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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.
The worm has 21 segments and 16 of them bear chaetae (the bristled setae of polychaetes). The face is somewhat flattened. The body is cylindrical, but tapers slightly toward the posterior end. In life, the worm is transparent, with ring-shaped integument (scaly ridges) along the back, and discontinuous brown stripe markings.
In most species the edge of the mantle also bears movable bristles, often called chaetae or setae, that may help defend the animals and may act as sensors. In some brachiopods groups of chaetae help to channel the flow of water into and out of the mantle cavity.
The third segment has a large lobe that obscures the second segment. Posterior to these, the thoracic region consists of seventeen segments and is cylindrical and firm. There are glandular pads on the ventral sides of segments 14 to 20 which bear both hair-like and hooked chaetae. The long, slender abdomen is soft and bears only hooked chaetae.
Another difference is that, though Therevidae commonly have fluffy setae above the mouthparts, the setae are not stiff bristles like the protective chaetae comprising the mystax of most species of Asilidae.
Depending partly on their form and function, setae may be called hairs, macrotrichia, chaetae, or scales. The setal membrane is not cuticularized and movement is possible. Some insects, such as Eriogaster lanestris larvae, use setae as a defense mechanism, as they can cause dermatitis when they come into contact with skin. [5]
Females measure ~1 mm long and have simplified bodies containing six segments, a reduced coelom, and no appendages, parapodia, or chaetae. The males are only 50 μm long and consist of just a few hundred cells. They lack a digestive system and have just 68 neurons, and only live for roughly a week. [17] [18]
The Naruto manga series, written and illustrated by Masashi Kishimoto, is split in two parts to divide the storyline; the second part is simply known as Part II. [1] [2] The plot follows the return of the ninja Naruto Uzumaki to Konohagakure, after two and a half years of training after leaving his teammates Sakura Haruno and Kakashi Hatake, and his subsequent efforts to make his best friend ...