Chaetognatha

Chaetognatha , phylum of predominantly pelagic marine animals commonly known as arrowworms. Arrowworms have slender, transparent bodies, usually under 1 in. (2.5 cm) long. Lateral and caudal fins propel the animal in sudden darting movements. The well-developed head bears eyes and other sense organs, grasping spines used in the capture of prey, and rows of teeth flanking the mouth. A protective hood can be folded down over the bristles and teeth. The digestive system includes a glandular pharynx, a straight intestine, and a short, muscular rectum. The nervous system centers in a bilobed, dorsal brain and several other nerve ganglia. Although widely distributed, arrowworms prefer warm, shallow seas and are particularly plentiful in the Indo-Pacific region. They are voracious predators; some feed on freshly hatched fish nearly as large as themselves. They are influential planktonic consumers when abundant.

Chaetognatha Phylum comprising the arrow worms, first encountered in the fossil record in Carboniferous rocks.

Chaetognatha A phylum of marine coelomate invertebrates, the arrow worms, in which the head bears hooks for catching prey and the trunk and tail support paired lateral and tail fins. They lack organs for excretion, circulation, and respiration and are hermaphrodite.