Ontogeny of the digestive tract in mud loachMisgurnus anguillicaudatuslarvae

Abstract

This study on histological and mucous histochemistry characteristics of the digestive system of loach (Misgurnus anguillicaudatus) was carried out from hatching (0 day after hatching, DAH) until 45 DAH. The peculiar development of both digestion processes and air-breathing functions of the intestine was revealed. At 3 DAH, both the mouth and anus opened along with the first feed. At 4 DAH, lipid vacuoles appeared in the anterior part of the intestine and at 5 DAH the acidophilic supranuclear vacuoles appeared in the posterior part of the intestine. Mucous cells occurred in the buccopharynx and oesophagus after mouth opening and grew both in number and size as larvae grew. At 15 DAH, blood capillaries were found in the posterior part of the intestine. At 20 DAH, as a valve appeared in the intestine, the whole intestine could be divided into anterior, mid and posterior parts. With large numbers of blood capillaries and a very thin wall, a gas-blood barrier formed in the posterior intestine, which indicated that the dual roles of intestine were formed. These results suggested that the air-breathing function of the digestive tract formed from 15 to 20 DAH, which is a critical period for loach larvae.

Histological structure of the digestive tract and digestive enzymatic activity of juvenile Pacific seahorse (Hippocampus ingens)

“…The posterior esophagus has a greater muscle layer. This arrangement in the esophagus implies that the anterior esophagus functions as a food lubricant due to the presence of goblet cells and also as the first barrier against bacteria due to the immune function reported of the mucus secreted by these cells (Nazlić et al 2014, Cardoso et al 2015 while the posterior esophagus functions as a food transporter to the intestine with the large muscular area present covering the functions of an esophageal sphincter (Mai et al 2005, Zhang et al 2016. Three intestinal regions were distinguished in H. ingens; anterior, middle, and posterior.…”

“…In H. ingens, the proteolytic activity relies mainly on alkaline proteases due to the lack of a stomach and the acid proteolysis by the presence of HCl and pepsin. Additionally, intestinal pinocytosis of polypeptides in the posterior intestine followed by intracellular digestion has been reported as a mechanism in different species to compensate for the absence of a stomach (Govoni et al 1986, Ng et al 2005, Zhang et al 2016). In the case of H. ingens, the lack of pinocytotic vesicles in the posterior intestine may be due to the starvation condition of the studied individuals, which were not fed for at least 24 h before this study.…”

Molecular characterization of three muscle alpha actin genes in mud loach (Misgurnus mizolepis; Cypriniformes)

“…This modulation pattern could be explained by the need for the preparation of smooth muscles with the developments and differentiations of vascular and gastrointestinal organs. Although we did not examine histological ontogenesis of internal organs, initial developments of various smooth muscle-related organs including intestine might occur in that period, as scrutinized in a closely related Misgurnus species (M. anguillicaudatus) (Han et al 2013;Zhang et al 2016). Subsequently, ACTA2 transcripts were detected in a decreased level (i.e., at 5 DPH and afterwards).…”

Ontogenetic development of digestive tract and digestive enzymatic activities inSqualiobarbus curriculuslarvae

“…As the yolk sac was gradually absorbed, the gut lumen widened. The intestine region was divided into anterior, middle and posterior intestine with the development of the larvae, with the depth and number of the mucosal folds reducing from the anterior to the posterior intestine (Zhang et al, 2016). The intestine was in a folded state on 10 DPH.…”