Sepia officinalis: A new biological model for eco-evo-devo studies

Abstract

Lophotrochozoans are largely under-represented in ‘eco-evo-devo’. We aim to understand the evolution of cephalopods, a highly derived group in molluscan clade, in the light of the selective pressures that may be induced from their present mode of life. Sepia officinalis has been chosen for its particularities: a direct development, a complex nervous system allowing elaborated body patterning, and molluscan derived characters (brachial crown and funnel derived from the foot, internal calcareous shell). These characteristics have been selected because they confer adaptive advantages for its necto-benthic mode of life.We focus on the development of neuromuscular system that is implicated from environmental sensing to expression of complex behaviours. We study the expression during development of target genes identified using our EST library. We show that their role in S. officinalis is often different from those described in other species, as most genes show extended or restricted expression in the developing morphological novelties, or unexpected expression. Moreover, the nervous system – as well as the chromatophore network and the ability to perceive environment – differentiates very early and largely before the brain is constituted. These studies enlighten the particularities of molecular and physiological pathways in the cephalopod lineage. They underline the necessity to have a better evolutionary understanding of the genetic control of structure/function relationships.Genome sequencing on cephalopods – that possess the biggest genome among molluscs – appears crucial for comparative genomics in lophotrochozoan lineages. As S. officinalis is an ideally suitable eco-evo-devo model, we propose its genome sequencing as a priority.