van Tartwijk, F. W.; Marty, A.-P. M.; Rahmani, A.; Jia, Y.; Ward, E. N.; Hussain, I.; Peck, L. S.; Kaminski, C. F.; Clark, M. S.

In the Antarctic Southern Ocean, cold-blooded animals have evolved to live at stable temperatures of 0{+/-}2 {degrees}C. This extremely low temperature affects their biology at every scale, from protein folding to development. However, how animal (sub)cellular organisation and dynamics are adapted to near-0 {degrees}C temperatures has not been studied. We therefore established methods to culture and fluorescently label cells from the Antarctic plunderfish Harpagifer antarcticus and a temperate comparator species, the shanny Lipophrys pholis. By imaging these cultures live at physiological temperatures, we found that subcellular organisation is broadly conserved in H. antarcticus, featuring known membranous organelles and biomolecular condensates that remain dynamic, with mitochondria in H. antarcticus and L. pholis moving at similar speeds. However, we also identified differences in organelle properties between H. antarcticus and L. pholis, including lysosomal enlargement and mitochondrial morphology changes. These differences may be functionally linked to protein misfolding and slow embryonic development in Antarctic species.