pleosomites

Example:Unlike pleosomites, which are solid support structures added to body segments, vesicles are membrane-bound containers that float within the cytoplasm and have no structural support function.

Definition:Small, fluid-filled sacs or cavities in the body, such as those in the walls of blood vessels that help regulate the exchange of substances between the blood and tissues. Vesicles are fundamentally the opposite of solid structural additions like pleosomites.

Example:In some simple polychaete species, there is an absence of segmentation, unlike more complex species that include pleosomites as additional parts of the body structure.

Definition:The lack of a clear or regular body plan with distinguishable segments, which is the inverse of having specific additional body structures, such as pleosomites, which add to a regular segment pattern.