Jellyfish
Jellyfish are invertebrates, which, together with corals, gorgonians and anemones belong to a group called the cnidarians. This animal group has stinging cells which they use both to capture their prey and also for self-defense. These cells contain a capsule in the interior of which there is a rolled up filament and a poison. A prey animal makes contact with the surface of the jellyfish, the capsule opens and the filaments are ejected and stick into the prey, injecting their poison. Because their body is 95% water, which means they are perfectly camouflaged. The body of a jellyfish is divided into three main parts, the umbrella, the oral arms (around the mouth) and the stinging tentacles. They are animals with radial symmetry. They have an internal cavity, in which the digestion is carried out, denominated the gastro-vascular cavity and which has a single aperture which carries out the functions of both the mouth and the anus. In order to reproduce, males and females release sperm and eggs into the water. After fertilization, they develop larvae which give rise to new jellyfish or which settle on the bottom of sea as polyps. From these polyps, by means of asexual reproduction, new free-living jellyfish may develop.
Jellyfish are inhabitants of the tropical seas and of the cold waters of the Arctic. They have been there for over 650 million years. Jellyfish are pelagic animals that is to say that they live in the open seas, and although they can propel themselves with rhythmic motions of their umbrella, they move basically at the mercy of the currents of the sea.
There are two phases to jelly life: the stationary polyp stage and the mobile medusa phase. It’s the medusa phase that we’re usually referring to when we talk about jellyfish. Typically, jellies start as polyps and develop into medusas, but the Turritopsisnutricula has earned it the nickname “the immortal jellyfish” for having the ability to travel backward to the polyp stage in times of stress.
Jellyfish are carnivores and can increase in size rapidly and create a large number of individuals when food is abundant. However, if food is scarce, they can become smaller. These animals, of a gelatinous consistency, have very unsophisticated anatomy which is nevertheless very effective. They feed mainly on zooplankton, small crustaceans, although some small fish and other jellyfish also form part of their diet. It is a strange sight to see the jellyfish’ latest prey inside its body before it is digested.
If a jellyfish is cut in two, the pieces of the jellyfish can regenerate and create two new organisms. Similarly, if a jellyfish is injured, it may clone itself and potentially produce hundreds of offspring.
Jellyfish should not be touched in the sand, even though they appear to be dead, the stinging cells remain active for a period of time; even walking along the water’s edge can be dangerous as there may be remains of tentacles in the sand. It is necessary for a period of a day’s sun to de-activate the stinging cells located in the fragments.
There are more than 1500 types of jellyfish that have been identified, yet experts believe that there are many more species that are still not known. While jellyfish do not have eyes or a visible brain, these beautiful creatures have a strong nervous system that can detect light, odor and external stimuli that generates appropriate response, thus making them mysterious and intimidating in many ways. Here are some well-known types or species of Jellyfish.
Species of Jellyfish:
Moon Jellyfish (Aurelia Aurita)
This is the most common species in the world and can be identified by the four horseshoe-shaped gonads that can be seen through the top of the bell. The size ranges between 6 and 20 inches. They mainly feed on plankton and rely on currents for drifting as they have limited locomotion.
Cannonball Jelly (Stomolophus meleagris)
Cannonball Jelly’s name is derived from its resemblance to a cannonball. This type of jellyfish can be easily identified as they have white bells at the bottom that are surrounded by a ring of purple or brown pigment. Its size ranges between 8–10 inches. They mainly feed zooplankton. Another common name given to the species is Cabbage Head Jellyfish.
Lion’s Mane (Cyanea Capillata)
Lion’s mane jellyfish is the largest known species of jellyfish. They are distinguished by a saucer-like shape on the top and tentacles hanging below as thick as a lion’s mane. Found in the freezing waters of the Arctic Ocean and the Northern Pacific Ocean, they are known to survive in the coldest weather conditions. The largest recorded specimen was about 8 feet in diameter and about 150 feet long. Even though their stings are not known to be fatal, it can lead to temporary pain and redness in the area of contact.
Atlantic Sea Nettle (Chrysaora quinquecirrha)
These jellyfish are found in tropical and subtropical parts of the Atlantic and Indo-Pacific oceans. The body size varies from 6–8 inches and tentacles may grow up to 6 feet long, they are smaller than the Pacific sea nettle species. Atlantic sea nettle is distinguished by the reddish-brown stripes that run along the head. The sting is not lethal but leaves a painful rash.
Jelly Blubber (Catostylus mosaicus)
Also known as Blue Blubber jellyfish, this species of jellyfish are distinguished by their large bells and translucent oral arms which range from 4 to 8 in number. They use these arms to capture and ingest their food. Blue Blubber stuns its prey using the venomous tentacles. However, this sting is not fatal to humans. It may cause minor rash or itchiness in the area of contact.
Mauve Stinger (Pelagia Noctiluca)
This species of jellyfish has an ability to glow in the dark. In Latin, “nocti” means night and “luca” stands for light. Roughly the size of a golf ball, these are known to survive in warm and temperate waters of Mediterranean Sea, Red Sea and Atlantic Ocean. Their stings are slightly painful, but are limited to only a small period of time and do not cause much harm.
Blue Jellyfish (Cyanea lamarckii)
Also known as “Bluefire jellyfish”, these have a blue or yellow color tone and grow to approximately 10 to 20 cm in length. They are mainly found off the west coast of Scotland, the North Sea and the Irish Sea.
Irukandji Jellyfish (Carukia Barnesi)
Irukandji Jellyfish is extremely tiny and extremely venomous species of jellyfish. If left untreated, the sting can lead to cardiac arrest. The bell of this species grows only up to 5 to 10 millimeters and tentacles are a few centimeters to 1 meter in length. They are usually found in warmer waters near the coast.
Sea wasp (Chironex fleckeri)
Sea wasp is a species of Box jellyfish; it is the most lethal jellyfish in the world. Mostly found in the coastal waters of Northern Australia and New Guinea, this species has venomous tentacles up to 3 meters (9.8 ft) long. At least 63 deaths due to sea wasp encounters have been recorded in Australia. The sting results in excruciating pain and, if left untreated, the victim can die within 3 minutes.
Immortal Jellyfish (Turritopsis Nutricula)
This species has a very strange attribute of going back to its juvenile stage after attaining sexual maturity. Scientists believe that this species can turn back its life cycle indefinitely, thus making them immortal. Originally from the Caribbean, this 5 millimeter long creature has steady population across the world, attracting the curiosity of experts all over.
Upside-down jellyfish (Cassiopea andromeda)
Often mistaken for a sea anemone, Upside-down jellyfish lives in mud flats, shallow lagoons, and around mangroves. They can measure up to 300 mm wide. Cassiopea andromeda is carnivorous and eats small animals. The stinging cells, or nematocysts, cover its tentacles and are used for feeding or defending. This jellyfish is fairly venomous; contact may result in pain, rash, swelling and vomiting.
Four-Handed Box Jellyfish (Chiropsalmus quadrumanus)
Also known as the box jelly due to its cube-shaped bell or Chironex Fleckeri, it is one of the most venomous species of jellyfish in the world. The tentacles can inflict an extremely painful sting on contact. Apart from pain, the sting may also lead to cardiac dysfunction and respiratory depression, which can be fatal. They grow to about 5 inches in diameter and the tentacles can be 3 to 4 meters (9.8 to 13 ft) long.
