Histopathological Alteration of the Internal Organs in the Fingerlings Carp Fed with Variable Proportion of Blue Algae

Microphytes are considered as eco-friendly and alternative for antibiotic, making them a highly important, valuable substitute and recommended in aquaculture. Spirulina spp. is one of microphytes that is introduced recently to the fish diet as a source of protein. Therefore, the study aimed to evaluate the histopathological effects of spirulina added to fish diet at variable levels (0, 1.45, 2.9, 3.54 and 6.1%) over a 56- day feeding trail. The samples of  liver, intestine and kidney were collected for histological technique after the experimental period. Microscopic examination revealed morphological alteration in the apex of the villi in intestine with sloughing in fish diet with spirulina at 1.45%. Other histopathological changes varied in severity according to the supplemented spirulina percentage. These include cellular infiltration, cell growth disturbances, villi adhesion with narrowing villi crypt and necrosis. In the liver, lesions were severe in the fish treated with 6.1% of spirulina which is characterized by circulatory disturbances as thrombus formation in the central vein and dilatation of sinusoid with infiltration of inflammatory cell, fibrosis, and vacuolar degeneration. The end product metabolism of high protein component in  spirulina lead to kidney architecture disturbances in all fish treatment. It is histologically characterized by dilatation in the Bowman’s space with edema and hyperaplasia of the epithelial cells lining renal tubule, necrosis in some tubule with edema and interstitial nephritis. Although microalgae as spirulina is beneficial and widely used in fish aquaculture, however this study highlight potential adverse effects and  tissue  disorder, particularly at high percentages. Future study is recommended to study the histopathilogical effects of spirulina to better understand optimal dosage in fish diets.