Details of Urochordata Essay Sample
- Pages: 2
- Word count: 496
- Rewriting Possibility: 99% (excellent)
- Category: blood
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Introduction of TOPIC
Urochordata is one of the sub phylum of chordate. Tunicates or Urochordata are all marine and colonial or solitary. Some species lead a sedentary life and others are pelagic. The Ascidian tunicate has formed a wrinkled cylinder or sac with 3-4 inches in length and has a broader base by which the organism is attached to the rocks or other substrates. Large aperture is present at the free end that is more or less terminal position which is the mouth or the inhalant siphon. Atrial or exhalent aperture is present little behind the aperture. Water current flows into the organism by the mouth and passes out through the atrial aperture. Disturbing of the animal makes it to squirts out jets of water through the atrial aperture and this gave the organism the name sea squirt. Anterior end of the animal is made by the oral aperture and posterior end is attached to the substrates and in the dorsal position the atrial aperture is placed.
The body of the animal is enc
losed into a tough tunicine, a substance made of cellulose. The underlying ectoderm of the body wall
Mouth leads to the short stomodaeum that is formed by the infolding of the ectoderm. Stomodaeum is followed by the pharynx which occupies the major part of the body from mouth to base. These regions are covered by the atrial or peribranchial cavity and all these parts are enclosed by the mantle. Long the mid ventral line the pharynx is attached to the mantle and free at the dorsal and lateral parts. Atrial aperture is an exterior opening for the atrial cavity. Pharynx is a food collecting apparatus and the animal feeds on small organisms which come into the mouth along the water current. The pharynx is perforated by numerous gill silts or stigmata and the lining of pharynx and edges of the stigmata are ciliated. There is a ciliated groove in the inner median line called as the endostyle. Respiration takes place by the passing of water through the stigma. The transverse and vertical region of the pharyngeal region contains blood vessels.
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