NoteHepatic and renal metallothionein concentrations in Commerson's dolphins (Cephalorhynchus commersonii) from Tierra del Fuego, South Atlantic Ocean

•The first report on MT contents in liver and kidney of subantarctic dolphins•MT levels are not correlated with toxic metal concentrations measured in the tissues.•MT levels are closely related to homeostasis of essential metals and correspond to the background physiological ranges.•The assessment can be considered as baseline for the species health issue conservation.

The Commerson's dolphin is the most common endemic odontocete of subantarctic waters of Tierra del Fuego, Argentina incidentally caught in fishing nets. The species is classified as “Data Deficient” by the IUCN. Metallothioneins (MTs) are considered as suitable biomarkers for health and environmental monitoring. The aims of the study were to assess MT concentrations in the liver and kidney of bycaught specimens. Moreover, correlations with Zn, Se, Cd, Ag and Hg, and the molar ratios of MT:metals were estimated to evaluate if there is an indication of their respective protective role against metal toxicity in tissues. Hepatic and renal MT concentrations were similar, ranging from 11.6 to 29.1 nmol·g− 1 WW, and Kidney/Liver ratios ranging from 0.73 to 1.93 corresponded to normal ranges. Results suggest that MTs are related to physiological ranges for the species. This information constitutes the first MT report on Commerson's dolphins and possibly considered as baseline for species' conservation.