Cephalopods are a morphologically diverse group of mollusks with over 800 species distributed in contrasting marine environments and with complex life history modes. They display remarkable behaviors and adaptations, owned to their complex nervous system and novel morphological traits. Within decapodiformes (squid, cuttlefishes, and bobtail squid), some species present symbiotic organs: the light organ (LO) that benefits hunting and mating, and the accessory nidamental glands (ANGs) with bacteria consortium that are passed to the eggs capsule of these animals to prevent
microbial fouling.

The sequencing of new genomes and transcriptomes from bobtail squid and other closely related species is clarifying how these organs have evolved. In particular, by using a collection of several bobtail squid without LO and with LO emitting bacteriogenic and autogenic luminesce, we have elucidated when, where, and how this organ has evolved. We identified species that lost the LO independently despite living in sympatry with others emitting bacteriogenic luminesce. Autogenic luminesce is associated with pelagic lifestyles. Moreover, the loss of LO in an entire clade is closely linked with deep-sea lifestyles.

With the upcoming novel genomes from bobtail squid and other decapodiformes from different marine habitats, we expect to clarify what kind of genomic signatures are associated with the evolution of the LO in cephalopods.

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