Microplastics-Induced Eryptosis and Poikilocytosis in Early-Juvenile Nile Tilapia (Oreochromis niloticus)

Abstract

This study aims to assess the impact of microplastics (MPs) on erythrocytes using eryptosis (apoptosis) and an erythron profile (poikilocytosis and nuclear abnormalities), considered to be novel biomarkers in Nile tilapia (Oreochromis niloticus). In this study, four groups of fish were used: The first was the control group. In the second group, 1 mg/L of MPs was introduced to the samples. The third group was exposed to 10 mg/L of MPs. Finally, the fourth group was exposed to 100 mg/L of MPs for 15 days, following 15 days of recovery. The fish treated with MPs experienced an immense rise in the eryptosis percentage, poikilocytosis, and nuclear abnormalities of red blood cells (RBCs) compared with the control group in a concentration-dependent manner. Poikilocytosis of MP-exposed groups included sickle cell shape, schistocyte, elliptocyte, acanthocyte, and other shapes. Nuclear abnormalities of the MPs-exposed groups included micronuclei, binucleated erythrocytes, notched, lobed, blebbed, and hemolyzed nuclei. After the recovery period, a greater percentage of eryptosis, poikilocytotic cells, and nuclear abnormalities in RBCs were still evident in the groups exposed to MPs when crosschecked with the control group. The results show concerning facts regarding the toxicity of MPs in tilapia.

Keywords: Oreochromis niloticus; apoptosis; erythrocytes; microplastics; poikilocytosis; tilapia.

Figure 1

Percentage of apoptotic cells of early-juvenile tilapia (Oreochromis niloticus) exposed to microplastics (MPs). Data are presented as mean ± SE. Bars with different superscript letters are significantly different (P < 0.05) (n = 6).

Figure 2

Apoptosis detection in early-juvenile tilapia (O. niloticus) after exposure and the recovery to control conditions and MPs at 1, 10, and 100 mg/L. The cells fluorescing light green after staining with acridine orange was considered apoptotic, while normal cells were pale green. Red circles indicate apoptotic cells and yellow circles indicate nonapoptotic cells. (Scale bar = 50 μm).

Figure 3

Hematoxylin and eosin-stained blood smears from juvenile O. niloticus showing I; MP exposure: normal erythrocytes (A), deformed ones after exposure to MPs at 1 mg/L for 15 days (B), deformed ones after exposure to MPs at 10 mg/L for 15 days (C,D), and deformed ones after exposure to MPs at 100 mg/L for 15 days (E,F) and II; recovery period: normal erythrocytes (G), deformed ones after recovery from exposure to MPs at 1 mg/L for 15 days (H), deformed ones after recovery from exposure to MPs at 10 mg/L for 15 days (I), and deformed ones after recovery from exposure to MPs at 100 mg/L for 15 days (J). Tr, tear-drop cell; Cr, crenated cell; Ac, acanthocyte; Ecn, eccentric nucleus; Kn, kidney shape; Hr, heart shape; Eli, elliptocytes; odd, odd shape; FL, filamented; Shc, schistocytic and Sk, sickle cell.

Figure 4

Hematoxylin and eosin-stained blood smears from juvenile (O. niloticus) showing nuclear abnormalities, I; MP exposure: normal erythrocytes (A), deformed ones after exposure to MPs at 1 mg/L for 15 days (B,C), deformed ones after exposure to MPs at 10 mg/L for 15 days (D–G), and deformed ones after exposure to MPs at 100 mg/L for 15 days (H–L) and II; recovery period: normal erythrocytes after recovery from exposure to MPs for 15 days (A), the deformed ones after recovery from exposure to MPs at 1 mg/L for 15 days (B), deformed ones after recovery from exposure to MPs at 10 mg/L for 15 days (C–E), and deformed ones after recovery from exposure to MPs at 100 mg/L for 15 days (F–H). Bn, blebbed nucleus; En, elongated nucleus; Non, notched nucleus; Mn, micronucleus; Bin, bionuclei; Kn, kidney-shaped nucleus; Irn, irregular nucleus; Lon, lobed nucelus; Rox, rouleaux shape; Eln, elongated nucleus.