Determinations of Erythrocyte Sizes in Adult Pelophylax ridibundus (Amphibia: Anura: Ranidae) Inhabiting Industrial Area in Southern Bulgaria

Abstract

In this study, basic erythrocyte sizes in P. ridibundus individuals inhabiting a polluted area (heavy metals, nitrates, nitrites, and ammonium) in southern Bulgaria were evaluated. The erythrocyte cells’ parameters, erythrocyte length (EL), erythrocyte width (EW), length/width ratio (EL/EW), and erythrocyte size (ES), and nuclear parameters, nucleus length (NL), nucleus width (NW), NL/NW ratio, nucleus size (NS) and NS/ES ratio were either measured or calculated. The data obtained were compared with the data from identical measurements made in frogs inhabiting a reference site. In this study, an authentic reduction was established, of the basic erythrocyte-metric cells (EL, EW, EL/EW ratio, and ES) and nuclear (NL, NW, NL/NW, and NS) parameters in P. ridibundus individuals that inhabit the polluted industrial area east of the city of Plovdiv. In those frogs’ blood, oval and spherical erythrocytes circulate. For the erythrocytes from frogs in the polluted site, a significant reduction was found in the nucleus/cytoplasm ratio. Those changes can be seen as adaptations enlarging the contact surface and the oxygen capacity of the erythrocytes in conditions of hypoxia. The results of our research once again emphasize the importance of hematological investigations and specifically of the blood cell morphology as reliable biomarkers in ecotoxicological research in the field.