List of Accepted Abstracts

The phylum Arthropoda is the largest and most diverse group of animals on the planet, representing about 80% of all known animal species, encompassing spiders, crustaceans, insects, and numerous other species. However, comparative genomic studies within the subphylum Pancrustacea have focused predominately on the insect clade (Hexopoda). As such, we lack a clear understanding of what constitutes an “insect” versus a “crustacean” genome relative to other arthropod subphyla. Here, we present our preliminary analyses on the characteristics of arthropod genomes. We analyzed 75 Arthropod genomes (15 Chelicerates, nine Myriapods, and 51 Pancrustacean genomes), along with two Tardigrade outgroups. We found intriguing differences in genomic characteristics among arthropods. First, high AT-richness across all arthropod subphyla was found. While insect genomes had been noted for being AT-rich, we found that genomes of chelicerates (minus the parasitiforms) were even more AT-rich, and crustaceans significantly less so. This pattern was particularly true for non-coding DNA sequences, but much less so for coding sequences. The fact that non-coding sequences tended to be far more AT-rich than coding sequences for all arthropod subphyla suggests that neutral processes drive the AT-richness in arthropod genomes, while purifying selection suppresses the AT-richness in coding sequences. Second, chelicerates showed an inverse relation between genome size and AT-richness of the 3rd codon. In contrast, crustaceans and insects exhibited positive relationships. AT-richness and genome size have been found to be negatively correlated in some taxa, including in specific bacterial phyla, but the pattern varies considerably in animals. Third, gene families specific to insects alone include odorant binding proteins and odorant receptors, potentially related to terrestrial colonization by insects. We also annotated previously unknown crustacean gene families and elucidated evolutionary patterns of several gene families related to environmental adaptation. Our results are a first step toward revealing the evolutionary forces that shape the genome architectures of arthropod lineages and uncovering the association with ecological factors.