9 Facts On Medusozoa Characteristics, Life Cycle

Medusozoa is the subphylum of the phyla-Cnidaria. Let us discuss some of its characteristic features.

  • Medusozoa is a cnidarian having a medusa stage in their lifespan.
  • Medusozoa are aquatic organisms and exhibit radial symmetry.
  • Medusozoa are umbrella-shaped organisms with hanging tentacles.
  • Medusozoa possess stinging tentacles through which they can capture their prey.
  • Medusozoa also possess a balancing receptor organ termed a statocyst or statolith, composed of calcium sulphate semihydrate.
  • Medusozoa mostly belong to benthic environments, coastal shores with deep water.
  • Medusozoa can thrive in all oceans and can survive in moderate environmental conditions worldwide.
  • Medusozoa are divided into four classes- Hydrozoa (Hydra), Scyphozoa (true jellyfish), Cubozoa (box jellyfish), and Staurozoa (stalked jellyfish).
  • Medusozoa also develop their colony in Southwestern Atlantic and other nearby regions.

Let us discuss the types, habitats, lifecycle and other essential facts related to Medusozoa in this article.

Types of medusozoa


Hydrazoans are exclusively marine. They are mostly colonial and spend their whole life in the polyp stage. They are sometimes called “fire corals“. They are predatory over zooplankton and other aquatic animals. The body is differentiated into hydrorhiza and hydrocaulus. They have a mouth terminal known as a hypostome.


Scyphozoans are true jellyfish. They are exclusively marine and have a cup-shaped and bright-coloured body structure. They are dimorphic as they exhibit both of the life forms: polyp and medusa. The body cavity is named a coelenteron having some digestive enzymes. They also possess nematocysts for trapping the prey.


The body of cubozoans is cube-shaped and is known as box jellyfish. They also have velum to catch the prey. Tentacles are hanging from all four corners of the organism. They are mostly found in the Indo-pacific region.

Image Credits: Box jellyfish by Rickard Zerpe (CC BY 2.0)


Staurozoans are mostly found near shorelines and shallow water bodies. They feed upon the aquaculture of the marine environment. They are commonly known as stalked jellyfish. They have approximately 50 species present on the Earth. They also show an alternation of generation between polyp and medusa.  

Medusozoa habitat

Habitat is where an organism expect to spend its life and reproduce. Let us see the habitat preferred by Medusozoans.

Medusozoa are habitual to warm temperate and tropical regions. Some species live in colonial form while few are chasing in solitary. They can live in both freshwater and marine ecosystems. Group Scyphozoa are capable to live near polar seas worldwide. While Cubozoa is native to the Eastern Tropical Pacific ocean.

Medusozoa Life Cycle

The life cycle of an organism can be monomorphic, dimorphic, polymorphic or metamorphic. Let us see what type of lifecycle medusozoans perform and survive too.

  • Medusozoans are dimorphic, as most species of this group show dimorphism during their lifecycle.
  • Medusozoa exhibit two life forms in their whole life span, that is, polyp and medusa.
  • Some species of medusozoa exhibit only one phase i.e., polyp, shown by Hydra and other sea anemones of hydrozoan. While all other jellyfish exhibits both life stages.
  • The body of medusozoa is differentiated into two parts: one is a horizontal branch attaching to the substratum while the other one is a freely vertical branch that gives a tree-like appearance, which is named hydrorhiza and hydrocaulus respectively.
  • Hydrocaulus is the part transformed into polyp also known as hydranths, then to blastostyle which contains gonangium.
  • Blastostyle further develops into medusa buds and it starts over again. They also exhibit the power of regeneration.
Image Credits: Jellyfish by Bernard Spragg. NZ (CC0 1.0)

Medusozoa facts

Medusozoans are lower invertebrates belonging to the phyla Coelenterata lately known as cnidaria. Let us discuss some interesting facts related to medusozoans.

  1. Medusozoans colony is whitish, and brown in appearance and has both mobile and sessile forms.
  2. Gonangium contains- gonopore, gonotheca and gonostyle.
  3. Medusozoa show metagenesis. Hydranths include the mouth, hypostome and hydrotheca.
  4. The mouth of medusozoa is covered with tentacles and stinging organs.
  5. Medusozoa have a thin, elastic skin-like structure in between ectoderm and endoderm termed mesoglea.
  6. Planula larvae are found in some species of cnidarians like Obelia.
  7. Medusozoans can also show agamogenesis by budding as in Hydra.
  8. Linthocyte, statocysts or tentaculocysts are receptor organs in medusozoa that also helps in balancing during swimming.
  9. Members of the order-Siphonophora show maximum polymorphism. An example is Hydractinia which is a polymorphic having 5 polyp forms.
  10. Some species of medusozoa also shows trimorphism i.e., polyp, blastostyle and medusae.
  11. Other examples are- Phyllorhiza punctata, Carybdea branchi, Physalia physalis, Polypodium hydriforme, Cerianthus filiformis, Gorgonia ventalin, Acropora muricata etc.

Medusozoa sting

Medusozoans have a sting to capture and inject their prey to get nutrition i.e., they are carnivorous. Let us see what type of stingers medusozoans use.

Nematocysts or cnidocysts are the stinging structures in medusozoa produced from golgi apparatus as a secretory product. It is a specific organ that has barbs and threads to trap and inject the venom inside the body of hosts. These are also used in defence from predators.

Nematocysts are hair-like structures having neurotoxin 1 which is used to take over and unconscious the prey. They are the mechano-chemo receptor which acts on crustaceans by penetration of the ectodermal tissues via the triggering mechanism.


Medusozoans are the smaller carnivorous organisms found in both marine and freshwater environments. They have two phases in life, polyploid and medusoid representing the alternation of generation. They possess a stinging organ, bound with tentacles called cnidae or nematocysts.

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