Mucus transcriptome differs among lakes
Following exposure to crude oil, Greer et al.(2019) demonstrated that sequencing of mahi-mahi mucus was effectively able to distinguish transcriptomes of oil-exposed and non-exposed individuals. Our results from the present study expand the utility of mucus as a nonlethal sampling tool by demonstrating that sequencing of RNA in mucus can distinguish transcriptomic differences among geographically-distinct populations (Figure 2). In terms of transcriptomic similarity, individuals from L224 and L373 were most similar whereas individuals from L260 and L223 clustered apart from all other lakes (Figure 2). It should be noted that the lakes of interest in the present study are located in close proximity to one another and within the same ecozone and, thus, vary only slightly in terms of ecological conditions. Even so, unique transcriptome profiles by lake were captured within lake trout mucus indicating that sequencing of mucus is able to robustly capture gene expression changes among fish populations. Therefore, analysis of mucus may be a viable tool for ecological studies interested in assessing gene expression differences among fish populations. As mucus sampling is nonlethal and minimally-invasive, this method could be especially useful for assessing threatened and endangered populations without inducing further perturbations. Moreover, differential gene expression analysis and subsequent gene ontology analysis can be used to further elucidate transcriptomic relationships among populations and identify abiotic and biotic factors driving population differences.