Ingested Polypropylene Microplastic Induces Increased Appetite, Weight Gain and Haematological Response in African Catfish (Clarias gariepinus)

Abstract

Polypropylene (PP) microplastic toxicity of biological systems has not been exhaustively investigated; therefore, the objective of this paper was to assess the effects of Polypropylene (PP) on feeding habit (appetite), dry weight and blood parameters such as red blood cell (RBC), white blood cell (WBC), haemoglobin (Hb) and haemtocrit levels (HCT) in African Catfish exposed to PP for 50 days using appropriate standard methods. The results showed that PP induced strong appetite in all the treatments for the first 30 days, followed by the reluctance to feed, particularly in the 2 g/kg PP-fish meal treatment. Interestingly, the Catfish fed with 0.8 g/kg PP-fish meal gained weight significantly (3.6 ± 0.22 g) compared to the control (1.6 ± 0.33 g) by day 50. This obesogenic potential of PP is suggested to be caused by disruptions of the fish’s lipid metabolism. To the best of our knowledge, this study is the first to report PP-induced weight gain in African Catfish (at relatively low PP concentrations) in contrast to previous studies. Furthermore, haematological changes occurred in a dose-dependent fashion where the RBC, Hb and HCT significantly decreased (5.6 x 10¹²/L, 14.8 g/L and 38%, respectively) compared to the controls (7.9 x 10¹²/L, 16.8 g/L and 44%, respectively) while WBC significantly increased (19.54 x 10⁹/L) compared to the control (13.44 x 10⁹/L) in the 2 g/kg PP-fed treatments by day 50, indicating anaemia and weak immunity. This study highlights the implication of PP microplastic exposure to aquatic ecosystems and the urgent need for plastic reduction.