Threatened species of Chaetognatha

A March 3 1995 edition of the journal Science, reported that the population of zooplankton in the waters off the coast of Southern California had declined by 70 percent in the last 42 years. The observed decline may be linked to a warming of the ocean surface in the region over the same time period. Arrow worms and other zooplankton form a vital link near the base of the food chain, a decline in their numbers could pose a threat to other marine life.

Planktonic carnivores seldom exceeding 3 cm long. Also known as "Tigers of the zooplankton" There are 60 species of arrow worms.