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How does the digestive tract of a bryozoan zooid work?
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moss animal
Eurystomella bilabiata, a moss animal from the Order Cheilostomata.
The digestive tract of a bryozoan zooid is organized into a deep, U-shaped loop that facilitates efficient processing of food particles. The process functions as follows:1
- Ingestion: Food particles are captured by the ciliated tentacles of the lophophore and directed toward the mouth. From there, particles are sucked into the pharynx.2
- Processing: In some genera, such as the gymnolaemate Bowerbankia, the anterior portion of the stomach functions as a gizzard to break down or separate diatom shell valves.12
- Digestion and Absorption: The primary digestion and absorption of nutrients occur within the stomach.2
- Waste Removal: Indigestible remains are compacted by rotation into fecal pellets and expelled through the anus. Notably, the anus is situated just outside the lophophore, which is why these organisms are sometimes referred to as Ectoprocta, meaning "outside anus".13
Nutrients are distributed throughout the colony via the funiculus, a cord of tissue linking the stomach to the body wall lining.1