Britannica
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How do avicularia differ from ordinary feeding zooids?
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moss animal
Eurystomella bilabiata, a moss animal from the Order Cheilostomata.
In bryozoan colonies, ordinary feeding zooids are equipped with a lophophoreβa ring of ciliated tentacles used to capture planktonic particles for digestion. In contrast, avicularia are specialized, polymorphic zooids that differ significantly in both structure and function.123
Key differences include:
- Structure: Avicularia possess a small body and a rudimentary polypide, lacking the fully developed feeding apparatus found in normal zooids. Their operculum is proportionally much larger and is supported by strong adductor muscles, effectively functioning as a jaw.3
- Appearance: While feeding zooids are typically cylindrical or flat with a tentacle sheath, avicularia are often smaller and may be attached to normal zooids. In some species, such as Bugula, they are movable on stalks and resemble miniature birds' heads.3
- Function: Unlike feeding zooids, which are dedicated to nutrition, avicularia are believed to help maintain the colony by keeping its surface free from debris and other organisms that might otherwise attach to it.3