AUTHORS: Cameron Haeffner, Southern Illinois University; Dr. Greg Whitledge, Southern Illinois University
ABSTRACT: Naturally occurring chemical markers in calcified structures, such as otoliths and fin rays or spines, have been commonly used in the study of fish environmental history, including identifying natal environments of wild fish, distinguishing stocked from wild fish, and inferring sources of invasive species. There are a few examples of the use of natural chemical markers in aquatic invertebrates, but this technique has not been used for crayfishes. Eye stalks have been used to estimate age of some crustaceans and may contain a microchemical record of crayfish environmental history, although this has not been tested. The objectives of this study are to determine whether crayfish eye stalks reflect microchemical (Sr:Ca, Ba:Ca) signatures of water, whether water-eye stalk microchemistry relationships differ among species, and whether this structure retains microchemical signals of previously occupied environments following crayfish transfer or molting. Four species of crayfish (Faxonius virilis, F. illinoiensis, F. luteus, and F. punctimanus) were collected from several streams in Missouri and Illinois with different water microchemical signatures. A laboratory study was also conducted in which crayfish were transferred between waters with different Sr:Ca ratios to assess signature retention. Eye stalks were sectioned and analyzed using laser ablation-ICPMS. If eye stalks contain a microchemical record of crayfish environmental history as anticipated, this technique could potentially be used to reconstruct environmental history (e.g., origin, movement) of crayfishes in the wild and may also be useful for inferring sources of non-native species.
