Morphological study of the gastrointestinal tract of Larimichthys crocea (Acanthopterygii: Perciformes)

Abstract

The present study aimed to investigate the macroscopic and histological structure of the gastrointestinal tract (GIT) of Larimichthyscrocea (Richardson, 1846). It consists of esophagus, stomach regions, pyloric caeca, intestinal regions, and rectum. Sixteen tubular light yellowish pyloric caeca of similar sizes were observed in all individuals. The digestive wall consists of mucosa, submucosa, muscularis, and adventitia. No major differences appeared in the structure of the tunica, epithelial cell types, connective tissues and musculature glands of L.crocea GIT. The mucosal epithelia in the oesophagus has longitudinal branched folds with frontward and hindmost zones. The gastric tunica mucosa has a characteristic folded structure and can be divided into three regions. The intestinal tunica mucosa is characterized by villi structures and numerous mucus-secreting cells. Mucus-secreting goblet cells were strongly positive to AB at pH 2.5 in the oesophagus (excluding gastro-oesophageal junction) and intestine mucosal regions, which indicates an abundance of carboxylate mucins. The surface epithelia of the gastric mucosa is PAS-positive and AB-negative. SEM examination revealed that cells in the epithelium of the esophagus have an unbroken apical layer and goblet cells. The intestinal coefficient (IC) of L.crocea was 0.80 ± 0.21, consistent with a carnivorous or omnivorous habit. Our study adds the knowledge of the digestive system of L.crocea and might be useful in the management of L.crocea stocks.

Description of the unusual digestive tract ofPlatax orbicularisand the potential impact ofTenacibaculum maritimuminfection

“…In spite of the convolutions observed, the RIL or IC is relatively low (1.47 ± 0.14), compared to other species (from 0.5 to 13.0 depending on the species) and is in the range of carnivorous species ( Ray & Ringø, 2014 ; Kalhoro et al, 2019 ). The RIL or IC is used as a morphometric marker to classify fish according to their feeding habits, age or development ( Kalhoro et al, 2018 ; Kalhoro et al, 2019 ). However, the link between intestinal morphology (e.g., length) and fish diet due to specific requirements for the digestion is still controversial ( Kapoor, Smit & Verighina, 1976 ; Wilson & Castro, 2010 ; Dala-Corte, Becker & Melo, 2017 ; Kalhoro et al, 2018 ; Kalhoro et al, 2019 ).…”

“…The RIL or IC is used as a morphometric marker to classify fish according to their feeding habits, age or development ( Kalhoro et al, 2018 ; Kalhoro et al, 2019 ). However, the link between intestinal morphology (e.g., length) and fish diet due to specific requirements for the digestion is still controversial ( Kapoor, Smit & Verighina, 1976 ; Wilson & Castro, 2010 ; Dala-Corte, Becker & Melo, 2017 ; Kalhoro et al, 2018 ; Kalhoro et al, 2019 ). Indeed, several studies about intestine plasticity highlighted the drastic changes in GIT length especially following starvation ( Kapoor, Smit & Verighina, 1976 ; Zaldúa & Naya, 2014 ; Ramírez, Davenport & Mojica, 2015 ).…”

“…The transition between the esophagus and the stomach even if not well defined, can be identified using the color of the organ, muscle layers and the presence or absence of mucous subepithelial glands ( Hellberg & Bjerkas, 2000 ; Ray & Ringø, 2014 ; Vidal et al, 2020 ). The stomach displays a siphonal (J or U) shape which is the most common type among fish (e.g., Eastman & DeVries, 1997 ; Løkka et al, 2013 ; Kalhoro et al, 2018 ). P. orbicularis has pyloric caeca as approximately 60% of teleosts (e.g., Pedersen & Falk-Petersen, 1992 ; Løkka et al, 2013 ; Aguilar-Medrano, Kobelkowsky & Balart, 2015 ; Alix et al, 2017 ; Kalhoro et al, 2018 ; Kalhoro et al, 2019 ; Vidal et al, 2020 ; Verdile et al, 2020 ).…”

“…The stomach displays a siphonal (J or U) shape which is the most common type among fish (e.g., Eastman & DeVries, 1997 ; Løkka et al, 2013 ; Kalhoro et al, 2018 ). P. orbicularis has pyloric caeca as approximately 60% of teleosts (e.g., Pedersen & Falk-Petersen, 1992 ; Løkka et al, 2013 ; Aguilar-Medrano, Kobelkowsky & Balart, 2015 ; Alix et al, 2017 ; Kalhoro et al, 2018 ; Kalhoro et al, 2019 ; Vidal et al, 2020 ; Verdile et al, 2020 ). These blind-ended ducts are probably involved in the surface area increase for absorption and digestion ( Pedersen & Falk-Petersen, 1992 ; Ray & Ringø, 2014 ).…”

Development of the digestive system of Argentine hake, Merluccius hubbsi, larvae

“…To protect against physical and chemical abrasions, the digestive tract is covered by at least one mucus layer that contains mainly glycoconjugates (GCs; Kim & Ho, 2010). Each type of GCs has a specific functional role (Carlucci et al, 2019; Cohen et al, 2016; Kalhoro et al, 2018; Wang et al, 2017). Acidic mucins fulfill functions related to increased viscosity (Díaz, García, & Goldemberg, 2008), lubrication and protection of the epithelium from mechanical damage and against pathogens (Cohen et al, 2016; Sarasquete, Gisbert, Ribeiro, Vieira, & Dinis, 2001).…”