Urochordata & Cephalochordata:

Energy & Mode of Nutrition

Energy & Mode Of Nutrition: The Cephalochrodate

A cephalochordate is able to trap food particles through a mucous net that is secreted across its pharyngeal slits.  First, the cephalochordate draws sea water which contains small food particles into its mouth by ciliary pumping (Bellarmine).  Next, the water exits through the pharyngeal slits and the food passes through the digestive tube.  Small particles in the water are trapped by the cilia in different parts of the mouth chamber and separated into edible and waste material (Paisley).

Energy & Mode Of Nutrition: The Urochordate 

Urochordates, like cephalochordates, attain their food from sea water.  Sea water enters a urochordate through the pharyngeal slits and passes into a chamber called the atrium.  Food particles are filtered by a mucus net and cilia pass through these particles into the intestine.  Sea water exits through the excurrent siphon or atriopore of the urochordate.  A "cellulose-like carbohydrate" known as tunic (the name-sake of tunicates!) envelopes the urochordate body (Campbell et al. 1999).  While water and suspended plankton are drawn through the incurrent siphon into the pharynx, organic particles are strained from the water by the pharyngeal gill slits and trapped in mucus at the base of the pharynx (Bellarmine).  With help of the cilia, the food-mucus mixture is moved to the stomach and digestion begins (Bellarmine). While this is occurring, the filtered water passes from the pharynx to the atrium and out the excurrent siphon (Bellarmine). A body wall lining the body of the urochordate aids in respiration (Lundburg 1995). 

The Urochordate Digestive System

 (permission granted) 

http://cas.bellarmine.edu/tietjen/images/urocho18.jpg 

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