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Jellyfish in the classification of organisms belong to the kingdom of Animalia. They are sea animals that look beautiful, but sometimes can cause harm through the sting which can cause itching, convulsions, and poisoning. However, most of these jellyfish have more benefits than the disadvantages. They play role as a primary consumer in maintaining the balance of the marine ecosystem, can establish a food chain and food chain pyramid. This is a way to maintain the balance of the marine ecosystem and the preservation of marine life.

In addition, some types are used as processed food ingredients and as traditional medicines in several countries such as China, Taiwan, Japan, and Thailand. This jellyfish belongs to the Scyphozoan class or better known as true jellyfish. This is to distinguish other jellyfish in other classes such as Ctenophore (comb jellyfish) and Cubozoa (box jellyfish).

Characteristics of Jellyfish

Jellyfish, or Scyphozoan based on Animalia classification, are included in Cnidarian phylum which means animals that have sting needles. The group of Cnidarian phyla is divided into several classes, namely Cubozoa, Hydrozoa, Anthozoa, Staurozoa, and Scyphozoan. The characteristics of jellyfish include:

• Jellyfish has a dominant shape in the form of medusae in their life cycle.
• The motion system in this animal is in the form of a medusae that moves using the muscles that pull its body, so that the water in the body cavity will come out and hold it, then mesoglea in the thick and elastic jellyfish used to slide in the water and return to its original shape
• The shape is like an inverted bowl, so it is often called an inverted jellyfish bowl.
• Some have tentacles and some don’t.
• The tentacles are generally covered with stinging cells (knidocytes).
• Scyphozoan jellyfish are mostly pelagic, swimming freely in the open sea.
• Small size jellyfish eat food particles trapped from water and symbiosis with some photosynthetic algae such as dinoflagellate.
• In predatory jellyfish, in searching for prey using nematocyst organelles found in their tentacles. Nematocyst itself is a characteristic of the Cnidarian phylum, in the form of a needle-shaped cell that functions to pierce and send poisons to its prey.
• Jellyfish are diploblastic animals, in other words they have two main cell layers. The two main cell layers of jellyfish are exoderm on the outside and gastroderm inside, in the middle is mesoglea which functions as a skeleton.
• This animal has no head and mouth and the anus is located in the same hole, the side near the mouth is called oral and the other side is called aboral, so that food and dirt enter and exit through the same hole.
• The digestive system with the gastrovascular tract system consisting of the mouth, manubrium, and central branching stomach forms four stomach pockets, each of which is limited to 6 septums.
• The respiratory system of these invertebrates passes through the two layers of cells by absorbing oxygen and expelling carbon dioxide to the surroundings. Some other types are symbiotic with photosynthetic algae to get oxygen.
• The animal’s nervous system is where nerve cells are spread throughout the body where it has a muscle ring that lines the body’s dome which provides the contractile needed to swim in the water.
• The breeding of these animals undergoes metagenesis, namely sexual development followed by asexual breeding in one generation and dioecious sex. Spermatozoid exits the mouth of the male medusae and enters the intestine of the female medusae to fertilize the egg. The result of fertilization is a zygote that will develop into a blastula followed by ciliated larvae called planula. The larva planula is formed by external fertilization; they settled on a polypoid substrate known as scyphistoma. The planula will grow into a polyp. Polyps reproduce asexually by forming medusae, and so on.

Classification

In general, the classification of jellyfish (Scyphozoan) is based on the class taxonomy of the order, family to genus. The following is the order of the jellyfish (Scyphozoan):

1. Coronatae

It is also known as Crown Jellyfish and has seven families in it. This type has a distinguishing feature with other jellyfish which is the presence of deep grooves along the cover/umbrella or bowl, so as to form like a crown in accordance with the popular term. This type usually lives in the deep ocean.

This type is capable of producing and producing light called bioluminescence. When these jellyfish are touched, they will produce light, and will again appear transparent when not disturbed. When this jellyfish is attacked, this type can surprise and distract its predator with the light produced. This type can also use its light to attract prey and then dazzle and catch it. The examples of the species are Nausithoe Aurea and Atolla Wyvillei.

2. Rhizostomae

It is included in the sub-division of Discomedusae. The characteristic of this type of jellyfish is not having tentacles and other structures. Instead, this type has eight branched arms. This is different from other types which only have four arms. So generally these types of jellyfish have never been reported to have stings.

It is widely used as consumption of human food both as processed food and used as traditional medicine. This type has 10 families divided into two sub-groups. The examples of this species are Phyllorhiza Punctate, Cassiopea Andromeda, Catostylus Mosaic, Spotted Jelly or Golden Medusae Mastigias Papua, Rhizostoma pulmo, Canonball Jellyfish, and Stomolophus Meleagris.

Rhizostoma Pulmo species are commonly found in English waters, with diameters reaching 40 to 90 cm, and are generally used as processed food. Golden Medusae M. Papua is found its habitat in the Indo-Pacific. It generally has one single mouth and several small mouths on the surface of its arms, eating zooplankton. Cassiopea Andromeda species generally live in tidal sand or mud, shallow lagoons, around types of coral reefs, and around mangrove plantations. These species are often mistaken for marine anemones. They are carnivores, because they eat other smaller marine biota using nematocytes on their tentacles.

3. Semaeostomeae

Semaeostomeae, which literally means the mouth of a flag, is among the largest types of orders. This type of jellyfish is commonly known to the public. The characteristics of this type are they have four oral tentacles (long tentacles attached to the mouth), the gastrovascular digestive system consists of four unbranched pockets that protrude from the middle abdomen. It does not have a canal ring. This type also has eight tentacles, 4 in radicals and 4 in inter-radical; these tentacles also have stinging cells.

This group consists of five orders: Cyaneidae, Drymonematidae, Pelagiidae, Phacellophoridae, and Ulmaridae. To distinguish between Ulmaridae, Cyaneidae, and Pelagiidae, the gastrovascular cavity is divided into radial septa into rhopalar. For Pelagiidae, the tentacle pocket is simple and not branched. For Ulmaridae, the gastrovascular system is in the form of canals that do not branch.

For the Ulmaridae order, a well-known species is Aurelia Aurita or better known as moon jellyfish. These species generally live in colonies, measuring 25 – 40 cm, unable to move freely. Their movements tend to follow the flow. They are predators for small size medusae, types of plankton and molluscs. For the order of Cyaneidae, the species that is widely known is Cyanea Capillata or better known as Lion ‘s mane jellyfish, giant jellyfish, or hair jellyfish. This species is the largest type of jellyfish with an average size of umbrella diameter reaching 2 meters and generally living in cold areas. They are predators that prey on fish, and jellyfish that are smaller in size. The Pelagiidae order has a commonly known species, Chrysaora Achlyos or known as black jellyfish. This type can be found in the waters of the Pacific Ocean, Bay of Monteray, and waters of Mexico to Columbia.

Here you had already understood the types of jellyfish and their benefit for human life. Hopefully it can give you more insight about this marine animals.