Kinorhynchs: Kinorhyncha

Kinorhynchs (KIH-nuh-rinks) are tiny, spiny worms that live in the sea. Adult kinorhynchs are 0.008 to 0.05 inch (200 micrometers to 1.2 millimeters) long. Most kinorhynchs are clear, but some are yellowish or reddish. Kinorhynchs have 13 body segments: a head, a neck, and 11 trunk segments. The head is spherical, can be drawn into the trunk, and has 5 to 7 rings and as many as 91 spines that face backward. The mouth, which is at the tip of the head, contains sharp teeth and is surrounded by bristles. There are more bristles inside the mouth. The head is joined to the trunk by a neck that has plates that close over the head when it is pulled back into the trunk. The trunk is covered by armor and spines and contains glands that release mucus.