Ultrastructure of Brachycoelium salamandrae Gastrodermis with Observations on the Effects of Starvation

Abstract

The fine structure of the digestive tract of the digenetic trematode Brachycoelium salamandrae was studied. The digestive tract consisted of a foregut region whose lining was cytoarchitecturally similar to the general body tegument. Glands opened into the lumen of the foregut via microtubular-supported ducts. The junction between the foregut and the cellular gastrodermis was marked by a prominent desmosome. The apical plasma membranes of the gastrodermal cells were amplified by means of lamellae. The cells display an extensive rough endoplasmic reticulum, mitochondria, and numerous Golgi complexes. Two types of vesicles were observed. One type was a vesicle with a homogeneous matrix that appeared to be associated with the emitting face of Golgi complexes. Another structure was the multivesicular body that displayed acid phosphatase activity. This latter organelle was observed at times to be associated with autophagic vacuoles and is believed to be a part of the lysosome system of the gastrodermis. Starvation of the worms resulted in an increase in the disintegration of gastrodermal cells as well as an increase in the number of autophagic vacuoles in the cytoplasm. Ultrastructural organization of the adult diges- tive tract representative of nine families and 22 species of digenetic trematodes has been described to date (Fujino and Ishii, 1979). A number of cytochemical studies have supplemented the morphological studies and have provided invaluable information pertaining to the func- tion of portions of the digestive tracts of these organisms (see Erasmus, 1977, for a review). The objective of the present investigation was to study the ultrastructure of the digestive tract of Brachycoelium salamandrae, a trematode family whose ultrastructure has hitherto not been described. Preliminary cytochemical studies were made in order to compare distribution of acid phosphatase activity in both normal and starved worms. This aspect of the study was designed to provide greater understanding of the function of certain organelles associated with the digestive tract as well as provide a base for comparison of the distribution of the enzyme in B. salamandrae with that found in other digenea.