CHAO: DIGESTIVE SYSTEM OF GUNNER 



in the intestinal wall: mucosa, submucosa. 

 muscularis, and serosa (Figure 11). 



MUCOSA. — The epithelium of the mucosa 

 consists mainly of columnar absorptive cells 

 and goblet cells. The columnar absorptive cells 

 of the cunner are similar to those of the 

 stomachless cyprinids described by Al-Hus- 

 saini (1949a). The epithelium can be divided 

 into the same four regions: the free border, the 

 subborder, the supranuclear, and the infra- 

 nuclear zones (Figures 12, 13, 14). The free 



border of the mucosa is sharply defined 

 throughout the intestine. The striated border 

 (or subborder) in the active digestive epithelium 

 (Figure 14) is slightly thicker than in the 

 inactive (Figure 13) epithelium. It stains in- 

 tensively with periodic acid-Schiff (PAS) (Figure 

 15) and shows very prominent digestive effects 

 in the active epithelium (Figure 14). In the 

 resting cell of starved fish, the cytoplasm can 

 be divided into a subcuticular zone and a layer 

 of fine granules (Figures 12. 13). The sub- 

 cuticular zone in starved fish is a compara- 



FiGURE 11. — Mucosal folds of the 

 posterior section I of the intestine 

 of a :40-mm SL cunner (X 100, 

 X.S.). cm, circular muscle layer: Im, 

 longitudinal muscle layer: mc, mu- 

 cosa; ms, muscularis: Sm, submucosa; 

 sr, serosa. 



mc 











-1 R ^; • h** - i 



^■^■-"' * ■:„/:,.. 



J 0. .4 



1^ 



Jt. f 



gi 



\ 



-sp 



Figure 12. — Free border (f) of the 

 columnar epithelium of the intestine 

 (I) of cunner (X 1,000). gl. granular 

 layer: go. goblet cell: r, rodlet cell: 

 sb, subborder: sc. subcuticular zone: 

 sp. supranuclear zone. 



573 



