Summary
The histology and carbohydrate histochemistry of eight teleostean stomachs are compared. Three gross anatomical types of stomachs are described and their shapes appear to correlate somewhat with feeding habits. Each type can be divided histologically into a corpus and pylorus. Gastric glands, containing only one cell type, occur in the copora of all species, but are present in the pylori of esocids only. As a single cell can produce both enzymes and hydrochloric acid such cells may be comparable to those of amphibians but not mammals. Lamina propria and submucosa are indistinctly separated in corpora but better defined in pylori by an intervening muscularis mucosa. The arrangement of the muscularis into inner circular and outer longitudinal layers is the opposite of that seen in the esophagus. Gastric mucous cells show species variations in localization of epithelial mucosubstances, which in broad terms are recognized as sulfomucins, sialomucins and neutral mucosubstances. A piscivorous diet does not appear to demand any particular type of carbohydrate. Within the Centrarchidae, gastric pit cells vary in carbohydrate content from only neutral mucosubstance to only weakly acidic sulfomucin; two species contain both types. A positive PAS reaction on the surface of gastric epithelial cells is suggestive of a striated border and thus possibly absorptive function. The absence of stomachs in some teleosts and the evolutionary and dietary significances are discussed.
Methodology
The following species were studied: Family Centrarchidae: Ambloplites rupestris (rock bass), Lepomis nacrochirus (bluegill sunfish), Micropterus salmoides (largemouth bass), Pomoxis nigromaculatus (black crappie) ; Family Cyprinidae: Notemigonus crysoleucas (golden shiner), Pimephales promelas (fat- head minnow); Family Esocidae: Esor americanus (grass pickerel), E. lucius (northern pike) ; Family Ictaluridae: Zctalurus nebulosus (brown bullhead) ; Family Percidae: Perca flavescens (yellow perch). Adult fish were obtained mainly from Lake Opinicon, Ontario, the exception being specimens of P. promelas and E. americanus, which were obtained from Jones Creek near Mallory- town, Ontario. Pieces of stomach were fixed in either Bouin's fluid or 10% neutral buffered formalin. They were embedded and sectioned at 6 pm. Representative sections were stained with hematoxylin and eosin, phosphotungstic acid hematoxylin and the Fontanna-Masson Silver method. Neutral mucosubstances were identified by employing the periodic acid- Schiff (PAS) method, both with and without previous saponification with 0.5% KOH in 70% ethanol for 30 minutes (Culling et al., 1971).