Alignment of the five major copy types of alpha tubulin in bdelloid rotifers. Classes based on intron presence/absence. Black block = exon, grey block = intron, line = gap. Copy classes 4, 5 and 3 contained variants with introns indicated by a, b and c respectively that were absent in copies otherwise sharing the same intron structure. Numbers of copies in each species are shown: A. ricciae (Ar), A. vaga (Av), M. quadricornifera (Mq) and P. flaviceps (Pf).