AMPHIOXUS LANCEOLATUS - created from Mind Map

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Burrowing form

During night, and breeding season, it comes out from the sand and swims freely.

its active larval forms and young ones are pelagic

Fish like animal

it looks like a fish.

its both ends are sharp.

But it is different from a fish, in the absence of jaws, paired fins, scales etc.

FINS

Epipleur

Anterior two third portion of body is a flat and ridged area called epipleur.

Metapleural folds

Atrial folds

Lateral edges of epipleural have hollow projecting ridges

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Posteriorly, 2 metapleural folds meet together in the mid ventral line.

Atriopore

Opening in the anterior terminal region of ventral fin

it is the external opening of the internal cavity called atrium.

Olfactory pit

Near the anterior tip of the body on left dorsal side ,is a small pit

PRE ORAL PIT

KOLLIKER"S PIT

Vestibule

Stomadaeum

Funnel shaped depression

3) caudal fins

dorsal fins turns round the posterior end of the body as caudal fins.

1) Paired fins

Abscent

2) dorsal fins

Extends along the whole length of the mid-dorsal border.

4) ventral fins

caudal fins runs forward, along the mid-ventral line upto the anterior two third of the body as ventral fins.

Oral Hood

surrounds the vestibule

Frill like membrane

Bears the mouth

Velum

On the bottom of the vestibules, is

a circular sphincter.

Hatschek's Groove

Hatchek's pit

on the roof of vestibule

Grandular mucus secreting groove

Oral cirri

Edges of oral hood are frilled with a series of ciliated membrane called oral cirri

buccal cirri

Wheel organ

Epithelial lining on the inner side of the oral hood is thrown into a system of ciliated ridges and grooves, called wheel organ.

Organ of muller

The movement of its cilia create a whilring current of water during feeding.

Enterostome

in the centre of velum, a circular aperture called enterostome is present

Velar tentacles

Around the enterostome, is a series of ciliated tentacular processes called velar tentacles.