Evaluating levels of genotoxic stress in eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) using the erythrocyte micronucleus assay

Abstract

The micronucleus assay is a count of cells containing fragments of nuclear content (micronuclei, MN) that arise duringerrorsincelldivisionand when animals are exposed to genotoxic agents such as chemicals or radiation. The assay can be performed (via light microscopy) using any nucleated cell type, such as erythrocytes in amphibians, birds, fish, and reptiles. Most prior studies of MN in amphibians have been performed in laboratory settings. The goal of this project was to determine baseline levels of genotoxic stress (i.e., frequency of MN in erythrocytes) in a free-living popu- lation of eastern hellbenders (Cryptobranchus alleganiensis alleganiensis, a species of giant salamander that lives in rocky streams) in northern Georgia, USA. We obtained and examined blood smears from 51 hellbenders from eight streams during a 3-month survey (June-August) in 2012. Counts of erythrocytes with MN were made from stained thin bloodfilmsandexpressedasapercentageoftotalcellscounted (1,000 per animal). Micronuclei were detected in 1.16 % of erythrocytes on average in the hellbenders, and there was a negative relationship between snout-vent length and MN frequency, indicating an age-related increase in clearance of cells with nuclear damage. This relationship with size should