Unique localization of disseminated pancreas in the oesophagus of catfish (clarias gariepinus) with reference to sexual dimorphism.

BACKGROUND: The fish pancreas has been reported to be composed of two portions: compact and disseminated. However, little has been elucidated in catfish. The present study describes a unique localization of the disseminated pancreas in African catfish. METHODS: The sections were obtained and used for either routine histological examination following staining with haematoxylin and eosin (H & E), periodic acid-Schiff's, or were subjected to immunohistochemical staining for detection of both insulin-producing ß cells and glucagon-producing alpha cells. RESULTS: Our investigation showed that the pancreas of catfish consisted of both compact and disseminated portions. The compact pancreas was embedded in the mesenteric adipose tissue between the spleen, stomach and liver. However, the disseminated one showed unique localization in the tunica adventitia of the middle portion of the oesophagus. The pancreas consisted of two portions, exocrine and endocrine. Furthermore, in both types of pancreas, the female showed a significantly higher ratio for the endocrine islet area/pancreatic tissue area than that of the male and also a significantly higher ratio for both insulin- and glucagon-positive area/islet area in the female pancreas (compact and disseminated) than that of the male. IN CONCLUSION: The present study provides evidence on a unique localization of the disseminated pancreas in the oesophagus of catfish. Furthermore, we revealed sex-related difference in the endocrine portion in both pancreatic tissues with more development in the female. The study suggests that sex hormones could be contributed to such sexual dimorphism. However, further investigation is required to compare the degree of development during the spawning and resting seasons.