NUTRITION AND FEEDING MECHANISMS 



213 



long filamentous gill. The gill filaments are attached to the left side of the 

 mantle cavity and extend across it so as to form a continuous membrane. 

 On the sides of the filaments are lateral cilia which create a water current ; 

 this current enters the ventral chamber, passes through the gill, and leaves 

 the dorsal chamber as an exhalant stream (Fig. 5.10a). 



The current entering the mantle cavity passes through a mucus-filter 

 produced by a filter gland. This filter strains out mainly the larger particles, 

 which are carried towards a food pouch near the mouth. Here the particles 



Brachial 

 valve 



Oral disc 

 'on 



ai 

 membrane 



Fig. 5.9. Lophophore and Feeding Currents of the Brachiopod 



Neothyhs lenticularis 



View with pedicle valve removed. The filaments have been cut from one side of the 

 spiral arm and the dorsal region of a lateral arm. (From Richards (87).) 



are worked up into mucous pellets to be eaten or rejected. The gill filaments 

 are covered by mucus, which is secreted by an endostyle at their base. 

 Besides lateral cilia, the filaments bear frontal and abfrontal cilia which beat 

 towards their tips. Fine particles in the inhalant stream are caught on the 

 gill filaments, and are transported by frontal cilia across the ventral surface 

 of the gill to a food channel. This is a ciliated groove placed in the left 

 side of the mantle cavity and roofed above by the tips of the gill filaments. 

 In it the collected food particles, embedded in mucous strings, are carried 

 forwards towards the mouth where they are seized by the radula and 

 ingested. 



The method of filtering is essentially the same in other ciliary-feeding 

 prosobranchs. Mucus used for entangling food particles is secreted by a 



