Tentacles hang down from the smooth baglike body and sting their prey. Jellyfish stings can be painful to humans and sometimes very dangerous. But jellyfish don't purposely attack humans. Most stings occur when people accidentally touch a jellyfish, but if the sting is from a dangerous species, it can be deadly. Jellyfish digest their food very quickly. They wouldn't be able to float if they had to carry a large, undigested meal around.
They dine on fish , shrimp, crabs and tiny plants. Sea turtles relish the taste of jellyfish. Some jellyfish are clear, but others are in vibrant colors such as pink, yellow, blue, and purple, and often are luminescent. These arms are covered with stinging cells and wrap around and engulf food. This is a close up of one of these arms, gliding over a piece of glass.
This arm is about 10 cm long. Below is an extra close up. The opaque dots and bumps are bundles of stingers, each one on its own cell. You can actually see individual cells contracting. The long tube-like structure visible in the middle of the arm is where the two halves fold together, and where food is transported to the stomach. These videos are of a species called Pelagia noctiluca , and were taken by me with animals I have raised in the lab. Whoooaaaaa those are cool.
Do the stingers inject or secrete anything or are they just sharp or something? What do jellies eat, and how long does it take them to consume and digest their food? The stingers inject a toxin that is very painful, and can leave a dark bruise for several weeks.
This species eats primarily fish and other jellyfish, as well as small crustaceans. It only takes about a minute to wrap their arms around big prey, and a few seconds for something small like a little shrimp seen in the first video.
It takes a few hours to a day to fully digest food, though it also depends on temperature. Good questions! Some jellies, including this species, do eat fish. 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.
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. This jellyfish looks like a square with its four sides -- hence the name "box. 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.
The name of this type of jellyfish says it all. Deep-sea jellyfish live in very deep waters, as far as 23, feet below the ocean's surface. They are usually dark-colored -- brown, violet or black. 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. 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. 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. Jellyfish are prehistoric creatures that have inhabited oceans around the world for millions of years. Although their gelatinous bodies and graceful movements make them appear to be complex creatures, they are actually quite simple in both form and function.
Jellyfish are planktons that have no bones, brain, or heart. In fact, their bodies are mostly water and have just six major parts.
Jellyfish live anywhere from months and range in size from less than an inch to over 7 feet long. Although they are not aggressive creatures by nature, jellyfish are often remembered for their nasty stinging capabilities.
Jellyfish mostly use their tentacles for hunting, but will also sting in self-defense. When jellyfish sting humans, it is always done in self-defense since humans are far too large for any jellyfish to eat. But, aside from the occasional sting, there's no need to fear these water-based creatures from prehistoric times.
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