Gustavo Sanchez

TL;DR: This article found that the genomes of soft-bodied (coleoid) cephalopods are highly rearranged relative to other extant molluscs, indicating an intense, early burst of genome restructuring.

TL;DR: This study identifies unresolved phylogenetic relationships within the cephalopod phylogeny and insufficient taxonomic sampling among squids excluding the Loliginidae in the Decabrachia and within the Order Cirromorphida in the OctobRachia.

Abstract: Bobtail and bottletail squid are small cephalopods with striking anti-predatory defensive mechanisms, bioluminescence, and complex morphology; that inhabit nektobenthic and pelagic environments around the world’s oceans. Yet, the evolution and diversification of these animals remain unclear. Here, we used shallow genome sequencing of thirty-two bobtail and bottletail squids to estimate their evolutionary relationships and divergence time. Our phylogenetic analyses show that each of Sepiadariidae, Sepiolidae, and the three subfamilies of the Sepiolidae are monophyletic. We found that the ancestor of the Sepiolinae very likely possessed a bilobed light organ with bacteriogenic luminescence. Sepiolinae forms a sister group to Rossinae and Heteroteuthinae, and split into Indo-Pacific and Atlantic-Mediterranean lineages. The origin of these lineages coincides with the end of the Tethys Sea and the separation of these regions during the Eocene and the beginning of the Oligocene. We demonstrated that sepiolids radiated after the Late Cretaceous and that major biogeographic events might have shaped their distribution and speciation. Sanchez, Rokhsar, and colleagues use genome skimming to generate DNA markers for phylogenomic analyses of bobtail and bottletail squid. The ancestral state of bioluminescence suggests that the Sepiolinae ancestor possessed a bilobed light organ with bacteriogenic luminescence. Also, analyses of divergence time suggest that major biogeographic events might have shaped the speciation of these animals.

TL;DR: Differences in the spatial and bathymetric distributions of these two species might reflect differences in temperature preference, spawning depth, and migration patterns.