Phylum Chaetognatha ( Arrow Worms )

BIOLOGY 2Presented by:

Dan Michael D. PabilonaBEED-3D3

Presented to:Ms. Earma G. Padilla

Instructor, Biology 2

March 09, 2017

PHYLUMCHAETOGNATHA

General Description Mode of Nutrition Reproduction Locomotion Habitat Classification

The name Chaetognatha (ke-tog-na-tha) comes from the Greek word

( Chaite – means long flowing hair, + Gnathos – means Jaw)

Chaetognatha

Phylum Chaetognatha meaning Bristle-jaws.

- commonly known as “arrow worms”. Are coelomate animals of relatively small size, with straight, slender, transparent body displaying perfect bilateral symmetry.

* they are usually colorless, slightly opaque.

General Description

* the body is divided in three parts by internal partitioning: HEAD, TRUNK and TAIL.- Fins on both the tail and the body.

- The head has eyes with photoreceptive cells, Each side of the head bears a group of curved grasping hooks and one or two rows of teeth.

* called the anterior and posterior teeth.

* the hooks and teeth are made of chitin.- The trunk bears one or two pairs of lateral fins incorporating structures superficially similar to the fin rays of fish, with which they are not homologous.

- They are generally less than an inch (2.5 centimeters) in size.

Chaetognaths are carnivorous predators.

These voracious meat-eaters catch large numbers of copepods, larval fish, crustaceans, swallowing them whole.

- The large spines around their mouth helps them grab and restrain their prey and immobilize them with neurotoxins.

Mode Of Nutrition

All known Chaetognatha are Hermaphrodites.

* meaning they possess both male and female sex organs.

- The female organ ( the ovaries)

* are just behind the mid-body mark (trunk)

- The male organ ( the testis)

* are in the tail

Reproduction

The sperm mature before the ova (eggs) which may help avoid self fertilization to same extent.

Fertilization is internal and depending on the species fertilized eggs may be brooded, deposited on the seafloor, or released into the ocean.

Their torpedo-like body shape allows them to move quickly through the water.

- Chaetognatha alternate between swimming and floating.- The fins along their

body are not used to swim, but rather to help them float.

- They usually swim to the surface at night and descend during daytime.

Locomotion

They are found in all marine waters, from surface tropical waters and shallow tide pools to the deep sea and polar regions, most species are planktonic, but a small number of species are Benthic.

* about 20%, live just above the ocean floor and can attach to seaweed or rocks.

Habitat

Chaetognatha are traditionally classed by an (embryologist) as Deuterostomes and by (phylogenists) as Protostomes.

Classification Kingdom: Animalia

Phylum: Chaetognatha

Class: SagittoideaOrder:

Aphragmophora

Phragmophora

The embryologist Lynn Margulis and K.V Schwartz placed chaetognaths in deuterostomes in their five kingdom classification.

Deuterostomes - The name deuterostomes means "second mouth." The name is derived from the embryo developing the anus first, followed by the mouth.

The phylogenists Thomas Cavalier- Smith placed them in the protostomes in his six kingdom classification.

Protostomes – means “first mouth” embryos develop the mouth first and then the anus,

Reference• Animaldiversity.org/accounts/chaetognatha• www.earthlife.net/inverts/chaetognatha.html• www.newworldencyclopedia.org/entry/Chaetognatha• https://en.Wikipedia.orh/wiki/Chaetognatha• eol.org/pages/1740/overview• Species-identification.org• www.polarlife.ca/organisms/inverts/marine_inverts/chaet

ognatha.htm