Checklist do filo Chaetognatha do Estado de São Paulo, Brasil

Abstract

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. Resumo: O filo Chaetognatha é constituído de um pequeno número de animais marinhos deuterostomados, filogeneticamente isolados, de simetria bilateral e corpo alongado em forma de torpedo ou seta, cujo comprimento pode variar de 2 a 120 mm. O corpo é dividido em três regiões: cabeça, tronco e cauda. A cabeça apresenta um par de olhos e a boca situada no vestíbulo ventral, a qual é circundada por uma coroa de espinhos fortes e por uma ou duas fileiras de dentes. O tronco possui um ou dois pares de nadadeiras laterais e a cauda uma nadadeira na extremidade posterior. São hermafroditas protândricos sendo em geral a fecundação cruzada, interna, e o desenvolvimento direto. São predadores que se alimentam de uma grande variedade de organismos. O canibalismo também é observado no grupo. Os quetógnatos desempenham papel fundamental na teia trófica marinha, como carnívoros primários e item alimentar de organismos planctófagos especialmente peixes de interesse comercial. São considerados bons indicadores de áreas de pesca, potencialmente importantes, grandes produtores de matéria orgânica particulada e peça chave no fluxo do carbono nos oceanos. Mais recentemente, foram reconhecidos como hospedeiros intermediários no ciclo de vida de vários grupos de parasitas marinhos. Os quetógnatos são encontrados em todos os mares, oceanos e regiões estuarinas, sendo mais abundantes entre os 100 e 200 m de profundidade. Com exceção dos componentes da famíl...

Genetic diversity and connectivity of Flaccisagitta enflata (Chaetognatha: Sagittidae) in the tropical Atlantic ocean (northeastern Brazil)

“…However, a lifetime of this order should allow F. enflata transiting between oceanic waters and the Brazilian coast. The observation of continuous reproductive cycles over the whole year, a common feature of Chaetognatha species [5], would further contribute to its dispersion in the evaluated areas.…”

“…Chaetognaths are assiduous zooplankton predators, food items of a wide variety of taxa and producers of particulate organic matter [3,4]. All species are hermaphrodites [5] and the life cycle of a large part of the group is holoplanktonic with direct development [1,5], where from the hatching of the eggs emerge individuals very similar to adults with regard to body organization. The lifetime is variable and known for a few members of the phylum, with a maximum estimate of approximately 15 months for a species investigated in shelf waters of the Atlantic Ocean [6].…”

Characterization of the zooplankton in the continental shelf of the Brazilian Equatorial Atlantic

“…The phylum Chaetognatha was the second most representative in terms of number of species (seven species). This phylum is characterized by the predominance of marine species and predators of the pelagic community (mainly Copepoda), with considerable influence on the structure of this group (Pearre, 1980;Vega-Pérez and Schinke, 2011). According to Boltovskoy (1999), Parasagitta tenuis and Flaccisagitta enflata are the most frequent Chaetognatha on the Brazilian coast due to their eurythermal and euryhaline characteristics, and they may also occur in neritic waters.…”