Whole genome duplication in the genomics era: The hidden gems in invertebrates?

Whole genome duplication (WGD) results in new potent genomic resources for rewiring the existing genetic regulatory networks in organisms. Metazoans witnessed a WGD event during the emergence of the vertebrate lineage, followed by two subsequent rounds of WGD in gnathostomes. Cyclostomes experienced a distinct and independent event of genome triplication. Furthermore, several fish lineages have also undergone varying degrees of WGD. Studying of WGDs in vertebrates are of tremendous importance to understand how these animals evolved. Recent studies are now showing different invertebrate lineages, including spiralians and ecdysozoans, have also undergone WGDs. These include WGD events revealed in certain nematode, rotifer, and snail species; as well as WGDs in the chelicerates, such as three-rounds of WGDs happened in the horseshoe crab ancestor, and one-round of WGD occurred in the last common ancestor of spiders and scorpions. Here we summarised the latest situations, and revisited the study of WGDs in different invertebrate lineages could provide new insights to better understand molecular evolution of metazoans.