Minimally Invasive DNA Sampling by Hemolymph Extraction Minimizes Risk to Freshwater Mussels: The Case of Endangered Unio crassus Philipsson, 1788 (Bivalvia: Unionidae)

ABSTRACT Research on endangered species is important for species conservation. Some lines of conservation research require tissue or fluids so that molecular data can be obtained. Thus, there is an increasing demand for methods of DNA sampling in endangered species that minimize harm to live animals. This especially concerns such highly threatened and protected freshwater mussels as the thick-shelled river mussel Unio crassus. With two different field experiments in Germany under natural conditions, the short- and long-term survival of Unio crassus after hemolymph extraction from the foot tissue was evaluated. We detected no negative effects in individuals of over 40 mm shell length and older than five years. We also followed some individuals for up to three years after treatment and detected no harm to these individuals. DNA quality was high and proved fully suitable for single-gene sequencing (COI) and microsatellite analyses.