40 Fun Facts About Protists

Rats infected with the protist Toxoplasma gondii lose their instinctive fear of the scent of which predator?

Cats are the only hosts in which Toxoplasma can reproduce sexually, so a fearless rat may be the parasite's ticket home. Infected rats stop avoiding the smell of cat urine.

The "brain-eating amoeba" Naegleria fowleri infects swimmers when warm fresh water enters which part of the body?

The nose gives the amoeba a route along the smell nerves into the brain, where the infection is almost always fatal. Swallowing the same water causes no infection.

Which country lost a million lives in the 1840s when the protist Phytophthora infestans rotted its potato crop?

Ireland leaned on a single potato variety, the Lumper, so the blight destroyed the staple food of millions. The culprit looks like a fungus but belongs to a separate group, the oomycetes.

What kind of protist is Physarum polycephalum, the brainless yellow blob that solved a maze and copied Tokyo's railways?

A slime mold has no brain or nerves, yet it linked oat flakes laid out like Tokyo's towns with a network as efficient as the real railway. It is a single giant cell that can grow a foot or more across.

Which Egyptian monuments are built of limestone full of nummulites, the coin-like shells of giant fossil protists?

The Giza pyramids are built of stone that formed on an ancient seabed. The Greek geographer Strabo took the fossils for lentils left behind by the workers who built them.

Which wood-eating insects rely on gut protists such as Trichonympha to break down the cellulose they swallow?

Termites shelter Trichonympha in the hindgut, and it lives nowhere else except in wood-eating roaches. The protist gets food and a home, and the insect gets wood it can digest.

Which bitter extract of cinchona bark, the flavoring in tonic water, kills the protist that causes malaria?

Quinine was so bitter that British officials in India mixed their dose with soda and sugar, inventing tonic water. Adding gin to mask the taste gave the world the gin and tonic.

Which marine mammal protects forests of kelp, a giant protist, by eating the sea urchins that graze them bare?

The sea otter is a keystone species: where it disappears, urchins multiply and turn kelp forests into barrens. Some kelp can grow half a meter in a day.

Which rock, famous in the cliffs at Dover, is made of plates shed by tiny armored protists called coccolithophores?

Chalk is made mostly of plankton shells, and each coccolithophore is a single cell wrapped in plates only a few thousandths of a millimeter wide.

Which term describes the blue glow that dinoflagellates such as Noctiluca give off when waves disturb the sea at night?

Bioluminescence is light made by a cell's own chemistry, unlike fluorescence and phosphorescence, which need light shone on them first. Noctiluca flashes whenever it is jostled.

Alfred Nobel made dynamite safe to handle by soaking nitroglycerin into the fossil shells of which glassy protists?

Diatoms pile up on lake and sea floors as a soft powder called diatomaceous earth, or kieselguhr in German. The same powder filters swimming pools and beer.

A Paramecium swims by beating which structures, arranged in tightly spaced rows around the outside of its body?

Cilia beat like oars, with a stiff power stroke and a floppy recovery stroke, and a Paramecium spends over half its energy on swimming. To back away from an obstacle it reverses the stroke.

Which temporary bulges of the cell does an amoeba push out in the direction it wants to crawl?

Pseudopods, literally false feet, are not unique to protists: human white blood cells crawl through tissue on them too. An amoeba can push out several at once.

Which organelle does a freshwater Paramecium squeeze every few seconds to pump out water that floods in by osmosis?

The contractile vacuole works like a bilge pump, stopping a freshwater cell from swelling until it bursts. Some marine and soil protists have one as well.

Which green pond protist puzzled early taxonomists by photosynthesizing like a plant yet swimming with a whip-like tail?

Euglena feeds like a plant in sunlight but can live in the dark by absorbing nutrients, as an animal would. Its red eyespot helps it find the light.

The pond protist Paramecium earned an 18th-century nickname for its resemblance to which item of footwear?

A slipper is what French microscopist Louis Joblot called it in 1718, and the name slipper animalcule stuck for two centuries.

Unlike bacteria, every protist keeps its DNA inside which membrane-wrapped compartment, the mark of a eukaryotic cell?

The nucleus can come in multiples: a Paramecium carries a large macronucleus for daily business and at least one tiny micronucleus reserved for sex.

Which organelles, gained when an ancient cell swallowed a cyanobacterium, let algae and other protists live on sunlight?

Chloroplasts still carry their own DNA, a leftover from their free-living days. Many algae got theirs second-hand, by swallowing another alga that already had them.

Which process strikes reef corals when warm seas make them expel zooxanthellae, the protists that feed and color them?

Bleaching can end in starvation, because the lost protists supply up to 90 percent of a coral's energy. Corals can survive a short spell without them, but not a long one.

What name is given to blooms of toxic dinoflagellates such as Karenia brevis that kill fish and poison shellfish?

A red tide is misnamed twice over: the blooms vary widely in color, and they have nothing to do with the tides.

Which Dutch draper first saw swimming microbes, later nicknamed animalcules, through microscopes he made himself?

Leeuwenhoek wanted better lenses to inspect the thread in his cloth shop, then turned them on pond water and found it alive. He was also the first to describe bacteria.

Which protist genus, whose deadliest species is named falciparum, causes malaria by invading human red blood cells?

Plasmodium falciparum alone kills hundreds of thousands of people a year. Four other species of the genus also regularly infect humans.

After a mosquito bite, malaria parasites multiply silently in which organ before bursting out to attack red blood cells?

The liver hides the parasites at first, with no symptoms, and a single infected cell there can end up holding 40,000 of them. Some species lie dormant in it for more than a year.

Which blood-feeding African insect spreads Trypanosoma brucei, the protist behind the deadly disease sleeping sickness?

The tsetse fly injects the parasites as it feeds, and in time they reach the brain and flip the sleep cycle: victims doze by day and lie awake at night.

Which gut protist, the cause of "beaver fever", infects backpackers who drink untreated water from lakes and streams?

Giardia leaves the body as tough cysts that stay infectious for up to three months in cold water. Fever is rare, striking only about 15% of patients, despite the nickname.

Which sea, the only one with no land boundaries, is named for the golden-brown algae that float across its surface?

The Sargasso Sea is fenced in by four ocean currents instead of coasts. European eels cross the Atlantic to breed beneath its drifting weed.

Which dark sheets of dried red algae, farmed on nets in the sea, are wrapped around sushi rolls and rice balls?

Nori is made by shredding the algae and drying the pulp on racks, a process that resembles papermaking. A British scientist's study of Welsh seaweed once rescued Japan's nori farms.

Which name, coined for what seemed the simplest animals, covers protists that eat rather than photosynthesize?

Protozoa means first animals, and Georg Goldfuss coined it in 1818 for a class he filed inside the animal kingdom. Biologists now use the word only loosely, since protists are not animals.

Which freshwater alga forms hollow green spheres of up to 50,000 cells, each cell beating two whip-like tails?

Volvox takes its name from the Latin for "to roll". Its cells divide the labor: most only swim, while a few are set aside to reproduce.

Carrying one copy of the gene for which blood disorder protects against malaria, keeping the gene common in Africa?

Sickle cell disease strikes only people who inherit two copies of the gene. Those with one copy usually stay well and resist the parasite, so the gene persists wherever it is a threat.

By which process does an amoeba flow around a bacterium, seal it inside a bubble of membrane and digest it?

Phagocytosis was first clearly described in 1849 by the Swiss scientist Albert von Kölliker, who watched a protist swallow a smaller microbe. Human white blood cells eat germs the same way.

Which process sees two Paramecium cells pair up and swap genetic material without producing any offspring?

Conjugation is sex without reproduction: two cells go in and the same two come out, each with reshuffled genes. To multiply, a Paramecium simply splits in half.

Whose 1967 paper, rejected by about fifteen journals, argued that mitochondria began as free-living bacteria?

Lynn Margulis saw her idea largely ignored for another decade, until genetic evidence confirmed it. It is now the textbook account of how complex cells arose.

Which Latin American illness is spread by blood-sucking kissing bugs carrying the protist Trypanosoma cruzi?

Chagas disease is named for Carlos Chagas, the Brazilian doctor who first described it in 1909. It can stay silent for decades before damaging the heart.

Which German biologist proposed the kingdom Protista in 1866 and also coined the words ecology and phylum?

Ernst Haeckel was also a gifted artist: his book Art Forms in Nature, filled with drawings of sea creatures, went on to influence Art Nouveau design.

In which US city did the protist Cryptosporidium slip through a water plant in 1993 and sicken about 400,000 people?

Milwaukee suffered the largest waterborne disease outbreak in documented US history, because the parasite shrugs off the chlorine that kills most germs in tap water.

Which collared protists, lookalikes of the feeding cells in sponges, are the closest living relatives of animals?

Choanoflagellates take their name from the Greek for funnel, after the collar that traps bacteria for food. Biologists study them for clues to the single-celled ancestor of all animals.

In Robert Whittaker's five-kingdom system of 1969, which kingdom held the bacteria, alongside one for the protists?

Monera lumped all the simplest single cells together. From 1977 Carl Woese's gene studies showed they were two very different groups, now separate domains, and the kingdom dropped out of use.

Which British doctor won the 1902 Nobel Prize for proving that mosquitoes carry the malaria parasite?

Ronald Ross found the parasite in the gut of a mosquito in 1897, after years of dissecting insects in India. He also wrote poems and novels and composed songs.

Giant kelp has no roots, so which claw-like structure anchors it to rocks on the seabed?

The holdfast only grips: unlike a root, it absorbs nothing. In a healthy kelp forest its tangle of claws shelters a crowd of small invertebrates.