The first genome size estimates for six species of krill (Malacostraca, Euphausiidae): large genomes at the north and south poles

Krill (family Euphausiidae) represent some of the most abundant organisms in the both northern and southern oceanic environments and provide food for various animals including humans. Despite their importance, little is known about krill from a genomic standpoint, even with regard to basic properties such as total genome size. This study provides genome size estimates for six species of krill from both the North Atlantic and Southern Oceans which are the first such estimates for any species of euphausiid. Genome size estimates were obtained using both flow cytometry and Feulgen image analysis densitometry with chicken and trout blood as internal standards. Haploid genome sizes ranged from 12.77 to 48.53 pg, providing roughly fourfold variation within these six species alone. With such large estimates, sequencing of a krill genome will currently be costly and laborious, but further studies should be conducted to determine the composition of these exceptionally large genomes.