Date of Award

Spring 1966

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Committee Chair

J.F. Walker

Committee Chair Department

Biological Sciences

Committee Member 3

William Cliburn

Committee Member 3 Department

Biological Sciences

Abstract

This experimental work describes the histology and morphology of the stomach of the white shrimp. Various routes and passageways for the movement of food and feces from the esophagus through the cardiac and pyloric fore-gut, the mid-gut, and the hind-gut to the anus are described.

The mandibles of Penaeus fluviatilis have both incisor and molar surfaces which partially masticate food entering the fore-gut. Fine particles of food percolate in to two pairs of highly setose longitudinal ventral grooves of the cardiac stomach which lead into the anterior pyloric stomach. Before entering the pyloric stomach, large bits of food are reduces in size by the action of the gastric mill situated in the postero-dorsal cardiac roof and walls. This mechanical apparatus, the gastric mill, consists of 12 ossicles or sclerites which are closely associated with one another. Muscle contractions cause simultaneous movement of a single median tooth and two lateral teeth, the median tooth moving forward in a swinging, gliding motion and the lateral teeth moving closer together. The contact of these three teeth reduces the size of large particles before entering the pyloric stomach.

Each of four valves between the cardiac and pyloric stomachs selects maximum sized particles and directs them to various chambers of the pyloric stomach. Here they are acted upon by other filtering devices or are shunted away as undigestible material by various setose grooves toward the posterior pyloric opening.

Only very fine particles enter the main filtering device, the pyloric ampullae. The digested particles pass into the diverticula of the hepatopancreas for absorption into the blood stream. The undigestible materials enter the mid-gut from the pyloric stomach by way of the dorsal pyloric valve.

The entire fore-gut with the exception of the lateral valves is lined with cuticle from 25 to 50 microns in thickness. Outside the cuticle is a single layer of epithelium from low cuboidal to tall columnar cells. Outside the epithelium is loose connective tissue in which are embedded circular longitudinal and constrictor muscles.

Download

Share

COinS