engleski

Selenium concentrations in tissues of striped (Stenella coeruleoalba), risso’s (Grampus griseus) and bottlenose dolphins (Tursiops truncatus) from the Croatian Adriatic coast

Selenium (Se) is an essential element that plays an important role in many biological processes in humans and animals. In mammalian tissues, antioxidants such as Se protect against oxidative stress. It acts primarily within selenoproteins, indirectly affecting oxidative stress induced by cadmium and mercury. However, the element can be toxic to mammals at high concentrations and causes several pathological conditions, such as cancer, coronary heart disease and liver necrosis. In the present study, Se concentrations were determined in the tissues of three dolphin species. Stranded cetaceans were sampled along the Croatian Adriatic coast between 1999 and 2003: 23 bottlenose dolphins (Tursiops truncatus), 8 striped dolphins (Stenella coeruleoalba) and 6 Risso’s dolphins (Grampus griseus). Selenium concentrations in muscle, kidney and liver tissues were determined using graphite furnace atomic absorption. Selenium levels in dolphin tissues were measured in the ranges (mg/kg): muscle 0.001–81.9 ; liver 3.13–1197 ; kidney 0.55–137. The highest levels measured were: 23.6 mg/kg in kidney of T. truncatus, 28.9 mg/kg and 529 mg/kg in muscle and liver of G. griseus. The lowest Se concentrations were determined in the tissues of S. coeruleoalba (mg/kg): 5.34 in muscle, 6.63 in kidney, 100 in liver. Significant differences in Se levels between species were found. Significantly higher Se levels were determined in muscle, liver and kidney of G. griseus and T. truncatus than in S. coeruleoalba (p<0.05, all). In comparison with previous reports from the Ligurian Sea in Italy, Se levels in the present study showed variability in all tissues of T. truncatus and S. coeruleoalba. In the present study, Se measured in the liver of G. griseus was 1.5 to 2 times higher than those monitored at three locations in the Mediterranean and southern Adriatic Seas. Variations of Se in dolphin tissues is evidently related to geographic area.

Selenium; Tissues; Three dolphin species; Croatian Adriatic coast

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