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

Abstract

The Argentine hake Merluccius hubbsi is an important fishery resource of the Southwestern Atlantic Ocean and it is also a potential species for cultivation. In this work,the digestive system development in field-caught hake larvae was studied using histological and histochemical approaches. The digestive tract of larvae was divided into: oropharyngeal cavity (OPC), esophagus, stomach (that develops in the preflexion stage), and intestine. The annexed digestive glands consisted of the liver and the exocrine pancreas. At the beginning of the preflexion stage, teeth were developed in the OPC. There were mucous cells in the esophagus secreting different glycoconjugates from hatching. The enterocytes in the posterior intestine exhibited supranuclear vesicles associated with protein absorption. Mucous cells were observed in the posterior intestine in the preflexion stage and, in the anterior region, ending the flexion stage. Each type of glycoconjugates has a specific role. Acidic mucins lubricate and protect from mechanical damage, sialomucines protect from bacterial infections and neutral mucins regulate the acidity of mucus secretion, protect against abrasion and participate in the formation of the chyme, indicating a pregastric digestion. The liver was present since hatching with pancreatic tissue inside and increased in size acquiring the typical structure with hepatocyte cords, sinusoids, vacuoles, and hepatic duct. The hepatocytes vacuolization increased with larval development. The pancreas became extra-hepatic, with basophilic acinar cells and acidophilic zymogen granules. Throughout the ontogeny, the increased structural and functional complexity of the digestive system reflected the transition to exogenous feeding and nutritional increasing needs. K E Y W O R D S histochemistry, histology, ontogeny

The development of the digestive system and the fate of the yolk syncytial layer in postembryogenesis of Stenodus leucichthys nelma (Teleostei)

“…The intestinal MCs usually contain a mixture of neutral and acid glycoproteins (AB pH 2.5, 1.0 positive). The mucosubstances produced by the postvalvular intestine probably serve to lubricate the feces, and in other intestinal regions they are involved in the absorption of nutrients, protection of the digestive mucosa and immune defense (Cohen et al, 2020; Gisbert et al, 2014; Lazo et al, 2011; Marchetti et al, 2006; Ofelio et al, 2019; Zambonino‐Infante et al, 2008).…”

Morphological and biochemical approaches to assess the nutritional condition of the Argentine hake Merluccius hubbsi larvae from two different nursery areas

“…(2018) have analysed the nutritional status of M. hubbsi juveniles from the Patagonian stock within different areas of their main nursery ground, by a combination of different indexes (relative condition factor, hepato‐somatic index, lipid content and fatty acid composition in liver and muscle) combined with physical and biological information, and have found significant differences in the nutritional condition according to the predominant prey in the area. On the contrary, in M. hubbsi larvae, the histology and histochemistry of the digestive system have also been analysed, and no differences have been observed between both stocks (Cohen, 2019; Cohen et al ., 2020).…”