Morphological and molecular-genetic analysis of the development of sensory organs in arthropods (Chelicerata, Myriapoda, Crustacea, Hexapoda) - a first step in understanding the generation of the diversity in the peripheral nervous system during arthropod

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The sensory system of arthropods shows a great diversity of mechano- and chemosensory receptors. To understand this diversity we need to know how the complex network of neural development has been modified during arthropod evolution. Sensory organs are mainly investigated in insects and higher crustaceans, the data on chelicerates and myriapods are limited. A detailed and consistent classification exists only for insects. The molecular processes of sensory organ development of arthropods have only been studied in insects, mainly in Drosophila melanogaster. However, there are strong arguments for the assumption of a common ancestral molecular pattern. The first step in sensory organ development is the expression of proneural genes. They enable specific cells to become neural precursor cells and are involved in the neuronal subtype specification. Homologous proneural genes were identified in all four arthropod groups. All of them are involved in the establishment of neural precursors and/or in neuronal subtype specification but partly the homologous genes are specifying different classes of sensory organs. As the combined information of gene expression patterns, gene functions and morphology is still very limited in arthropods, representatives of all 4 arthropod groups (Chelicerata: Limulus polyphemus, Cupiennius salei, Myriapoda: Glomeris marginata, Crustacea: Daphnia magna, Insecta: Tribolium castaneum) have been chosen for the investigation of mechano- and chemosensory organs using different morphological approaches (immunocytochemistry and other markers like phalloidin, Confocal Laser Scanning Microscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Light Microscopy) and comparative gene expression analysis (PCR, Standard Cloning methods, in situ hybridisation, RNA injections) of the proneural respectively neuronal subtype specifying genes achaete-scute and atonal/amos. The obtained results, which will provide data on one of the most ancestral arthropods, will contribute to the reconstruction of evolutionary development of the diversity of arthropod sensory organs.