40 Fun Facts About Clownfish

What does the breeding male in a clownfish group do when the group's top-ranking fish disappears?

He changes sex: the male becomes the group's new breeding female, and the next fish in line takes over as her mate. The switch can take months to complete.

What covering a clownfish's body is thought to stop a sea anemone from stinging it?

A layer of mucus does the trick, seeming to copy the anemone's own slime so its stinging cells never fire. A newcomer still spends minutes or even days getting used to its host.

Which fish does most of the clownfish egg care, guarding and fanning the clutch until it hatches?

The father does the babysitting, cleaning the clutch and fanning it with his fins for the six or seven days it takes to hatch.

Given small and large bits of food in experiments, what does a clownfish do with the large ones?

It feeds them to its anemone and keeps the small pieces for itself. The host gets more than meals from its lodger, which also picks off its parasites.

How do orange clownfish cope when a marine heatwave makes the water around them too warm?

They shrink their bodies to handle the heat stress. Fish that shrink along with their breeding partner have a better chance of surviving the heatwave.

Sea anemones, the stinging hosts of clownfish, are close relatives of which other sea animals?

Jellyfish, corals and sea anemones all belong to one group of stinging animals, the cnidarians. Unlike its drifting cousins, a typical anemone lives attached to a hard surface.

Sea anemones, the colourful homes of clownfish, are named after which kind of living thing on land?

A flower called the anemone lent its name, because the sea creature looks just as colourful. The sea version is no plant, though: it is a predator that catches prey.

What is the name of Nemo's overprotective clownfish dad in the film Finding Nemo?

Marlin travels a very long way to find his son, and learns on the journey to take risks and let Nemo look after himself.

Sea anemones grow and heal faster with clownfish living in them, thanks to nutrients from what?

Fish waste works as fertiliser: its ammonium helps the anemone grow and repair itself. The droppings also draw in the tiny light-using microbes that anemones depend on.

Clownfish see in colour and can also detect which kind of light that human eyes cannot?

Ultraviolet light is visible to a clownfish, helped by small gaps between the iris and the lens that let extra light into each eye.

In Finding Nemo, Nemo's clownfish family lives on the edge of which natural wonder off Australia?

Great Barrier Reef scenery had to look right, so the film's artists took scuba diving lessons to study living coral up close.

In Finding Nemo, the captured young clownfish Nemo ends up in a fish tank in which Australian city?

Sydney is where Nemo is taken, and his rescuers arrive in style: a whale blows them out through its blowhole into the harbour.

Which animation studio made Finding Nemo, the hit film that turned a clownfish into a movie star?

Pixar made the film for Walt Disney Pictures, and it won the Academy Award for Best Animated Feature, the studio's first win in that category.

Early in Finding Nemo, which predator attacks the clownfish home and leaves just one egg?

A barracuda strikes in the opening minutes, and the single egg left behind hatches into Nemo. The loss is why his dad becomes so anxious about letting him out of sight.

Finding Nemo's director traced his clownfish story to a fish tank he loved as a child where?

At the dentist, the young Andrew Stanton loved watching the fish tank, and he imagined its fish had come from the sea and wanted to go home.

Clownfish live across the Indian and western Pacific oceans, but which warm sea has no wild ones?

Caribbean Sea reefs have no wild clownfish, and neither does the rest of the Atlantic or the Mediterranean. The group is thought to have started out around the Malay Archipelago.

Following about a week of care, at what time of day do baby clownfish usually hatch?

After dark is hatching time: the babies break out of their egg capsules at night. The eggs start out bright orange and darken as hatching day gets close.

Clownfish breed all year in tropical seas, with spawning mostly happening during which lunar phase?

Full moon is when most spawning happens. Beforehand the male courts his partner by chasing and nibbling her, then holding still with his fins raised.

Where does a clownfish pair lay its eggs after spending time cleaning the chosen spot?

On a nearby rock, close to the anemone that keeps the family safe. Each cone-shaped egg is stuck down by a bundle of short fibres.

Feeding takes up most of a clownfish's day, and which food makes up most of the menu?

Plankton such as algae and tiny animals called copepods makes up most of the diet. Clownfish also nibble the leftovers their anemone discards.

Clownfish belong to which larger family of mostly small, colourful tropical sea fish?

Damselfish are the wider family, and the clownfish branch split from the rest of it tens of millions of years ago.

Which word names the biggest clownfish species, whose females grow to about 17 centimetres long?

Maroon clownfish females dwarf their mates, which usually reach only 6 or 7 centimetres. The species is also rated the most territorial of all the anemonefish.

Which clownfish is the least fussy about its home, living in all ten host sea anemone species?

Clark's anemonefish will settle in any of the ten, and it is also the most widely spread clownfish of all. Several other species accept only a single kind of host.

Why do low-ranking clownfish hold back their own growth and stay smaller than the fish above them?

To avoid being evicted: the fish in charge drive off any that grow close to them in size. Nearby anemones are already taken, so a small fish has nowhere else to go.

Clownfish keep order with clicks, grunts and pops; which body parts appear to produce the sounds?

Jaws and teeth appear to make the noise, and the swim bladder amplifies it. A bossy fish gives long pulses while it chases; the loser answers with quicker ones.

Where do newly hatched clownfish spend their first days of life, before settling down as juveniles?

Out in the open ocean, the larvae drift for up to 12 days before sinking to the bottom to look for a host. One kind, the Oman anemonefish, has been carried more than 400 km.

What do newly hatched clownfish larvae look like, before the famous orange and white appears?

Almost transparent at first, a larva shows little more than its eyes, its yolk sac and a few specks of pigment. Colour and fins develop as it grows.

Clownfish guard their sea anemone hosts by chasing off which anemone-eating reef fish?

Butterflyfish such as the raccoon butterflyfish like to nibble anemones, so the resident clownfish drive them away. An anemone can live without a guard, though, and many do.

Warming seas cause which change in sea anemones, seen as the greatest threat to wild clownfish?

Bleaching, the same trouble that hits corals, is known in nearly every anemone species that clownfish live in. Where hosts bleach, clownfish numbers fall.

Which clownfish, also called the common clownfish, ranks among the most traded marine aquarium fish?

Ocellaris clownfish made up almost half of all the clownfish imported into the United States in one 2011 count. It is the orange, three-barred fish most people picture.

Captive-bred fish with unusual new colour patterns are sold as which kind of clownfish?

Designer clownfish include a 'misbar' type whose white bars are left unfinished and a golden type that lacks the cells for black and white.

The clownfish genus name Amphiprion refers to jagged gill-cover edges that resemble which tool?

A saw is the idea: the name joins Greek words for 'on both sides' and 'saw'. The notched edges run along the gill covers and under the eyes.

In a clownfish group sharing one sea anemone, which members are the ones that breed?

Only the two largest breed, while the rest are smaller non-breeders waiting in line. The fish sharing an anemone are not even related to one another.

Where does a wild clownfish rest at night, when feeding around the coral reef is over?

Deep among the tentacles of its anemone is the safest bed on the reef. Even by day a clownfish never strays far, and the smallest fish rarely leave the anemone's central disc.

A clownfish's rapid fin movements help its host sea anemone by bringing it more of what?

Oxygen reaches the anemone faster as its lodger wriggles and fans, stirring the water around it. In return the fish gets a home that few predators dare approach.

Which term describes a partnership like that of clownfish and sea anemones, where both sides benefit?

Mutualism means both partners gain: the fish gets a safe home, and the anemone gets a bodyguard and a cleaner that removes its parasites.

What does a clownfish parent do with any eggs in the nest that go bad?

Eats them: bad eggs are swallowed before they can rot and spoil the healthy ones beside them. A single clutch can hold hundreds of eggs.

On a clownfish species with just one white vertical bar, where on the body does the bar sit?

On the head: bars form from the front backwards, so a second bar sits on the trunk and a third near the tail. One species, the red saddleback anemonefish, has none at all.

Which sense do young clownfish mainly use to find the right kind of sea anemone to settle in?

Smell guides them: host anemones release chemical cues into the water, and the young fish follow the scent. More acidic seawater appears to dull this sense.

In Finding Nemo, the forgetful Dory who helps the clownfish hero is which kind of fish?

Blue tang is right, or regal blue tang in full: a royal-blue fish with a yellow tail and a black pattern shaped like a painter's palette.