Model systems

	The red flour beetle Tribolium castaneum is the second most developed genetic model system within arthropods surpassed only by Drosophila melanogaster. It represents the most species rich taxon on earth (Coleoptera) and in many respects, its biology is more typical for insects than the one of the fly Drosophila melanogaster. Technically, its major strength lies in the robust and systemic reverse genetics via RNAi gene knock-down. Further, a high quality genomic sequence is available and transgenesis and genome editing work efficiently in this species. Recently, resources for efficient mid and large scale RNAi screens have become available.
	Lymnaea stagnalis is a representative of the second largest animal phylum and is a member of the largest molluscan class, the Gastropoda. Despite their biological diversity, ancient evolutionary heritage and fascinating modes of development, molluscs are challenging to develop functional molecular tools for, and lag behind more advanced model systems in this respect. Despite these challenges L. stagnalis has long served as a model for neuroethology, eco-toxicology, morphological chirality and developmental biology. Lymnaea’s reproductive characteristics means that developmental material for study is available year-round with generation times being as short as 8 weeks. Stereotypical spiral cleaving embryos and larvae can be used to study spatial gene expression patterns, and a draft genome sequence along with a variety of transcriptome datasets are available for this species.
	Syllidae is the most diverse family of annelids characterized by its complex life cycles involving some of the most outstanding annelid reproductive strategies. Syllid reproductive modes sometimes imply the modification of the posterior body to form independent reproductive units (schizogamy) or the development of swimming adults (epigamy). Regenerative abilities are widespread in both epigamic and schizogamic syllids. All of them are able to regenerate posteriorly, while the complete anterior regeneration is more limited.
	Clytia hemisphaerica is a recently established emerging model system to study oogenesis and early embryonic development in a species at the base of animal phylogeny. A unique feature of this species is that the entire process of oogenesis can be followed by high-resolution live-cell microscopy within the isolated, transparent ovaries. In addition, the life cycle is short, including a vegetative polyp stage, which provides a continuous supply of genetically identical jellyfish, rendering this species well amenable to transgenesis. A set of recent studies have taken advantage of the assembled genome and transcriptome resources, and used this model system to revel novel features of conserved mechanism, for example, in regulation of oogenesis, origins of embryo polarity, embryonic pattering, germ-line origins or muscle evolution.
	Gnathocerus cornutus Males of the broad horned flour beetle Gnathocerus cornutus develop exaggerated mandibles. We combine comparative transcriptomics and developmental characterization, as well as RNA interference (RNAi) to identify key genes regulating mandible growth in comparison to the red flour beetle Tribolium castaneum. A draft genome, as well as RNAi are established for G. cornutus.