Anthozoa

Definition

Anthozoa is a class of marine invertebrates within the phylum Cnidaria, comprising organisms such as sea anemones and corals. These creatures are characterized by their polyp form, which is the only stage in their life cycle, and they exhibit a wide range of shapes, colors, and sizes. Anthozoans are crucial to marine ecosystems as they contribute to reef-building processes and provide habitats for various marine life.

5 Must Know Facts For Your Next Test

1. Anthozoans have a unique life cycle that consists solely of the polyp form, unlike other cnidarians that also exhibit a medusa stage.
2. Many anthozoans engage in symbiotic relationships with zooxanthellae, photosynthetic algae that live within their tissues, providing them with nutrients and vibrant colors.
3. Coral reefs formed by anthozoans are among the most diverse ecosystems on the planet, supporting approximately 25% of all marine species.
4. Anthozoans can reproduce both sexually and asexually; asexual reproduction often occurs through budding or fragmentation.
5. Climate change and ocean acidification pose significant threats to anthozoans and coral reefs, leading to bleaching events and reduced calcification rates.

Review Questions

• How do anthozoans contribute to marine ecosystems, particularly through their relationship with coral reefs?
  • Anthozoans play a vital role in marine ecosystems by forming coral reefs, which are essential habitats for many marine species. These structures provide shelter and breeding grounds for fish and other organisms while supporting biodiversity. The calcium carbonate skeletons secreted by coral polyps contribute to the growth and maintenance of these reefs, creating complex environments that foster various forms of marine life.
• Evaluate the ecological significance of the symbiotic relationship between anthozoans and zooxanthellae.
  • The symbiotic relationship between anthozoans and zooxanthellae is ecologically significant as it enhances nutrient acquisition for both parties. The zooxanthellae perform photosynthesis, providing the anthozoans with organic compounds for energy. In return, the anthozoans offer protection and access to sunlight for the algae. This partnership is crucial for the survival of many coral species, particularly in nutrient-poor waters, and contributes to the overall productivity of coral reef ecosystems.
• Analyze the impacts of environmental changes on anthozoans and the broader implications for marine biodiversity.
  • Environmental changes such as climate change and ocean acidification have significant impacts on anthozoans, primarily through coral bleaching and decreased calcification rates. When water temperatures rise or when the pH of oceans decreases, zooxanthellae are expelled from coral tissues, leading to bleaching. This phenomenon reduces the survival rates of corals, ultimately affecting the biodiversity supported by coral reefs. The decline in reef health not only threatens various marine species but also disrupts ecosystem services like coastal protection and tourism, highlighting the interconnectedness of environmental health and marine biodiversity.

Related terms

Cnidaria: A phylum of animals that includes jellyfish, corals, and sea anemones, characterized by their radial symmetry and specialized stinging cells called cnidocytes.

Polyp: A sessile life stage of certain cnidarians, including anthozoans, characterized by a cylindrical body with a mouth surrounded by tentacles.

Coral Reefs: Underwater structures made from calcium carbonate secreted by coral polyps, providing essential habitats for countless marine species.