Exome capture of Antarctic krill (Euphausia superba) for cost effective population genetics of historical collections

Abstract

Antarctic Krill (Euphausia superba) is a pivotal keystone species in the Southern Ocean ecosystem, with immense ecological and commercial significance. However, its vulnerability to climate change necessitates urgent investigation of its population genetics and adaptive responses. Historical spirit collections of Antarctic krill from the early 20th century represent an ideal opportunity for genomic research, to investigate how krill have changed over time and been impacted by predation, fishing and climate change. In this study, we assessed the utility of shotgun sequencing and exome capture for genomic analyses with historical spirit collections of Antarctic krill. Because the krill genome is very large (48Gb) two full-length transcriptomes were generated and used to identify putative targets for targeted resequencing. Skim genome sequencing allowed sample and library quality control. By comparing genome to exome resequencing of the same libraries we calculate enrichment and variant calling metrics. Full-length mitochondrial and nuclear ribosomal sequences were successfully assembled from genomic data demonstrating that endogenous DNA sequences could be assembled from historical collections. We find that exome capture provided enrichment of on-target sequence data, with increased depth and higher variant quality for targeted loci. Our findings demonstrate the feasibility of extracting genomic information from historical krill samples, despite the challenges of fragmented DNA and huge genome size unlocking such collections to provide valuable insights into past and present krill diversity, resilience, and adaptability to climate change. This approach unlocks the potential for broader genomic studies in similar samples, and for enhancing conservation efforts and fisheries management in the Southern Ocean ecosystem.