What does the name Chaetognatha mean?

The Chaetognatha or chaetognaths (meaning bristle-jaws) are a phylum of predatory marine worms that are a major component of plankton worldwide. Commonly known as arrow worms, about 20% of the known Chaetognatha species are benthic, and can attach to algae and rocks.

Is Chaetognatha a Holoplankton?

Chaetognaths belong to an exclusively marine phylum commonly known as arrow worms. There are around 100 species in the phylum, of which 10 are known from south-east Australian waters. They are mostly holoplanktonic predators on copepods and other crustaceans but there are a few benthic forms.

Is chaetognaths Triploblastic?

Triploblastic relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: a combined approach of 18S rDNA sequences and morphology.

Are arrow worms Holoplankton?

Arrow worms are zooplankton, small animal plankton (drifters of the sea). Unlike many zooplankton, which may be the young stage of familiar reef animals such as fish, seastars or even corals, arrow worms are holoplankton, they stay the same and remain plankton for their entire life.

How do chaetognaths move?

It is believed that chaetognaths use their mechanoreceptors to follow the vertical migration of prey, that is their daily movement up or down in the water column. When chaetognaths swim they cover their grasping spines with a hood, making them more streamlined and allowing for faster movements.

Which organisms are members of the Holoplankton?

Examples of holoplankton include some diatoms, radiolarians, some dinoflagellates, foraminifera, amphipods, krill, copepods, and salps, as well as some gastropod mollusk species.

Is phytoplankton a Meroplankton?

Meroplankton are plankton for only part of their lives (usually the larval stage). Holoplankton are plankton for their entire lives. They can be either phytoplankton or zooplankton. One well-known example of this is the Portuguese Man-of-War.

Which type of worm is a planktonic Carnivore?

The Chaetognatha /kiːˈtɒɡnəθə/ or chaetognaths /ˈkiːtɒɡnæθs/ (meaning bristle-jaws) are a phylum of predatory marine worms that are a major component of plankton worldwide.

How do chaetognaths reproduce?

Reproduction in chaetognaths is unique. All chaetognaths are hermaphroditic, meaning they have both male and female parts. During the courtship the sperm must rupture through an outpocketing of the body and travel down along the partners body into the female opening.

Why is the phylogenetic placement of chaetognaths uncertain?

Problems arise because of the lack of morphological and physiological diversity within the group. In addition, no unambiguous chaetognaths are preserved as fossils, so nothing about this groups evolutionary origins can be learned from the fossil record.

Which organisms are members of the holoplankton?

What are the two orders of chaetognathas?

The phylum contains two orders, Phragmophora and Aphragmophora. The main difference between the two is the presence of ventral transverse muscle bands in Phragmophora, which are absent in Aphragmophora. Chaetognaths may be found in marine and some estuarine environments throughout the world.

What kind of worms are in the Chaetognatha phylum?

The phylum Chaetognatha, also known as arrow worms, contains nearly 200 species of mostly planktonic, bilaterally symmetrical, coelomate, worm-like organisms. The phylum contains two orders, Phragmophora and Aphragmophora.

What kind of body does a Chaetognatha have?

Chaetognaths range from 1 mm to 12 cm in length and are typically transparent, although some deep-water species may be orange in color (carotenoid pigmentation), and phragmophorids may be opaque, due to their musculature. They are bilaterally symmetrical and have long, streamlined bodies, which may be divided into head, trunk, and tail regions.

Where can chaetognaths be found in the ocean?

Chaetognaths are mainly planktonic organisms in marine and estuarine environments. About a fifth of the total species are benthic, some living just above the deep ocean floor. They are often found in great numbers, particularly in mid-water and neritic waters, and may be found in rock pools or associated with certain oceanic currents.