A HISTOLOGICAL STUDY OF THE ZEISSL MEMBRANE FOUND IN THE DIGESTIVE TRACT OF THE DANUBE SALMON Hucho hucho (Linnaeus, 1758).

The digestive system of fish is different from one species to another, depending on the type of food ingested. Danube salmon Hucho hucho (Linnaeus, 1758) is a critically endangered species of the Salmonidae family with the threat of extinction looming large, therefore conservation efforts are urgently needed. This study presents a detailed microscopic analysis of the Zeissl membrane in Danube salmon, through histological means. The biological material analyzed consisted of six fish raised in a specialized breeding farm for restocking purposes. Samples were collected from the gastrointestinal tract and processed using histological paraffin embedding. The Zeissl membrane was present in all studied segments, but its structure and development varied. It comprised the stratum compactum (SC) and stratum granulosum (SG). The SC formed a continuous membrane with unequal thickness in most of the studied segments, except for the cardia area of the stomach, where it appeared discontinuously, and the duodenum, where it only appeared between the apertures of the pyloric caeca. Aside from its role in limiting gastrointestinal distension, it may have other implications for the morphophysiology of the Danube salmon digestive tract. [ABSTRACT FROM AUTHOR]