Scyphozoan

Scyphozoans, commonly known as true jellyfish, are a class of marine invertebrates belonging to the phylum Cnidaria. They are characterized by their bell-shaped, gelatinous bodies and tentacles that surround the mouth, which is located at the underside of the bell. Scyphozoans are typically free-swimming and exhibit a life cycle that alternates between two distinct phases: the polyp stage and the medusa stage.

The polyp stage is sessile or slow-moving, often attached to substrates such as rocks or coral. It reproduces asexually, producing ephyrae, which are small medusae that detach and develop into mature jellyfish through a process called strobilation. The medusa stage is the dominant, free-swimming phase, where scyphozoans are fully developed and capable of sexual reproduction. Medusae release eggs and sperm into the water, which fertilize externally to form planula larvae.

Scyphozoans are found in nearly all oceans worldwide, from polar regions to tropical seas, though some species are more common in temperate waters. They play a significant role in marine ecosystems, serving as both predators and prey. Many species are known for their striking colors and patterns, ranging from translucent to vibrant hues. Some scyphozoans, such as the box jellyfish, are highly venomous and pose risks to humans.

Environmental factors, including pollution, climate change, and overfishing, can impact scyphozoan populations. Some species have experienced significant population booms, known as jellyfish blooms, which can disrupt marine food webs and affect coastal communities. Conservation efforts are ongoing to better understand and mitigate the impacts of these changes on scyphozoan populations and their ecosystems.