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Email the author (Login required) Histological and histochemical study of Rhamdia quelen digestive tract organogenesis under intensive larviculture conditions
DOI: https://doi.org/10.3856/vol42-issue5-fulltext-17
Abstract
The development and the chronological differentiation of the digestive tract in Rhamdia quelen larvae were histologically studied from hatching up to 20 days post-hatch (dph) with 530 accumulated thermal units (ATU). Larvae were kept under intensive larviculture conditions and fed with Artemia nauplii. The anatomical and histological differentiation of the digestive tract was an asynchronous process with an undifferentiated straight tube at 1 dph (4.87 mm). Whereas, at the onset of feeding it was organized into four different histological regions: oropharyngeal cavity, oesophagus, incipient stomach and intestine. At 15 dph (397.5 ATU), the organization was similar to that found in adults. At hatching, taste buds were observed in barbels and oropharyngeal cavity, distributed among a stratified epithelium with mucous cells. A stratified epithelium with mucous cells secreting neutral and acid mucopolysaccharides was observed in the esophagus at the onset of feeding. In the stomach, gastric glands became visible between 8-10 dph (212 a 265 ATU), being entirely active at 20 dph. On the first day of life, the intestine showed a simple columnar epithelium without evident characteristics of absorptive activity, whereas 4 dph (106 ATU) microvilli on the apical region and a significant accumulation of intracytoplasmic lipid and protein in the anterior and posterior intestine were observed, respectively. In the intestine, the mucous cells were acid and neutral, being both types of cells most abundant in the distal region. Histological results indicate that R. quelen larvae are able to efficiently digest and absorb food from the first days of life.
