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Developmental and descriptive study of the tegumentary structures involved in colour patterning in <i>Sepia officinalis</i>

Team 2: Reproduction and development of aquatic organisms: evolution, adaptation, regulations


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Coleoid Cephalopods (cuttlefishes, squids, octopuses) are the organisms with the most developed abilities to change their shape and colour, mostly for communication and camouflage. Their integument possesses three specific cellular structures, namely chromatophores (neuromuscular and pigmentary organs), iridophores (providing iridescence) and leucophores (providing the white background of patterns). This work applied different approaches (biochemistry, histology and genetic), in Sepia officinalis, to study the development of these structures and to understand how colour patterns have closely evolved with both life history and ecological niche in each coleoid group. Regarding chromatophores, we describe their developmental dynamic. A link between FMRF-amide neurons and chromatophore development is discussed. RSE analysis tends to confirm the presence of melanins in chromatophores. The difficulty to investigate the development of chromatophores (through ARN expression) is described and discussed. Regarding iridophores (the optical properties which are due to the production of specific proteins called reflectines), we describe their developmental dynamic for the first time. We demonstrate the occurrence of six different reflectin genes in S. officinalis and show that their expression is not tissue or organ specific. Reflectin genes in other cephalopod species have been sequenced and our preliminary phylogenetical analyse point up a complex evolutionary history with the potential diversification of three putative ancestral reflectin forms.
Key words: Sepia officinalis, cephalopod, development, chromatophore, iridophore, reflectin

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