiss, you can check out Jam & Germs on Instagram,
and if you want to see more from us, there’s always a subscribe button somewhere nearby.