Histostructural ontogeny of esophagus in common bream (Abramis brama) during early developmental study using light microscopy and transmission electron microscope (TEM)

Abstract

This study aimed to investigate the histoarchitecture of the esophagus in common bream (Abramis brama) during early development using light microscopy and transmission electron microscope (TEM) from hatching up to day 60 post hatch (DPH). Larvae were sampled randomly every day from hatching time to 6 DPH, on every alternate day from 8 DPH to 20 DPH, every 5 days from 25 DPH to 40 DPH, and two last samples have down at 50 and 60 DPH. Then fish larvae were fixed by immersion in Bouin´s solution and 4% glutaraldehide (pH = 7.4). Results showed that the esophagus differentiated from the anterior part of the alimentary tract at hatching time. At 1 DPH, the esophagus lined by squamous cells and forming a tine tubular structure lined with cubical cells. First goblet cell was observed at 2 DPH in the mucosal layer of the esophagus. At 3 DPH, they showed presence of the various mucosal material. In addition, epithelium of the esophagus changed to columnar cells. The first taste bud was detected at 5 DPH and the main phenomenon was the appearance of a serrated outline of the esophagus apical cells. Longitudinal folds of the esophagus were developed at 8 DPH. No remarkable histological changes were observed till 25 DPH, but the number of the taste buds and goblet cells and their size were increased. From 25 to 60 DPH, low dense of goblet cell, increasing in posterior esophagus region, led to differed histological characteristics with anterior esophagus segment encompassed increasing number of taste buds.

Keywords

• esophagus ontogeny
• common bream
• abramis brama