Chaeta

A chaeta or cheta (from Ancient Greek χαίτη (khaítē) 'crest, mane, flowing hair'; pl.

chaetae) is a chitinous bristle or seta found on annelid worms, although the term is also frequently used to describe similar structures in other invertebrates such as arthropods.

Spines are also common but are thicker and stouter than capillaries and may be curved or straight and can be distally dentate (e.g. unidentate or bidentate).

Furcate (also called comb, forked or brush) chaetae are similar to capillaries for most of their length but expand distally into a flattened comb- or fork-like tip.

Uncini are highly modified chaetae in which the shaft is reduced (or virtually absent) and the tip is broadened to create short, stout structures.

Specimen of the annelid, Lepidonotus oculatus showing its chaetae projecting laterally, with a microscope image of one of its parapodia and chaetae (inset). Museums Victoria specimen.
Microscope photograph of a parapodium from a specimen of Arctonoe sp. showing the chaetae and internal acicula. This parapodium is from a Museums Victoria specimen.