Give a brief account of Hydrozoan corals 

Give a brief account of Hydrozoan corals 

Life Cycle: Hydrozoans typically have a complex life cycle that involves two main stages: a polyp stage and a medusa stage. The polyp is the primary, sessile (attached) stage, while the medusa is a free-swimming, often umbrella-shaped stage.
Colonial Form: Many hydrozoan corals are colonial, meaning that individual polyps are interconnected and share a common exoskeleton. This results in the formation of colonies that can vary in size and shape.
Skeleton: The skeletons of hydrozoan corals are typically composed of chitin, a complex sugar. Unlike the stony corals (scleractinians) that build reefs in tropical seas, hydrozoans usually do not contribute significantly to reef formation.
Habitat: Hydrozoan corals are found in various marine environments, ranging from shallow coastal waters to deeper oceanic zones. They can be found attached to substrates like rocks or other hard surfaces.
Feeding: Like other cnidarians, hydrozoans have specialized cells called cnidocytes that contain stinging structures called nematocysts. These cells are used for capturing prey, mainly small planktonic organisms. The tentacles around the mouth of the polyp are equipped with these stinging cells.
Reproduction: Hydrozoans reproduce both sexually and asexually. Asexual reproduction often involves budding, where new polyps develop as outgrowths of the original polyp. Sexual reproduction involves the release of gametes (sperm and eggs) into the water, leading to the development of a free-swimming medusa stage.
Ecological Importance: While hydrozoans are not major contributors to reef formation like stony corals, they play a role in marine ecosystems by providing habitat and food for various organisms. 
Millepora: Millepora is a genus of hydrozoans that are known as fire corals or stinging corals. They are found in tropical and subtropical waters around the world, and they grow in a variety of habitats, including coral reefs, shallow waters, and the deep sea. Millepora have a skeleton that is made of calcium carbonate, and they form branching structures that can be up to several meters in diameter.
Stylaster: Stylaster is a genus of hydroids that are known as lace corals. They are found in tropical and subtropical waters around the world, and they grow in a variety of habitats, including coral reefs, shallow waters, and the deep sea. Stylaster have a skeleton that is made of calcium carbonate, and they form delicate, branching structures that can be up to several centimeters in diameter.
Distichopora: Distichopora is a genus of hydroids that are known as feather corals. They are found in shallow tropical and subtropical waters around the world, and they grow in a variety of habitats, including coral reefs, lagoons, and estuaries. Distichopora have a skeleton that is made of chitin, and they form delicate, branching structures that can be up to several centimeters in diameter.