Scyphozoa is a class under the phylum Cnidaria. It is a marine class. Scyphozoa is also called true jellyfish or true jellies. This class may include Conulariida (a fossil group). The affinities of Conulariida are widely spread and uncertain. The name Scyphozoa is derived from skyphos. Skyphos is a Greek word that refers to a cup-shaped organism. Skyphos denote a cup of drinking. Scyphozoans are found from the earliest Cambrian to time. It is an interesting class and has a lot of species under it. Their life cycle depends on two main phases. These jellies have all the basic characteristics of a jellyfish.
Scyphozoa life cycle has two main stages. These stages are predominant medusa stage and small inconspicuous polyp stage. Only Stauromedusae species do not have two stages of life. In the medusa stage, they have an umbrella-shaped body. It has two epithelial layers that are separated by mesenchyme (a gelatinous connective tissue). Their tentacles of Coronatae and Semaeostomeae are used for feeding. The tentacles have small cells called nematocysts that help to inject a toxin in the host. The species Semaeostomeae have smallmouth arms on the underside of the bell. These are used to sting the host and feed. The polyps are called scyphistomae.
There are a total of 200 species under the class Scyphozoa. Other than 20 species, there are four orders and 66 genera and 20 families under Scyphozoa. The four main orders include the stalked jellyfish (Stauromedusae), grooved or crown fish (Coronatae), Semaeostomeae, and Rhizostomeae. All the species of Scyphozoa have a two-stage life cycle except Stauromedusae. It is only found in benthic stages (polyp form). It is considered the medusa. The others, including Coronatae, Semaeostomeae, and Rhizostomeae, have both stages in the life cycle. They are mostly found in the medusa stage. It is the largest and most conspicuous state.
All the scyphozoans feed via two methods. They either feed with their tentacles and the sting like projections under their bell. The projections have numerous cells called nematocysts. These cells are used to paralyze or kill the prey. The other stings entangle the prey. Stauromedusae holds the prey with its tentacles. It holds it by folding its arms inward around it. While feeding, the medusae do not swim at all, but instead, they remain still. The different species eat different things. Usually, they eat fishes, fish larvae, zooplankton, and gelatinous species. The food also depends on availability.
Scyphozoa Facts
Scyphozoa life cycle has two main stages. These stages are predominant medusa stage and small inconspicuous polyp stage. Only Stauromedusae species do not have two stages of life. In the medusa stage, they have an umbrella-shaped body. It has two epithelial layers that are separated by mesenchyme (a gelatinous connective tissue). Their tentacles of Coronatae and Semaeostomeae are used for feeding. The tentacles have small cells called nematocysts that help to inject a toxin in the host. The species Semaeostomeae have smallmouth arms on the underside of the bell. These are used to sting the host and feed. The polyps are called scyphistomae.
Scyphozoa Life Cycle
The life cycle of Scyphozoa depends on two main parts. These two parts are bottom-dwelling polyp and free-swimming medusa. The medusa form can be female or male, producing eggs or sperms, respectively. They fuse to form a planula. The planula travels and finds the most suitable place to attach on. Usually, it attaches itself to the surface. After attachment, it goes through metamorphosis. Due to metamorphosis, it converts to the sessile bottom-dwelling polyp. The polyp form is called scyphistoma. It remains attached to the same surface. Later on, it again converts into a medusa. Strobilation is the process by which a polyp again converts into a medusa.
Scyphozoa Species
There are a total of 200 species under the class Scyphozoa. Other than 20 species, there are four orders and 66 genera and 20 families under Scyphozoa. The four main orders include the stalked jellyfish (Stauromedusae), grooved or crown fish (Coronatae), Semaeostomeae, and Rhizostomeae. All the species of Scyphozoa have a two-stage life cycle except Stauromedusae. It is only found in benthic stages (polyp form). It is considered the medusa. The others, including Coronatae, Semaeostomeae, and Rhizostomeae, have both stages in the life cycle. They are mostly found in the medusa stage. It is the largest and most conspicuous state.
Scyphozoa Diet
All the scyphozoans feed via two methods. They either feed with their tentacles and the sting like projections under their bell. The projections have numerous cells called nematocysts. These cells are used to paralyze or kill the prey. The other stings entangle the prey. Stauromedusae holds the prey with its tentacles. It holds it by folding its arms inward around it. While feeding, the medusae do not swim at all, but instead, they remain still. The different species eat different things. Usually, they eat fishes, fish larvae, zooplankton, and gelatinous species. The food also depends on availability.
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