Intact teeth were obtained from three cadavers of known age 56, 67, and 76 years, respectively. Cross-sections 100-150 micrometers thick were taken from the roots using a diamond saw. Individual sections were stained, mounted on glass slides, and photographed on a light microscope. The usual number of years for the eruption of any particular tooth were added to the annulation count to determine the estimated age for that cadaver.

An anatomical study of the digestive tract of the channel catfish revealed that the oesophageal mucosa was longitudinally folded and that secondary folds were occasionally located on the primary longitudinal folds. The infoldings were more numerous near the stomach. The stratified squamous epithelium covering the folds was made up of a basal layer, large mucous cells and simple squamous cells on the surface. The epithelium on the side of the folds consisted primarily of mucous secreting cells. Taste buds were observed between mucous cells on the apical portion of the oesophageal folds and were more prevalent in the cranial part of the oesophagus. The remaining layers of the oesophagus were: a lamina propria-submucosa, tunica muscularis and adventitia or serosa.The J-shaped stomach had two regions: a large sac-shaped region containing gastric glands and a smaller, nonglandular pyloric region. The large rugae of the stomach became gradually smaller near the pylorus. There was a well developed pyloric sphincter. The mucosa included a simple columnar epithelium, a lamina propria and adventitia or serosa.The intestine could be differentiated into a thick ascending segment, a descending segment, a thin convoluted segment and a thicker terminal segment, the rectum. Many mucosal folds containing branched villi characterized the ascending segment of the intestine. The descending and convoluted segments contained fewer folds with shorter and lessbranching villi and were smaller in diameter and thinner walled. Descending and convoluted segments were also mildly convoluted and accounted for 80% of the total length of the intestine. An intestinal valve with a sphincter marked the beginning of the rectum. There was an approximately four-fold increase in the thickness of the tunica muscularis of the terminal segment of the intestine.

Abstract. Granulomatous hepatopancreatitis of unknown etiology has been considered an important disease of Texas shrimp mariculture since 1985. Samples of Pacific white shrimp (Penaeus vannamei) were collected during 1986, 1987, and 1990 from three farms and an experimental mariculture facility with histories of production loss and increased mortality rates. Histologic and ultrastructural examination of shrimp from the four sites demonstrated two morphologically distinct, Gram-negative, double-enveloped, intracytoplasmic bacteria in necrotic hepatopancreatic epithelium. The more numerous small, pleomorphic rod as well as the helical organism are both taxonomically unclassifiable. The helical organism lacked ultrastructural characteristics of previously described helical or spiral bacteria. The relationship between the two organisms is unknown, but the pleomorphic rod is thought to play a major role in the disease. The role of a bacterial agent(s) in subsequent disease episodes is suggested by the observation that the use of oxytetracycline-medicated feed resulted in increased production and survival. Hepatopancreatic tubular epithelial necrosis and shrimp mortality correlated directly with the extent of infection by the small pleomorphic rod. Individual discrete bacteria were identified microscopically by Steiner and Steiner's method. Three major developmental stages of the disease were characterized based on the extent and number of hepatopancreatic tubular epithelial cells containing bacteria, the degree of tubular interstitial inflammation, and the extent and chronicity of tubular necrosis. Additional studies are needed to clarify the roles of the different bacteria identified and the potential role of environmental factors on the disease process.

Fourteen specimens of the hepatopancreas of the Pacific white shrimp, Penaeus vannamei, were prepared for examination with the transmission and scanning electron microscopes and with the light microscope. The histology and ultrastructure of this organ is similar to that seen in other Decapoda. At the ultrastructural level, it was observed that B-cells rupture at approximately the level of gap junctions located on the lateral plasma membranes of the cells, and discharge the contents of their large vacuoles into the intercellular space. This efflux of enzymatic material may be the mechanism by which cells are released from the wall of the tubule at the proximal end: the rupture and collapse of a B-cell may be analagous to the removal of the keystone which supports an arch. Deprived of support, and lacking structural adaptations for cohesion (there are no desmosomes or interdigitations in the epithelium) and with the intercellular material digested, the remaining intact cells collapse into the lumen of the tubule. The lysis of individual cells of all types - R-, F-, and B-cells - may contribute to the tubules’ total complement of digestive enzymes.

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