Parapodium

Parapodia are predominantly found in annelids, where they are paired, unjointed lateral outgrowths that bear the chaetae.

Most species of polychaete annelids have paired, fleshy parapodia which are segmentally arranged along the body axis.

Parapodia vary greatly in size and form, reflecting a variety of functions, such as gas exchange, anchorage, protection and locomotion.

Both neuropodia and notopodia may possess a bundle of chaetae (neurochaetae and notochaetae respectively), which are highly specific and greatly diversified.

A single stout internal chaeta, called an acicula, may be present in each lobe, which are used to support well-developed parapodia.

Specimen of the annelid, Lepidonotus oculatus , with a microscope image of one of its parapodia (inset). Museums Victoria specimen.
An image plate showing the different anatomical features (dashed outline) of a representative annelid parapodium. Parapodium is from Lepidonotus oculatus and is a Museums Victoria specimen.
Microscope photograph of a parapodium from a specimen of Arctonoe sp. showing the internal acicula that support the two lobes of the parapodium. This parapodium is from a Museums Victoria specimen.
Dorsal view of a freshly collected intact sea slug, Plakobranchus ocellatus , showing its head, rhinophores and parapodia.