40 Fun Facts About Moon Jellyfish

Which space shuttle carried nearly 2,500 young moon jellyfish into orbit in 1991 to study weightlessness?

Columbia carried the jellies as the lone jellyfish experiment on a nine-day life-sciences mission, flying alongside studies of humans and rodents.

Which country's Oskarshamn nuclear plant shut a reactor in 2013 after moon jellyfish clogged its cooling pipes?

Sweden's plant, home to one of the world's largest reactors, had tons of the jellies cleared from its pipes before it could restart.

What are the four horseshoe shapes visible through the top of a moon jellyfish's see-through bell?

Reproductive organs, known as gonads, form the four horseshoes, and they are the mark by which a moon jelly is most readily recognized.

Roughly how much of a moon jellyfish's soft, translucent body is made up of nothing but water?

About 95% is water, leaving only a sliver of solid matter, which is why a jelly lifted out of the sea slumps into a shapeless blob.

Which of these body parts does a moon jellyfish get through life without?

Brain, heart and eyes are all missing, yet a simple net of nerves lets a moon jelly smell, taste and tell light from dark.

Which collective noun, heard alongside the term bloom, names a group of moon jellyfish swimming together?

A smack is the traditional word for the gathering, and a single one can hold hundreds or even millions of moon jellies near the surface.

Moon jellyfish share the famous snorkeling spot Jellyfish Lake with golden jellies in which Pacific nation?

Palau's lake sits on the island of Eil Malk, where the golden jellies cross the water every day while the moon jellies keep no such schedule.

Which sea turtle, the largest alive, lives almost entirely on jellies such as moon jellyfish?

Leatherback turtles follow jellies up and down the water column all day, and their appetite helps keep jelly numbers in check.

Which floating litter do sea turtles often swallow after mistaking it for a moon jellyfish or another jelly?

Plastic bags adrift in the sea look just like jellies to a hungry turtle, and a swallowed bag can block the animal's gut.

Studies of the moon jellyfish showed that jellyfish are which kind of swimmer, compared with all other animals?

The most energy-efficient swimmers known, they let the springy bell bounce back by itself, traveling 30 percent farther on each stroke.

A 2015 study found moon jellyfish share which rare ability with the tiny jellyfish Turritopsis dohrnii?

Aging in reverse, the trick that earned Turritopsis the nickname immortal jellyfish, lets a moon jelly turn back from an adult into a young polyp.

What can moon jellyfish do to survive when prey runs short, then undo once meals return?

Shrink their bodies is the trick: a hungry moon jelly can dwindle to one-tenth of its size, then grow back when food becomes available again.

What can tint a normally colorless moon jellyfish pink, lavender or orange for a while?

What it has eaten shows through the clear body: certain crustaceans turn a moon jelly pink or lavender, while brine shrimp turn it orange.

Jellies such as moon jellyfish are kept in round 'kreisel' tanks, named after the German word for which toy?

Spinning top is what kreisel means, and the tank's slow circular flow keeps delicate jellies from being hurt by pumps or by the tank itself.

Which naturalist gave the moon jellyfish its first scientific name in 1758?

Carl Linnaeus, the father of modern taxonomy, listed the species in the tenth edition of his Systema Naturae, the starting point for naming animals.

Which kind of evidence revealed that the worldwide moon jellyfish is really more than two dozen look-alike species?

Genetic samples split one supposedly worldwide species into at least 28, most of them very hard to tell apart by looks alone.

The seafloor 'polyp' stage of a moon jellyfish takes its name from a French word for which sea animal?

Octopus is poulpe in French, and the naturalist Réaumur picked the name because a polyp's ring of writhing tentacles looked like one.

The swimming adult stage of a moon jellyfish is named after which figure of Greek myth?

Medusa gave her name to the bell-shaped adult form and to Medusozoa, the wider group of animals that pass through such a stage.

Tiny mineral grains called statoliths, set around a moon jellyfish's bell, help the animal sense what?

Gravity pulls on the grains so the eyeless jelly can orient itself in the water, while light-sensing spots called ocelli tell bright from dim.

With no gills or lungs, how does a moon jellyfish breathe as it drifts along in the sea?

Through its skin: the thin membrane covering a moon jelly's body lets the gas it needs seep straight in from the surrounding seawater.

Moon jellyfish trap tiny prey on their bells with which sticky substance before sweeping it toward the mouth?

Mucus coats the bell and snags passing prey, then beating hairs called cilia carry the catch to the rim to be passed on to the mouth.

What is the main food of moon jellyfish as they pulse and drift through coastal waters?

Zooplankton, tiny drifting animals such as copepods, is the staple, though moon jellies also catch fish eggs, small mollusks and even other little jellies.

Where on her body does a female moon jellyfish carry her developing young before releasing them as larvae?

On her oral arms, the frilly flaps around the mouth, small pits act as a temporary brood chamber for the growing larvae.

Moon jellyfish belong to the phylum Cnidaria, which makes which animals their close relatives?

Corals and sea anemones carry the same kind of stinging cells as a moon jelly, the feature shared by all 11,000 or so cnidarian species.

Cnidaria, the phylum of the moon jellyfish, takes its name from the ancient Greek word for which plant?

Nettle is knide in ancient Greek, a nod to the coiled stinging threads that every cnidarian carries in its cells.

Which disc-shaped giant, one of the world's heaviest bony fishes, is a known predator of moon jellyfish?

Ocean sunfish, or Mola mola, were once thought to live mainly on such prey, but jellies and salps turn out to be only about 15% of their diet.

Caltech biologists found a young moon jellyfish that loses limbs rearranges the rest to restore which trait?

Its symmetry returns within about four days as the surviving limbs space themselves evenly, a kind of self-repair the team named symmetrization.

The bell of a full-grown moon jellyfish is often compared in size to which household object?

A dinner plate is about the size of a typical adult bell, around a foot wide, yet every moon jelly starts out as a larva less than a millimeter long.

What do keepers at the National Aquarium adjust in the tank to control when moon jellyfish breed?

Temperature is the switch: in the wild, the seasonal warming and cooling of the sea tells seafloor polyps when to bud off new young jellies.

What do biologists call the tiny free-swimming young that bud off a moon jellyfish polyp on the seafloor?

An ephyra is only about 4 millimeters across when it swims free, and a single polyp can release tens of them.

What is the name for the process in which a moon jellyfish polyp divides into a stack of discs?

Strobilation turns one polyp into a pile of discs that break away from the top one by one, and a larger polyp simply produces more of them.

What are the microscopic stinging capsules that a moon jellyfish fires to catch prey and deter predators called?

Nematocysts shoot out a coiled thread within a few millionths of a second, among the fastest movements measured in any animal.

Which giant jellyfish, whose tentacles can trail about 120 feet, preys on the much smaller moon jellyfish?

Lion's mane jellies are among the largest jellyfish known: the record specimen, found off Massachusetts in the 1800s, had a bell roughly 7 feet across.

How do most people react to being stung by the short, fine tentacles of a moon jellyfish?

Little or no reaction is the norm, because moon jellies lack the long, potent stinging tentacles that make some other jellyfish dangerous.

Besides power stations, which industry suffers when dense swarms of moon jellyfish clog and damage its gear?

Commercial fishing crews can find their trawl nets so clogged and damaged by moon jellies that they are forced to move elsewhere.

What is the name of the springy, jelly-like layer between a moon jellyfish's outer and inner cell layers?

Mesoglea acts as the animal's skeleton, holding the bell in shape with collagen and other fibers but no bone at all.

In which northern European sea was the original specimen that defines the moon jellyfish Aurelia aurita collected?

Baltic Sea waters supplied the specimen in 1758, and Aurelia aurita in the strict sense is now thought native only to the northeastern Atlantic.

Lab tests suggest moon jellyfish may recognize which tiny particles from cosmetics as something other than food?

Microbeads from cosmetics and personal care products were mostly left alone, and the few a jelly swallowed were passed within hours with no detectable harm.

Moon jellyfish belong to the class Scyphozoa, a group better known by which common name?

True jellies number only about 200 recognized species, and their class takes its name from a Greek word for a drinking cup.

Besides common jellyfish, the moon jellyfish is also known by a name borrowed from which piece of tableware?

Saucer jelly is one of several English names for the species, alongside moon jelly, common jellyfish and northern moon jelly.