Sequence similarity tree. Sequence similarity tree of sequences amplified from krill stomachs and related sequences. The krill stomach sequences are named so as the first three letters means sampling date, i.e. M24 = March 24. 2007, S17 and S20 = September 17. and September 20. 2007, St. means Stomach number and the number in parenthesis equals the number of identical sequences of each different sequence found in the different stomachs. The tree is unrooted.