CHAO: DIGESTIVE SYSTEM OF CUNNER 



1961), the alimentary tract of the cunner con- 

 sists of neither a morphologically nor a physi- 

 ologically differentiated stomach. The alimen- 

 tary tract can be divided into several regions; 

 the preesophageal cavities, esophagus and 

 esoj)hageal-intestinal valve, intestine, rectal 

 valve and rectum, and associated organs. 



Preesophageal Cavities 



This region has three parts: the mouth, buccal 

 cavity, and pharyngeal cavity (Figure 2). 



MORPHOLOGY. — Gunners have large ca- 

 ninelike or incisorlike teeth on the premaxillary 

 and dentary bones. The protrusible premaxillary 

 bears three or four rows of conical teeth 

 directed posteriorly, as are the two or three 

 rows of dentary teeth. The most anterior rows 

 of both premaxillary and dentary teeth are 

 two to four times larger than the other rows. 

 Also, the anterior most teeth are larger than 

 the following ones on the same row. Teeth 

 from 15 specimens (130-230 mm SL) numbered 

 32-66 on the premaxillary and 21-44 on the 

 dentary. The number of teeth increases with 

 the size of the fish. Developing teeth were 

 found at the edges of the older teeth on all 

 tooth bearing bones. Longitudinal ridges of 

 mucous membrane extended from the vomer 

 to the pharynx on the roof of the buccal cavity. 



The buccal valve is located posterior to the 

 buccal cavity (Figure 2). There are no teeth 

 on the vomer and palatine bones. A large tongue 

 covers the entire floor of the anterior pharyn- 

 geal cavity and forms a sublingual cavity. The 

 pharyngeal cavity is bounded laterally by gill 

 arches. A yellowish brown mucous layer, patch- 

 like and thicker than that in the buccal cavity, 

 covers the entire roof and posterior part of the 

 floor. Strong mucous secreting activities occur 

 in this area. Both the upper and lower pharyn- 

 geal teeth are surrounded partially by this 

 mucus. The pharyngeal teeth (upper 41-59, 

 lower 28-56) are multitubercular and molari- 

 form. A pair of upper pharyngeal bones attach 

 to the epibranchial bones and a triangular 

 lower pharyngeal plate is attached to the basi- 

 branchial bones. 



HISTOLOGY.— The mouth is lined with a 

 stratified epithelium of the transitional type 

 without a cuticular surface. The mucosa is 

 thrown into ridges which start at the inner 

 side of the protrusible lips (Figure 3) and 

 extend to the esophagus. Taste buds lie on the 

 crest of the ridges, and basophilic mucous 

 secreting cells occur at the sides and bases, 

 but the large acidophilic mucous cells present 

 in the skin are absent here (Figure 3). Poly- 

 hedral cells and low-columnar cells constitute 

 the rest of the layer. The mucosal laver and 



Figure 2. — Mouth (M), buccal cavity 

 (B), and pharyngeal cavity (P) of a 

 40-mm SL juvenile cunner ( X 40: 

 power of observation). bv, buccal 

 valve; d, dentary teeth; p, premaxil- 

 lary teeth: T, taste bud. 





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