The digestive tract of the amberjack Seriola dumerili, Risso: a light and scanning electron microscope study

Abstract

The histology of the digestive tract of the amberjack (Seriolu dumerili, Risso) was studied using light and scanning electron microscopy. The anterior oesophagus mucosa displays primary and secondary folds lined with a stratified squamous epithelium with fingerprint-like microridges which is substituted, on the top of theoesogaster folds, by a simple columnar epithelium with short microvilli. Only primary folds are present in the stomach. The anterior portion is rich in simple tubular glands, whereas the oesogaster and the pyloric region are devoid of them. Pyloric caeca and anterior and middle intestine mucosa display the same pattern of folding. The dominant cell type is the enterocyte, which exhibits larger and thinner microvilli in the caeca than in the intestine. The columnar epithelium of the rectum is replaced, in the anal sphincter, by a stratified flattened epithelium. Goblet cells are numerous throughout the whole length of the tract with the exception of the initial part of the oesophagus, the oesogaster, the stomach and the anal sphincter. Mucosubstances have been shown to vary in the different regions of the gut: acid mucines are found in the oesophagus, pyloric stomach, caeca, intestine and rectum, whereas neutral mucosubstances dominate in the anterior portion of the stomach. The muscularis is well developed throughout the length of the tract: two layers of striated muscle at the oesophageal level; two layers of smooth muscle in the stomach wall and three at the intestinal level.

Scanning Electron Microscopy of the Gastrointestinal Tract of Nile Perch (Lates niloticus, Linneaus, 1758)

“…The mucus serves to reduce friction in the path of entry of the prey making swallowing possible. The fingerprint-like micro ridges observed on the surface cells in the oral cavity and oesophagus in Nile perch are similar to those reported in Solea senegalensis (Arellano et al, 2001), in Dentex dentex (Carrassón & Matallanas), in Seriola dumerilli (Grau et al, 1992), in Rita rita (Yashpal et al), and in several other seawater and freshwater fishes (Meister et al, 1983). These ridges have been thought to play an important role of protecting the buccal-oesphageal surface from trauma and providing an anchor to the mucus secreted from the goblet cells (Wilson & Castro, 2010).…”

Comparative study on the intestine of Schilbe mystus and Labeo niloticus in correlation with their feeding habits

“…This finding agrees with that of Gargiulo et al (1998), in Tilapia spp., and Albrecht et al (2001), in Leporinus friderici and Leporinus taeniofasciatus. However, this result contradicts with that of Grau et al (1992) who described three layers of unstriated muscle fibres throughout the whole intestinal length of Seriola dumerili.…”

“…This result agrees with that of Grau et al (1992) in Seriola dumerili, but contradicts with that of Gargiulo et al (1998) who stated that the thickness of the rectal muscularis of Tilapia spp. is the same as the rest of the intestine.…”

“…numerous mucosal goblet cells were also found by Martin and Blaber (1984), in three carnivorous Ambassis species, and Grau et al (1992), in the carnivorous Seriola dumerili. The farmer authors added that the mucus may serve as a lubrication aid to defecation.…”

Effect of the herbal preparation Nozevit on the mid-gut structure of honeybees (Apis mellifera) infected with Nosema sp. spores

“…The secreted mucous layer functions to lubricate undigested materials and plays an important role in osmoregulation (Vegetti et al, 1999), the transfer of proteins or their fragments as well as of ions and fluids (Domeneghini et al, 1998) and protection from mechanical injuries or bacterial invasions. Mucosubstances secreted by the ventriculus (mid-gut) epithelium have been implicated in the absorption of easily digested molecules (Grau et al, 1992) and have a very important role in the intestinal absorption process, especially after starvation when the number of intestinal goblet cells increases (Kakamand et al, 2008). Also, as reported by Tibbetts (1997) mucous cells containing sialo-and sulfoglycoproteins promote an increase in the viscosity of secretion, which is likely to be play a protective role.…”