Kinorhyncha characteristics |
Short and worm-like |
Bilaterally symmetrical |
A body divided into 13 or 14 segments |
Each segment of the epidermis has a ventral and dorsal spiny cuticle |
A retractable stylets (piercing mouthpart) |
Muscular pharynx |
An alimentary system with posterior anus |
A pseudocolomic hydrostatic skeleton |
Circular and diagonal muscles |
Nervous system and ventral nerve cord |
Marine |
Sexes separate |
Greek: kinema = motion, rynchos = snout
About 100 species have so far been described, all less than 1 mm long. The most characteristic feature is the segmented, chitinous, spiny cuticle (see Echinoderes sp. above). They are usually found burrowing through mud and silt in shallow waters. They burrow by everting a retractable stylets that has spines towards the end; these attach to the surrounding sediment allowing the animal to drag its body along. The stylets is everted by the pressure exerted when the muscles flatten the body by pulling the dorsal and ventral plates together. The head can be retracted into the trunk leaving just the ring of spiny protective plates. They feed on diatoms and edible particles found in the sediments while burrowing.