Pseudocoelomates

Definition

Pseudocoelomates are animals that possess a pseudocoel, a fluid-filled body cavity between the mesoderm and endoderm layers. This cavity is not fully lined by mesodermal tissue, distinguishing them from true coelomates.

5 Must Know Facts For Your Next Test

1. Pseudocoelomates include organisms like nematodes and rotifers.
2. The pseudocoel functions as a hydrostatic skeleton to support the body and aid in movement.
3. Pseudocoelomates have a complete digestive system with a mouth and an anus.
4. The pseudocoel allows for the distribution of nutrients and waste removal within the organism.
5. Pseudocoelomates exhibit bilateral symmetry, meaning their body can be divided into mirror-imaged halves.

Review Questions

• What is the primary difference between coelomates and pseudocoelomates?
• Name two examples of organisms that are considered pseudocoelomates.
• How does the pseudocoel benefit the movement and support of these organisms?

Related terms

Coelomates: Animals with a true coelom, a body cavity completely lined by mesodermal tissue.

Acoelomates: Animals that lack a body cavity between the digestive tract and outer body wall.

Hydrostatic Skeleton: A structure found in many soft-bodied animals consisting of a fluid-filled cavity surrounded by muscles.