Liver and gill histopathological assessment of the nile tilapia (Oreochromis niloticus l.) exposed to polluted river water in Pampanga River, Pampanga

Abstract

Rivers hold around 0.49% of the planet’s freshwater system, however, through time humans continually pollute them. Currently, only 31.9% of the rivers of the world are assessed and from that, 54.7% are already impaired. The study at hand provided information regarding the effects of polluted river water in Pampanga River to the liver and gill histology of Oreochromis niloticus L. (Nile Tilapia). Water samples were collected from three selected study sites along Pampanga River namely: (1) Sucad, Apalit, (2) San Isidro, Masantol, and (3) Dalayap, Macabebe and were subjected to physico-chemical analysis. Five mature male tilapias were also collected from each site and extracted of their liver and gill tissues. These tissue samples were then assessed using various tests and indices which include hepatosomatic index (HSI), hepatocyte nucleus per mm-2 count, micro-XRF analysis, and histopathological assessment method. Qualitative histological analysis revealed alterations on the histology of both the liver and gill tissue samples which include necrosis, hemorrhage, blood congestion, hypertrophy, and hyperplasia. Among the three sites, tissues from Sucad, Apalit were observed to have the highest degree of damage. Tissues from Sucad, Apalit also garnered the highest total index for both organs and the lowest HSI for the liver tissue which further supports the mentioned observation. The physico-chemical analysis of the water samples provided the causes of the histological damage which include high level of total nitrogen and presence of heavy metals in excessive concentration. With these evidences, the level of pollution in Pampanga River definitely has an effect to the health condition of its inhabitants such as O. niloticus L.