Cell and Tissue Journal

Abstract Aim: The use of algae as a food additive has many positive effects such as increasing the quality, health, and greed of food and increasing the level of growth and immunity in aquatic animals. Among the algae with many uses are the members of the red algae branch, which are seen in red due to the large amounts of phycoerythrin and phycocyanin pigments. These algae belong to primary multicellular plants of the marine species, non-flowering without roots, stems, and leaves, and they reproduce sexually. The current research was conducted to replace red algae in the diet in stomach, liver histomorphology, and some growth factors of Nile tilapia, one of the most important commercial species in the world.
Material and Methods: For this purpose, after 8 weeks of preparation, fish were fed diets containing zero, 3%, 6%, and 9% of food weight with red algae with three repetitions in each treatment. After the end of the rearing period, the fishes were anesthetized and after opening the abdominal area while measuring some growth factors, a 0.5 cm tissue sample was taken from the middle part of the stomach and liver and placed in a 10% formalin buffer solution. After going through the routine steps of tissue preparation, including dehydration with alcohol, clarification with xylol, blocking with paraffin, cutting with a thickness of 4-6 microns, and staining, finally, the study was done with a light microscope. SPSS software version 21 was used for statistical analysis of data.
Results: Microscopic and anatomical studies of the stomach and some growth factors of the digestive system showed an increase in the measured factors as percentage of weight gain, especially in the group receiving the diet containing 9% red algae. The results of microscopic studies on the stomach showed that the mucosal lining of the stomach is of a simple type with nuclei near the base. This tissue is stretched from the surface of the mucous membrane to the inner part, so that at the beginning of the stomach, short but deep folds were also observed at different intervals. In the lamina propria of gastric mucosa, simple tubular glands were observed, whose tissue consists of a row of short cubic to cylindrical cells, which have spherical to elongated nuclei and basophils attached to the base of the cells. These cells had strong acidophilic color and covered all the lamina propria. Also liver was completely lobulated and the pancreas was located in the form of an appendix gland inside.
Conclusion: The results of this research showed that in terms of the structural characteristics of the stomach and liver tissue such as mucous glands, epithelium thickness, thickness, mucus height, and anatomical growth of the digestive system, red seaweed powder can be a suitable substitute for fish meal in the diet. Tilapia, along with possible substitutes in other animal and vegetable proteins, can be used to feed this fish, which will eventually reduce the cost and reduce the dependence on fish powder to supply the protein needed by Nile tilapia.