Chaetognath species: pseudo-larval stage
There are approximately 50 species of arrowworms described. They are primarily tropical in nature, but are found in the plankton of all oceans. Although, all but one species are planktonic, there is distinct vertical stratification of species. Many species live only in the upper photic zone (above 200 meters); some are restricted to coastal waters, others appear well off shore where they encounter little salinity fluctuations. Other arrowworms live in depths 200-900 meters deep. Some species undergo seasonal or diurnal migrations between surface and lower depths. The young are called larvae after they hatch, although they are similar in appearance to the adult, and no metamorphosis occurs. (See Barnes, Invertebrate Zoology.) Sample was collected in a net tow offshore of Ft. Pierce, FL.