Flatworms
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40 free Flatworms trivia questions with answers — trivia quiz, new questions added Oct 2026.
Flatworms look like the simplest animals imaginable: soft, ribbon-thin and without lungs, blood or a skeleton. Yet the phylum Platyhelminthes is packed with some of the strangest stories in biology, from planarians that rebuild themselves after being sliced into pieces to parasites that steer the behaviour of the animals they infect. This quiz turns those stories into fun facts you can test yourself on. It covers how flatworms feed, breathe, sense the world and reproduce, the tapeworms and flukes that live inside people and livestock, the dazzling polyclads of coral reefs, and the land species now turning up in gardens far from home. A few questions look at the scientists and experiments that made these worms famous in the laboratory. It is written for curious readers, biology students revising invertebrates and teachers who want a ready-made review. Every answer comes with a short explanation, so the set doubles as a study sheet.
30 of 40 questions with answers and explanations. Play the quiz
Q 01Which US president's surname is also a genus of leaf-shaped flatworms, named from Tupi words for 'leaf animal'?
Obama
Obama joins the Tupi words oba, leaf, and ma, animal, so the match with the 44th president is pure coincidence. One species, Obama nungara, has spread from South America to Europe.
Q 02Which mating duel do some large marine flatworms fight, with the loser left to carry the eggs?
Penis fencing
Penis fencing can last up to an hour, as each worm tries to stab and inseminate its rival while dodging the same fate. The winner escapes the costly work of developing eggs.
Q 03A cut planarian flatworm regrew with a head at each end after five weeks aboard which orbiting laboratory?
The ISS
The ISS carried the worm pieces for a Tufts University study, and one fragment came back double-headed. Electric fields can trigger the same oddity on Earth.
Q 04The green-banded broodsac flatworm pulses inside a snail's eye stalks, mimicking which prey to lure hungry birds?
Caterpillars
Caterpillars are what the throbbing, striped sacs resemble, and the parasite also keeps its snail in brighter, higher spots. Birds have been seen tearing out only the sac, so the snail may live on.
Q 05The parasitic flatworm Ribeiroia ondatrae is blamed for which pond animals growing extra or missing hind legs?
Frogs
Frogs pick up the larvae as tadpoles, when the parasites settle around the budding hind limbs. A deformed adult is easier for a heron or hawk to catch, which carries the worm to its final host.
Q 06Bipalium land flatworms carry tetrodotoxin, a nerve poison best known from which fish served as fugu in Japan?
Pufferfish
Pufferfish made the poison infamous, but in 2014 two of these worm species became the first land invertebrates found to carry it.
Q 07Researcher James McConnell claimed in the 1960s that planarians could gain what by eating ground-up fellow worms?
Memories
Memories seemed to pass from trained worms to the cannibals that ate them, but other laboratories could not reliably repeat the result.
Q 08Most flatworms have no anus, so undigested food leaves the body through which part?
The mouth
The mouth doubles as the exit, because most flatworms have no anus and simply regurgitate what they cannot digest. A few long species break the rule and have one or more.
Q 09The longest tapeworm known, which can stretch past 30 metres, lives in the gut of which sea animals?
Whales
Whales such as the sperm whale host Tetragonoporus calyptocephalus, whose body can run to 45,000 segments. It probably sheds billions of eggs in a lifetime.
Q 10Larvae of the tapeworm from which undercooked meat can lodge in the human brain and trigger seizures?
Pork
Pork tapeworm larvae that settle in the brain are among the commonest causes of seizures in developing countries. People catch that form by swallowing the worm's eggs, not by eating the meat.
Q 11Schistosomiasis, spread by blood flukes, ranks second only to which other parasitic disease in the tropics?
Malaria
Malaria alone does more damage in the tropics than these worms, whose larvae bore into people who wade, wash or swim in infested fresh water.
Q 12Schistosome eggs have turned up in mummies from which country, where the blood fluke was first identified?
Egypt
Egypt is where the worm was first described, in 1851, and its eggs have since been found in mummies about 3,000 years old.
Q 13Schistosomiasis is also known by which name, honouring the German doctor who found its worm during autopsies?
Bilharzia
Bilharzia honours Theodor Bilharz, who spotted the worm in 1851 while working at a Cairo hospital. He died at 37 of a fever caught on an expedition.
Q 21Flatworms have no lungs, gills or blood vessels, so oxygen reaches their cells by which simple process?
Diffusion
Diffusion only works over tiny distances, which is why a flatworm has to be flat: no cell can sit far from the surface.
Q 22Adult tapeworms have no gut at all, so what do they use to soak up digested food inside a host?
Their skin
Their skin, a living layer called the tegument, absorbs sugars and amino acids and also shields the worm from the host's digestive juices.
Q 23What do planarians mainly use their two cup-shaped eyespots to do?
Avoid light
Planarians avoid light, and their eyespots cannot form images: they only tell which direction the light is coming from. Cave-dwelling species are often eyeless.
Q 14The lancet liver fluke makes which infected insects climb grass blades each evening, to be eaten by grazing sheep?
Ants
Ants carrying the fluke clamp their jaws onto a grass tip at dusk and hang there until dawn, night after night, until a grazing animal swallows them.
Q 15The broad fish tapeworm can absorb most of the vitamin B12 in a person's food, leading to which blood condition?
Anaemia
Anaemia can follow because the worm takes around 80% of the B12 its human host eats. Averaging ten metres, it is the longest tapeworm found in people.
Q 16The New Zealand flatworm, an invasive pest in Britain and Ireland, feeds almost entirely on which soil animals?
Earthworms
Earthworms are almost its only food in Europe, which degrades the soil they keep healthy. At rest the flatworm coils up like a tiny Swiss roll.
Q 17The New Guinea flatworm was deliberately released on Pacific islands to control which crop-eating invader?
Giant African snail
Giant African snail control backfired: the flatworm also devoured rare native snails and now ranks among the world's 100 worst invasive species.
Q 18Which structures, bundled into organs called protonephridia, act as a flatworm's simple kidneys?
Flame cells
Flame cells are named for the tuft of beating flagella inside each one, which flickers like a candle. They drive waste water out through tiny pores.
Q 19The word 'fluke' for a parasitic flatworm comes from the Old English name for which flat-bodied fish?
Flounder
Flounder was 'floc' in Old English, and the leaf-shaped parasites were named for sharing its flattened, diamond-like outline.
Q 20The old flatworm class Turbellaria is named for tiny whirlpools the animals stir up using which structures?
Cilia
Cilia, the microscopic beating hairs that coat the body, churn the water into the little whirlpools behind the name. Small species also swim with them.
Q 24A planarian eats through a muscular tube that extends from the middle of its underside; what is the tube called?
Pharynx
Pharynx is the name for the tube, and some land planarians use it to pour enzymes over their prey and then suck up the liquefied remains.
Q 25Two young Diplozoon paradoxum flatworms that meet on a fish's gills are famous for doing what for life?
Fusing together
Fusing together is the only way they can mature, and a larva that never finds a partner usually dies. The joined pair can live for several years.
Q 26Which rash do lake bathers get when the larvae of bird-infecting flatworms burrow into them by mistake?
Swimmer's itch
Swimmer's itch flares because the larvae die as soon as they get in, and each raised spot marks a single parasite. They were hunting for a water bird.
Q 27People can catch the sheep liver fluke, Fasciola hepatica, by eating which raw salad plant?
Watercress
Watercress grows in the wet ground where the fluke's young stages leave their host and form cysts on plants, waiting to be eaten.
Q 28The Chinese liver fluke, caught from raw freshwater fish, is officially classed as a cause of which illness?
Bile duct cancer
Bile duct cancer is tied so firmly to the fluke that the international cancer research agency lists the worm as a group 1 carcinogen, its top category.
Q 29Hydatid disease comes from a tiny tapeworm whose eggs people usually pick up from which domestic animals?
Dogs
Dogs carry the adult worm, barely 6 mm long, after eating infected sheep offal. In people its eggs grow into fluid-filled cysts that can last for years.
Q 30Which drug, on the WHO's list of essential medicines, is the standard treatment for schistosomiasis and tapeworms?
Praziquantel
Praziquantel was developed in Germany by Bayer and Merck in the 1970s, and a single yearly dose is given to whole communities where schistosomes are common.