Defining Characteristics ¹

Chaetognaths are a dominant part of the plankton, outnumbered only by copepods. Chaetognaths are transparent and shaped like a torpedo or arrow; hence the common name "arrow worms."

Feeding ¹

These worms are predators of copepods, larval fish, crustaceans, and other chaetognaths. Using grasping spines found on either side of the head, chaetognaths can grab and ingest very large organisms. The arrow worms use mechanoreceptors that sense water movements to help detect other organisms, and some species have a specialized venom in the head region that helps to subdue captured prey.

Locomotion ¹

When chaetognaths swim they cover their grasping spines with a hood, making them more streamlined and allowing for faster movements. Swimming in chaetognaths is accomplished by bending the head region back towards the tail in a flicking movement which cause the sleek worm to glide forward. Fins are also important in the organism’s locomotion. Posterior fins are used to overcome sinking and facilitate stabilization of the swimming motion. The tail fin may help to rocket the organism through the water.

Habitat ²

Although widely distributed, arrow worms prefer warm, shallow seas and are particularly plentiful in the Indo-Pacific region.

Other Information ¹

Besides being active predators themselves, chaetognaths are an important food source for fish and other marine animals. It is believed that chaetognaths use their mechanoreceptors to follow the vertical migration of prey, that is their daily movement up or down in the water column.

Chaetognatha Links

1. http://depts.washington.edu/fhl/zoo432/plankton/plchaetognatha/chaetognatha.html

2. http://www.bartleby.com/65/ch/Chaetogn.html

Defining Characteristics 1

Feeding 1

Locomotion 1