Toxic Effects of Multiwalled Carbon Nanotubes on the Zebrafish (Danio rerio) and the Brine Shrimp (Artemia salina): a Morphological, Histological, and Immunohistochemical Study

Abstract

We describe the toxicity of multiwalled carbon nanotubes (MWCNTs) in two aquatic species: Danio rerio and Artemia salina. Fish were exposed to 25 mg L^-1, 50 mg L^-1, and 100 mg L^-1 MWCNTs for 7 days. After exposure, the gills from D. rerio showed lamellar fusion and epithelial lifting in the secondary lamellae, and vasodilation in the primary lamellae. In the gills, heat shock protein 70 and Bax (pro apoptotic member) were stained more intensely in the treated groups than in the control group. The nauplii of A. salina were exposed to 25 µg L^-1, 50 µg L^-1, and 100 µg L^-1 MWCNTs for 96 h. After exposure, the nauplii from the control group presented 20 % mortality, whereas the 25 µg mL^-1, 50 µg mL^-1, and 100 µg L^-1 groups had 46.7 %, 70 %, and 100 % mortality, respectively. The nauplii exposed to 25 µg mL¹ and 50 µg mL¹ MWCNTs had black aggregates in the intestine because of the uptake of nanomaterials. In addition, the 25 µg mL^-1 and 50 µg mL^-1 MWCNT groups had black aggregates attached onto the body surface, appendages of the second pair, and mandibles.The results revealed the toxic effects of MWCNTs on the two aquatic organisms, and both species showed great potential for toxicological evaluation of MWCNTs in aquatic environments.

Keywords:
Apoptosis; Biomarkers; Gills; Nanotoxicology

HIGHLIGHTS

Histological changes in zebrafish gills after exposed to MWCNTs;

Zebrafish gills from treated groups with MWCNTs displayed strong staining for HSP 70 and the Bax;

MWCNTs promoted mortality to Artemia salina nauplii;

MWCNTs were uptake by Artemia sallina nauplii;