Accuracy and reliability of Dreissena spp. larvae detection by cross-polarized light microscopy, imaging flow cytometry, and polymerase chain reaction assays

Abstract

The expansion of Dreissena spp. mussels into the western United States has generated an increased need for reliable early detection methods, especially for larvae (veligers), which are a primary transport vector and an indicator of spawning adults. Cross-polarized light microscopy (CPLM) currently provides the most reliable means for detecting quagga and zebra mussel (Dreissena spp.) larvae in plankton samples. In this study a double-blind experiment was undertaken to assess the current reliability of 3 different methods for detecting Dreissena spp. larvae in plankton samples. Methods included CPLM, imaging flow cytometry (IFC), and DNA-based polymerase chain reaction (PCR) assays. We distributed 216 reference samples consisting of concentrated plankton spiked with known numbers of Dreissena spp. larvae to 19 laboratories for analysis. Results indicated that presence/absence detection CPLM was the most reliable (96.3% accuracy), IFC analysis was next most reliable (91.7% accuracy), and PCR was the least reliable (75.8% accuracy). The most prevalent type of error associated with all the methods was false negatives, suggesting that all methods are more likely to fail to detect the presence of larvae rather than to falsely indicate their presence.