Length Reduction of Larval Yellow Perch and Freshwater Amphipods in RNAlater Solution

Abstract

Use of RNAlater (Ambion, Inc.) solution to preserve whole organisms for nucleic acid analysis is gaining popularity, in part because it effectively preserves both RNA and DNA without the need for freezing the organism. Similar preservatives have been shown to cause short-term changes in animal length, and such changes must be accounted for as analyses progress. We examined the rates and degrees of shrinkage for freshwater amphipods Diporeia spp. and larval yellow perch Perca flavescens after preservation in RNAlater solution in comparison with more common preservatives. We found that after 2 months of preservation, Diporeia shrank by 3% in RNAlater versus gaining length by 5% in diluted ethanol and by 1% in diluted formaldehyde. After 5.5 months of preservation, larval yellow perch lengths decreased by 23% in RNAlater, 10% in diluted ethanol, 12% in diluted formaldehyde, and 19% when frozen in water. Overall length reduction for Diporeia and larval yellow perch was significantly greater in RNAlater than in ethanol or formalin. Since accurate measures of length are necessary for many nucleic acid analyses, researchers utilizing RNAlater solution should attempt to measure organisms while they are alive or should develop preservation-specific correction functions to overcome biases associated with shrinkage.