Anthozoa

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Beryx decadactylus 4

Heteractis malu

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Blackcoral colony 600

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Scheibenanemone

Brain coral

Anthozoa is a class of marine invertebrates belonging to the phylum Cnidaria. This class includes the well-known corals and sea anemones. Anthozoans are characterized by their sessile life, meaning they are permanently attached to the ocean floor, and their unique reproductive and feeding structures. Unlike other cnidarians, anthozoans do not have a medusa stage in their lifecycle; they exist solely as polyps throughout their life.

Characteristics

Anthozoans are distinguished by their radially symmetrical bodies, which are divided into segments. Their bodies are composed of a central digestive chamber, known as the gastrovascular cavity, with a single opening that functions as both mouth and anus. Surrounding the mouth are tentacles that contain cnidocytes, specialized cells that harbor stinging nematocysts used for capturing prey and defense against predators.

The body of an anthozoan is supported by an internal or external skeleton. In corals, this skeleton is typically made of calcium carbonate and forms coral reefs, which are vital to marine biodiversity. Sea anemones, on the other hand, often adhere to rocks or sand with a sticky foot called a basal disc.

Reproduction

Anthozoans can reproduce both sexually and asexually. Sexual reproduction involves the release of eggs and sperm into the water, where fertilization occurs. The resulting larvae, known as planulae, settle on the ocean floor and develop into new polyps. Asexually, anthozoans can reproduce through budding, fission, or by producing genetically identical clones.

Ecology

Anthozoans play a crucial role in marine ecosystems, particularly coral species that form coral reefs. These reefs provide habitat and shelter for a vast array of marine life, including fish, mollusks, and crustaceans. Anthozoans themselves are prey for certain species of fish and sea slugs, and their relationship with symbiotic algae, known as zooxanthellae, is essential for the health of coral reefs. The algae live within the coral tissues, providing the corals with nutrients through photosynthesis, while the corals provide the algae with a protected environment and access to sunlight.

Conservation

Anthozoans, especially coral species, are under threat from climate change, ocean acidification, pollution, and destructive fishing practices. These threats can lead to coral bleaching, where corals lose their symbiotic algae, leading to a decline in coral health and the ecosystems they support. Conservation efforts are focused on protecting coral reefs, reducing pollution, and mitigating the impacts of climate change.