Checklist of chaetognatha phyllum from São Paulo State, Brazil

Abstract

The species of Chaetognatha, commonly called arrow-worms, are considered one of the most taxonomically isolated animal groups, with obscure phyletic origin. They are deuterostomes of small size, between 2 and 12 mm, with bilateral symmetry and transparent torped-shaped body, although some species have pigmentation. The body consists of the head, the trunk and the tail. The head bears a ventrally placed mouth, surrounded by two sets of rigid hooks and rows of small teeth, both used in prey capture. There are two dorsal eyes, which are absents in some deep living species. The trunk bears paired lateral fins and the tail a single fin. They are protandrous hermaphrodites with direct development, being the cross-fertilization probably typical in this phylum. Fertilization is internal and the eggs released directly into the water. Although chaetognaths are eaten by numerous larger carnivorous organisms, in the food web they are important predators and a significant trophic link between small herbivores and larger predators, including important commercial fish species. Cannibalism is known, particularly in some species. They have been recognized as important producers of large quantities of fecal pellets, which must play a significant role in the flux of organic carbon in the oceans. Chaetognaths are also considered good indicators of potentially important fishery areas, and more recently, they gained recognition as vectors in the life cycles of various parasite groups. They are exclusively marine and can be found in all oceans from surface to great depths and in estuarine regions. Generally are most abundant around 100-200 m depths. With exception to the epibenthic family Spadellidae, the chaetognaths are conspicuous members of the zooplankton. Their distribution pattern is influenced by the hydrobiological conditions and some species are known as indicators of water masses. A total of 209 species were recorded in the world's oceans, and 29 for the South Atlantic. Twenty five species are known from the Brazilian waters and only 14 species from coastal and offshore waters of São Paulo State.