Chaetognaths are transparent or translucent dart-shaped animals covered by a cuticle. They range in length between … Meer weergeven

All species are hermaphroditic, carrying both eggs and sperm. Each animal possesses a pair of testes within the tail, and a pair of ovaries in the posterior region of the main body cavity. Immature sperm are rele… Meer weergeven

Little is known of arrow worms' behaviour and physiology, due to the complexity in culturing them and reconstructing their natural habitat. It is known that they feed more frequently with higher temperatures. Plan… Meer weergeven

Chaetognaths are found in all world's oceans, from the poles to tropics, and also in brackish and estuarine waters. They inhabit very diverse environments, from hydrothermal vents to deep ocean seafloor, to s… Meer weergeven

The mtDNA of the arrow worm Spadella cephaloptera has been sequenced in 2004, and at the time it was the smallest metazoan mitochondrial genome known, being 11,905 base pairs long (it has now bee… Meer weergeven

The evolutionary relationships of chaetognaths have long been enigmatic. Charles Darwin remarked that arrow worms were "remarkable for the obscurity of their affinities". Chaetognaths in the past have bee… Meer weergeven

Due to their soft bodies, chaetognaths fossilize poorly. Even so, several fossil chaetognath species have been described. Chaetognaths first appear during the Cambrian Period. Complete body fossils hav… Meer weergeven