amphioxus diagram | amphioxus classification

Amphioxus diagram

Amphioxus Classification

The Sub-Phylum has single class Laptocardi. Ex:- Branchiostoma or Amphioxus or Lancelet.

Kingdom	Animalia
Sub-kingdom	Metazoa
Infra-kingdom	Enterozoa
Section	Eucoelomata
Phylum	Chordata
Group	Acrania
Sub-Phylum	Cephalochordata
Class	Leptocardii
Family	Branchiostomidae
Genus	Branchistoma or Amphioxus or Lancelet

Historical Distribution

The animals of Sub-Phylum cephalochordata are small marine and fish like. The three important chordates character Notochord, Nervechord and pharyngeal Gill's Slits through out life. The most important animal of this Sub-Phylum is west known as Branchiostoma or Amphioxus or also called Lancelet. The first time is discovered by poles in 1778.

Scientists Coastal give the animal name as Branchiostoma lanceolatum or Amphioxus lanceolatum. About 9 species of Branchiostoma are known in which some are as Branchiostoma indicum, Branchiostoma pelagicum and Branchiostoma cerrivacum most important which detail discription based on Branchiostoma lanceolatum.

Habit and Habitat

Branchistoma is marine animal commonly found in shallow water specially salt water of sea. Mostly it is burried in sand and only anterior part upright above the sand. At night it comes out of the sand and swim actively. When disturb it jumps out the burrow inside so that anterior and comes out of the sand. Branchistoma is cilliary feeder animal. It's feeds on planktonic micro organism which comes respirative, comes food water current which enters into the mouth. Male and female animal are separate. Fertilization is external takes place in sea water and development is indirect involve free swimming larva.

External features

Shape size and color

Branchistoma is small, elongated, narrow and fish like animal about 5-8 cm in length. The body is whitish transparent and pointed at both end so the name given as Lancelet which means little lens or spear. The body is stream line so we'll maintain by animal for burrowing and swimming. The posterior end is some what broad at anterior end.

Division of body

The body is divided into two region as trunk and tail. The anterior end is trunk and true head absent and posterior region tail. The pointed anteriror end is also called snout or rostrum.

Aperture

In animal the trunk bear three opening as mouth atrialpore and anus. Below the rostrum there is tentaculated Structure the oral hood farmed by lateral end dorsal outgrowths of body. The mouth is vary wide, surrounded by oral hood. The atrial core is small rounded aperture present in front of the ventral fin. The anus is small aperture present at the base of caudal fin.

Fins and folds

Branchistoma has three fins, dorsal, ventral and caudal. The dorsal fin trunk mid dorsal folds of the length of body. It continues behind the caudal fin around the body near the atriopore. It is wider than dorsal fin. Paired find absent but anterior 2/3 part of trunk from oral hood to atriopore there are metaplural fold. The caudal fin present at the posterior and of body it is broader than dorsal and ventral fin.

Myotoms and Gonads

On each lateral side of body there is a series of < - shaped muscle bend called myotoms which also seen through transparent body wall. Between mouth and anterior there present a series of Gonads.