Fig. 1

Overall size and genomic organization of arthropod Hox genes varies. On the left is a representative phylogenetic tree depicting relationships among the arthropod taxa used in the comparative analysis, as depicted in [32, 100–102]. Mus musculus is used as an out-group. Colored boxes represent Hox genes (and mice homologs according to [103]) and miRNAs, with numbers to the right of the black line indicating approximate size of the genomic region displayed for individual taxa. All Hox genes are depicted in the same transcriptional orientation, except where indicated with a red arrowhead. Data on inversions within the Anopheles Hox cluster are conflicting, as published data only show a single microinversion of ftz [13, 14, 21]; however, the most recent genome assembly shows a large inversion from labial to Deformed as depicted here. Broken lines indicate large genomic spans in Bombyx (12 Mb from lab to pb, with 9.9 Mb removed here for ease of view), Drosophila (9.7 Mb from Antp to Ubx, with 6.7 Mb removed here for ease of view), and Tetranychus (2.9 Mb from pb to Dfd). The Anopheles, Tribolium, Nasonia, Apis, and Mesobuthus Hox gene clusters are depicted at 1/2 scale (denoted by the horizontal blue line), the Drosophila, Bombyx, Ixodes, and Tetranychus Hox gene clusters at 1/6 scale (denoted by the horizontal red line), and the Metaseiulus Hox gene cluster at 1/20 scale (denoted by the horizontal purple line). The number of intervening protein coding genes between Hox genes is indicated by horizontal line thickness. Numbers to the right indicate the respective length of the Hox clusters in the genome in megabase pairs (Mb), as calculated from the transcriptional start of the most 3′ Hox gene to the transcriptional stop of the most 5′ Hox gene, and the proportion of the genome that contains the Hox cluster is indicated as a percentage along with the genome size in parentheses, respectively