Meeting Abstract
Coleoid cephalopods (squids or octopuses), these primates of the seas, have been viewed as remarkable illustrations of independent origins of complex neural and sensory structures as well as highly centralized brains in invertebrates. Here, we will discuss three examples of convergent evolution of the neural organization: (i) Cephalopod eyes and visual system including optic lobes; (ii) Specialized parts of the brain controlling learning and memory such as vertical lobes (considered to be analogs of mammalian hippocampus); and (iii) Unique cephalopod vasculature to support such brain complexity. We performed deep sequencing of genomes and transcriptomes form five cephalopod species including Nautilus to decipher molecular bases of these critical examples of convergent evolution in a broad sense. In addition to comparative RNA-seq analysis across species, we also explored the dynamics of gene expression in the development of both Nautilus and squids. The data from Nautilus are most essential. Indeed, Nautilus has a simpler cord-like neuronal organization resembling a basic molluscan tetraneury and its embryos are amongst the most elusive in the animal kingdom. By combining phylogenomics, comparative transcriptomics and in situ hybridization approaches on representatives of several molluscan species, we will discuss the use of various molecular markers to trace both cephalopod neuronal innovations and possible homologous cell lineages within molluscs. We will also outline gene regulatory changes associated to lens and vascular development and briefly review our efforts to identify cephalopod novelties.
