The weak customer chooses the understandable rack.

The weak customer chooses the understandable rack.

The Jellyfish Sting's the Thing

Jellyfish are carnivores -- they eat other animals. Smaller jellyfish eat algae and other tiny plankton called zooplankton. Larger jellyfish eat crustaceans and other bigger aquatic animals. They don't seek out people to attack -- their nervous system is too simple to do that. Their sting is both a defense mechanism and a way to capture their prey.

Each jellyfish tentacle is covered with thousands of cells called cnidoblasts, which house nematocysts containing stinging threads. When a jellyfish encounters another object, pressure inside the nematocyst causes the threads to uncoil. The stinging cells spring out at the unwitting victim like tiny darts, firing venom into it. The venom is a neurotoxin designed to paralyze jellyfish prey. Although a jellyfish can kill a small aquatic animal, its sting is not usually fatal to humans. It tends to cause pain, skin rashes, fever and muscle cramps. The degree of pain and reaction to a jellyfish sting can depend on the species -- larger jellyfish have larger cnidoblasts that can penetrate deeper into the skin, and some jellyfish have stronger venom than others.

Image courtesy Captain Albert E. Theberge/NOAA A jellyfish washed up on a beach.

When you're at the beach, watch out for jellyfish both on the water and on the sand. Even a tentacle that has been separated from its jellyfish can sting. If you do get stung, first remove any tentacles clinging to the skin. Don't wash the area with fresh water -- it could release more venom into your body. Instead, clean it with rubbing alcohol, ammonia, vinegar or urine (yes, you read right). You can also apply meat tenderizer or a mixture of baking soda and water. Any signs of an allergic reaction (shortness of breath, hives, wheezing) warrant immediate medical attention.

Public domain Jellyfish salad, an appetizer common in Chinese and other Asian cuisines

Jellyfish have excellent protection against predators: their stinging tentacles are a strong deterrent, and their transparent bodies help them hide. A few animals, such as loggerhead turtles, sunfish and spadefish, eat jellyfish. Some young fish actually live on or even in jellyfish. They hide out in the tentacles to avoid being eaten by predators until they mature. And some people -- especially in China and Japan -- also eat jellyfish, considering them a delicacy.
Aside from their occasional stings, jellyfish are not generally a nuisance. But in recent years, certain parts of the world -- namely Japan, Australia, and Europe -- have seen a problematic increase in jellyfish populations. Scientists believe the increase in jellyfish numbers may have to do with additional nutrients in the water, climate change or fishing along the coastlines. Dramatic population increases are called blooms. Some researchers are concerned that the increased numbers of jellyfish could compete for food resources with fish and other marine animals, and eventually bump out native local species. In large numbers, jellyfish also wreak havoc with local fishing industries by tearing holes in fishing nets and disrupting other fish populations.

Image courtesy Kevin Connors /MorgueFile A smack, or small group, of jellyfish

Jellyfish do best in their natural environment, but many aquariums have jellyfish tanks. People who capture and raise them in captivity must be very careful not to damage their fragile bodies. It's easier to collect jellyfish in the polyp stage, when they are less vulnerable. Ideally, they should be in a tank free from any sharp corners or obstacles on which they could hurt themselves. In addition, the water needs to have some flow to it because jellyfish primarily move with currents.
Here are just a few of the many different types of jellyfish:
Box jellyfish
This jellyfish looks like a square with its four sides -- hence the name "box." This subclass of 16 jellyfish species includes the sea wasp. Box jellyfish tend to gravitate toward the mouths of rivers and creeks, and their sting is very painful. People who have unwittingly been stung can experience intense muscle cramps and difficulty breathing.

Image courtesy E.Widder/NOAA Ocean Explorer Atolla wyvillei, a deep-sea jellyfish

Deep-sea jellyfish
The name of this type of jellyfish says it all. Deep-sea jellyfish live in very deep waters, as far as 23,000 feet below the ocean's surface. They are usually dark-colored -- brown, violet or black.
Irukandji jellyfish
Irukandji are a type of box jellyfish found in Australia. Although they're small (about the size of a human thumbnail), their venom is extremely toxic. This type of jellyfish has cnidoblasts on its body as well as its tentacles. The Irukandji's sting is so painful and causes such severe symptoms that scientists have given them a name: Irjukadji syndrome. Symptoms include high blood pressure, vomiting, headaches, extreme cramping and pain, and a burning sensation. Irukadji syndrome can last up to two weeks, and there's no antidote. Doctors have found that magnesium infusions can bring some relief, but the syndrome can be fatal.

A moon jellyfish

Moon jellyfish
This is the type of jellyfish most commonly seen on the shores of North America and Europe. This pink or blue jellyfish usually lives in waters about 20 feet deep. Its sting is mild, leaving a red, itchy rash.


Portuguese Man-o'-war

Image courtesy NOAA

A Portuguese man-o'-war isn't a jellyfish, although it resembles one. They're actually siphonophores -- floating colonies that include four individual animals, each with its own role (for example, stinging, feeding, movement and reproduction).
Named for the 18th century ship that it resembles, the Portuguese man-o'-war is a member of the same phylum, Cnidaria, as the jellyfish. Its sting can be very painful and can lead to symptoms such as chills, fever, nausea, vomiting and shock. In some cases, the stings are fatal.

How Jellyfish Work

Jellyfish are probably some of the most unusual and mysterious creatures that you'll ever encounter. With their gelatinous bodies and dangling tentacles, they look more like something from a horror movie than a real animal. But if you can get past the weirdness -- and the fact that getting too close to one results in a nasty sting you'll discover that jellyfish are pretty fascinating. They've been around for more than 650 million years, and there are thousands of different species, with more species discovered all of the time.
In this article, we'll learn all about these mysterious animals and find out what to do if you do happen to get in the way of a stinging jellyfish tentacle.

Marine Life Image Gallery

Jellyfish live mainly in the ocean, but they aren't actually fish -- they're plankton. These plants and animals either float in the water or possess such limited swimming powers that currents control their horizontal movements. Some plankton are microscopic, single-celled organisms, while others are several feet long. Jellyfish can range in size from less than an inch to nearly 7 feet long, with tentacles up to 100 feet long.

More Marine Life.

Jellyfish are also members of the phylum Cnidaria, (from the Greek word for "stinging nettle") and the class Scyphozoa (from the Greek word for "cup," referring to the jellyfish's body shape). All cnidarians have a mouth in the center of their bodies, surrounded by tentacles. The jellyfish's cnidarian relatives include corals, sea anemones and the Portuguese man-o'-war.
Jellyfish are about 98 percent water. If a jellyfish washes up on the beach, it will mostly disappear as the water evaporates. Most are transparent and bell-shaped. Their bodies have radial symmetry, which means that the body parts extend from a central point like the spokes on a wheel. If you cut a jellyfish in half at any point, you'll always get equal halves. Jellyfish have very simple bodies -- they don't have bones, a brain or a heart. To see light, detect smells and orient themselves, they have rudimentary sensory nerves at the base of their tentacles.
A jellyfish's body generally comprises six basic parts:

• The epidermis, which protects the inner organs
• The gastrodermis, which is the inner layer
• The mesoglea, or middle jelly, between the epidermis and gastrodermis
• The gastrovascular cavity, which functions as a gullet, stomach, and intestine all in one
• An orifice that functions as both the mouth and anus
• Tentacles that line the edge of the body

An adult jellyfish is a medusa (plural: medusae), named after Medusa, the mythological creature with snakes for hair who could turn humans to stone with a glance. After the male releases its sperm through its orifice into the water, the sperm swim into the female's orifice and fertilize the eggs.

Several dozen jellyfish larvae can hatch at once. They eventually float out on the currents and look for a solid surface on which to attach, such as a rock. When they attach they become polyps -- hollow cylinders with a mouth and tentacles at the top. The polyps later bud into young jellyfish called ephyrae. After a few weeks, the jellyfish float away and grow into mature medusae. A medusa can live for about three to six months.

Wierd Fishes Part II

This two-spot Goby makes up just one of the more than 2,000 Gobiidae family.

 

Jawfish orally brood their eggs to protect from their offspring from predators.

Scorpion fish, like this leaf scorpion fish, are named for the venomous spines on their fins. In most species, the skin is brightly colored to blend in with the ocean bottom, where they dwell.

A parrotfish is familiar to many divers who can immediately identify it by the characteristic chomping noise it makes as it eats away at the coral.

The stonefish is a drab brown color and has rough, warty skin to help it blend in with the mud flats and coral reefs where it is found. The back is covered by a series of venomous spines, which can cause paralysis.

Like sharks, skates have skeletons of cartilage rather than bone. This big skate is found off the Pacific coast of North America and can reach a length of about 8 feet.

Lionfish or turkeyfish are a venomous species known their long, striped spines.

This warty frogfish stalks its prey - small sharks, squid and turtles - by crawling on its arm-like fins. It also occasionally catches a diving bird that comes too close underwater.

The Atlantic tarpon is a powerful fighter, and often makes tremendous leaps to free itself when hooked. Atlantic tarpons grow up to 8 feet in length and weigh up to 300 pounds.

If the male of a school of the anthias fish disappears, the largest female will undergo hormonal changes in order to become the ruling male.

Groupers are distinguished by their numerous dorsal spines. Most groupers are two to three feet long.

Ths Sloane's viperfish (Chauliodus sloani) is a deep sea fish that has photophores, or light organs, in its mouth and all along its body

Toadfish, like this Three-spined toadfish, have large, broad heads, and bodies that taper to a long, slender tail. Also, some species have spines that release a mild poison.
 

Snappers are usually two to three feet in length and are often brightly colored. They have deep bodies, flattened heads and large mouths with many teeth. They are predatory, feeding on other fish, crabs, squid and shrimp. Swim on over the final fish.

 

 

Butterflyfish and triggerfish are just two of the brightly-colored and incredible saltwater fish that exist.

Wierd Fishes Part I

A pair of mandarinfish swim close together prior to spawning. Mandarinfish are reef-dwellers native to the Pacific Ocean. Fish can be masters of animal camouflage.

 

This harlequin ghost pipefish has evolved to look like the coral that it lives around.

These white-eyed moray eels can grow to 4 or 5 feet long. These eels have sharp teeth in their powerful jaws. There are about 700 kinds of eels. 

A barracuda is scary because it has large jaws and very sharp teeth. It eats lots of other fish in the sea. If a barracuda feels threatened, it will even attack a person.

Batfish use their strong pectoral fins, shaped like the hind legs of a frog, to "walk" across the sea floor in search of prey.

There are over 331 known species of cardinalfish, including this Banggai cardinalfish.

There are around 360 species of shark, including this great white. Between 75 and 100 shark attacks are reported each year, but less than 20 result in human death

Clownfish, damselfish, or the "Nemo" fish, live among sea anemones, which the fish use as a place to hide from predators.

Deep-sea anglerfish, which are usually three to four inches in length, sometimes eat fish twice their own size. Only the female of the deep-sea anglerfish has the characteristic "fishing pole." Despite its name, this next fish has no relation to cattle.

 

Trunkfish, also known as boxfish or cowfish, are so named because the head and most of the body of the adult are enclosed in a boxlike structure of bone. 

 

Flouders, like this leopard flounder, live at the bottom of the sea. Lying flat on its side, a flounder can change its color and pattern to match the sea floor.  

 

The leafy sea dragons name comes from its leaf-like body, which can resemble seaweed. Sea dragons are closely related to sea horses.  

The pacific hagfish is jawless, but has plates on its mouth and tongue that rasp into the body of its prey. When threatened, it secretes defensive slime.

 

 

Stingrays, like this blue-spotted species, are considered by most experts to be docile creatures, only attacking in self-defense. A stingray's venom is not necessarily fatal, but it hurts a lot.

When a globefish, or pufferfish, is disturbed, it engulfs air or water into a special, inflatable part of the stomach. The balloon shape of a swollen fish apparently discourages attackers

 

 

 

 

Sea Creatures Part III

Soft corals, like this orange clump coral (Tubastrea aurea), have internal fleshy skeletons.

When held to the ear, a conch shell acts as an amplifier for some barely inaudible noises. 

This giant Pacific octopus (Octopus dofleini) has one or two rows of sensitive suckers on each arm, with which the octopus distinguishes different textures and tastes.


Do you know which is the deadliest of all octopuses? 

When the tiny blue-ringed octopus is threatened, its faint blue rings become bright and vivid. This animal has some of the deadliest venom on Earth. 


You may eat them, but do you know what a scallop looks like?
 

A scallop has one large, round muscle that opens and closes its shell. This muscle is the part that's eaten.

A California spiny lobster can live for more than 50 years. 

 

 

Do you know which animal is sometimes referred to as "sea pork"?

 

Sea squirts, like this goldmouth sea squirt, feed on plankton, which they filter out of the water with their pharynges. 

 

 

Many sea snails, like this flamingo tongue snail (Cyphoma gibbosum), lay their eggs on the floors of the tropical oceans where they live. 

 

 

Most sea stars have five arms each. But some have as many as 40 arms. The number of arms sea stars have often is a multiple of five

Sea Creatures Part II

An Antarctic giant isopod (Glyptonotus antarcticus) and a few sea stars (Odontaster validus) are frozen in newly formed anchor ice.

This bigfin reef squid (Sepioteuthis lessoniana) is torpedo-shaped and more closely resembles cuttlefish than squid

Long-armed starfish (Luidia sarsi) has recently metamorphosed after casting off its larval body.

Octopuses have poisonous saliva and the bite of some species can be fatal to humans.

Fire coral (Millepora alcicornis), a hydrocoral, stings fiercely upon contact

A candy-cane sea star (Fromis monilis) is within arm's reach of a feather star (Comanthina nobilis).

Here's a close-up of a fierce sand crab. Crabs have 10 legs, and in some species, the front two are modified to form large, pincherlike claws. Which animal do they call the "hedgehog of the sea"?

The iridescent red-and-blue spines of the globe urchin give it a formal look, which lends to its other nickname, the "tuxedo urchin."

This sea cucumber has its feeding tentacles extended. After sea cucumbers catch food this way, they stuff their tentacles into their mouths

A strawberry anemone (Tealia lofotensis) captures drift kelp with its tentacles. The animal feeds on kelp and encrusting animals.