Fig 4. Phylogenetic and geographical distribution of QAE isoforms.

A) Phylogenetic tree of the complete QAE subgroup from S4 Fig. Sequences are indicated as in Fig 2 and sequential tandemers from Antarctic eelpout are labelled alphabetically (e.g. Antarctic-eelpout-Q3a, Antarctic-eelpout-Q3b). Sequences from northern fish are on a green background while those from southern fish are on pink. The scale bar represents an average of 0.02 changes per site and bootstrap values (percent) are indicated at most nodes. B) A newly-discovered Pachycara sp., found during the 2016 NOAA Okeanos expedition at the Mariana Trench, 18°27ʹ N; 147°50ʹ E, in 1.5°C waters below 4000 m (https://service.ncddc.noaa.gov/rdn/oer-rov-cruises/ex1605l3/#tab-20). C) Diagram of a cold-water migration route through a cross-section of the oceans from the Arctic to the Anarctic. The deep water passage shown by the dotted arrows through the tropics avoids warmer surface waters (red).