Comparative Nutritional and Histological Analysis of Malabar Red Snapper (Lutjanus malabaricus) and Asian Seabass (Lates calcarifer)

Abstract

This study offers a comprehensive morpho-histological analysis of the gastrointestinal tract (GIT) of the Malabar red snapper. A comparison of its GIT morphology with that of the Asian seabass reveals similarities and differences between the two species. Additionally, the moisture content, crude protein, and ash in the fillets of Malabar red snapper and Asian seabass were slightly different, with Malabar red snapper exhibiting higher levels of essential fatty acids. Furthermore, higher levels of the polyunsaturated fatty acid (PUFA)/saturated fatty acid (SFA) ratio and docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio, and a lower omega-6/omega-3 ratio, were observed in Malabar red snapper compared to Asian seabass. The Malabar red snapper's esophagus featured protective mechanisms such as simple columnar epithelial cells, mucous-secreting glands, and goblet cells that were predominantly stained for acid and neutral mucosubstances. Furthermore, its stomach, with mucus cells that were weakly stained for acid mucosubstances, exhibited distinct regions with varying glandular densities, with the pyloric region featuring few glands. The pyloric caeca of the fish were composed of five finger-like structures and few goblet cells. Several goblet cells gradually increased from the anterior to the posterior region of the intestine. These findings provide useful insights for the aquaculture sector, focusing on Malabar red snapper.

Keywords: Malabar red snapper; fillet fatty acids; gastrointestinal micromorphology; goblet cells.

Figure 1

Section of Malabar red snapper fillet that was collected for fatty acid, moisture, protein, and ash analysis. (A) Fish, (B) fillet.

Figure 2

Morphology of the red snapper gut. (A) Esophagus, (B) cardiac stomach, (C) fundic stomach, (D) pyloric stomach, (E) pyloric caeca, (F) anterior intestine, (G) mid intestine, (H) posterior intestine, and (I) rectum.

Figure 3

Transverse sections of red snapper esophagus. The tissues were stained with Hematoxylin and Eosin (H&E) ((A): 10×, (B): 40×, (C): 100×), and subsequently stained with Alcian Blue-Periodic acid-Schiff (AB-PAS) ((D): 100×). Abbreviations: Esophageal glands (EG), goblet cells (GC), lamina propria (LP), lumen (LU), mucosa (MU), sub-mucosa (SM).

Figure 4

Transverse sections of red snapper stomach. Cardiac stomach ((A): 10×, (D): 40×), fundic stomach ((B): 10× and (E): 40×), and pyloric stomach ((C): 10× and (F): 40×). The sections are stained with H&E. Cardiac stomach ((G): 100×), fundic stomach ((H): 100×), and pyloric stomach ((I): 100×) stained with AB- PAS. Abbreviations: cardiac gland (CG), fundic gland (FG), gastric pits (GP), lumen (LU), mucosa (MU), submucosa (SM), mucosal cells (MC), gland cells (GLC).

Figure 5

Transverse sections of red snapper pyloric caeca. The sections are stained with H&E ((A): 10× and (B): 100×) and PAS-AB ((C): 100×). Abbreviations: goblet cells (GC), mucosa (MU), muscularis (MS), submucosa (SM).

Figure 6

Transverse sections of red snapper anterior intestine. The sections are stained with H&E ((A): 10×, (D): 100×) and AB-PAS ((G): 100×), mid intestine H&E ((B): 10× and (E): 100×) and PAS-AB ((H): 100×), and posterior intestine H&E ((C): 10× and (F): 100×) and PAS-AB ((I): 100×). Abbreviations: goblet cells (GC), lumen (LU), muscularis propria (MS), serosa (SE), submucosa (SM), Vili (VI).

Figure 7

Transverse sections of the red snapper rectum. The sections are stained with H&E ((A): 10×, (B): 100×) and PAS-AB, ((C): 100×). Abbreviations: goblet cells (GC), mucosa (MU), muscularis propria (MS), serosa (SE), and submucosa (SM).