Heavy Metal Accumulation in the Tissues and Organs of Pelophylax ridibundus (Pallas, 1771) and Pelophylax lessonae (Camerano, 1882) (Amphibia: Ranidae) Living in the Waterbodies of Nizhniy Novgorod

A comprehensive atomic-emission study and comparative assessment were done of the content and distribution of heavy metals (Mn, Cu, Cr, Al, Fe, Zn, and Sr) in the organs and tissues (muscles, skin, bones, gonads, liver, heart, spleen, and blood) of marsh and pool frogs collected in the lakes of a big industrial city (Nizhni Novgorod). High concentrations of heavy metals were found in the spleen (Cr), bones (Zn and Sr), liver (Cu) of lake frogs. High coefficients of the biological absorption of Mn, Sr, Zn (bone tissue), Fe (liver, spleen), and Cu (heart) were found in pool frogs. The cumulative properties of heavy metals were estimated from the accumulation coefficient established. Species regularities of heavy metal accumulation from water are presented in descending order as the following series: Zn > Cr > Al > Cu > Fe > Sr > Mn for pool frogs; and Fe > Zn > Mn > Cu > Cr > Al > Sr for marsh frogs. The priority intake of chromium, manganese, aluminum and strontium from the aqueous medium into the body occurred through the skin. Active zinc accumulation occurred mainly through food, which was confirmed by high values of the biological absorption coefficient of zinc for the liver of Pelophylax ridibundus and Pelophylax lessonae. The dependence of the heavy metal accumulation in the muscles from the organs in contact with the external environment (skin) and the digestive system (liver) was established by regression analysis. The most important adaptation of tailless amphibians is their ability to prevent excessive accumulation of heavy metals in their body, while living in the conditions of increased environmental pollution. Our results obtained speak for the high accumulation of heavy metals in the body of tailless amphibians, determined by the conditions of the aquatic environment and the bioavailability of these metals.