Evolutionary genomics of the crustacean Triops cancriformis (Branchiopoda, Notostraca)

WHO? Triops cancriformis is a crustacean of the class Branchiopoda, order Notostraca. The order comprises only two genera (Triops and Lepidurus) world-wide distributed owing to their ancient origin. T. cancriformis lives in freshwater ponds that may be subjected to dry period during which the tadpole shrimps survive as encysted egg resistant stages. It is also well known for its high morphological stasis, compared with fossil forms; hence the debated status of "living fossil". WHY? Aside from the peculiar morphological stasis, T. cancriformis represents an interesting framework to address evolutionary studies: i) across its European range it is present with bisexual, parthenogenetic, hermaphroditic and androdioecious populations: it would be, thus, interesting to check whether di erent reproductive strategies leave genomic signatures such as di erential evolutionary rates and/or trans- posable element accumulation; ii) Branchiopod crustaceans are phylogenetically close to Hexapoda, in most analyses resulting their sister clade. The study of T. cancriformis genomic features in comparison with those of early-branching Hexapoda could tell about the origin of hexapods and their most represented taxon, Insecta. HOW? Genomic resources on T. cancriformis and related species are slowly accumulating (transcriptomes, RAD-sequencing and one genome draft), although a comprehensive and co-or- dinated project of a genomic evolutionary study is still lacking. We therefore, undertaken Illumina sequencing of T. cancriformis genomes, starting from Italian parthenogenetic samples and Spanish bisexual ones. Moreover, we included two species from the related genus Lepidurus (L. apus lubbocki and L. arcticus) in order to have a clearer picture of Notostraca genomes. Further sequencing will be performed on transcriptome and already published data will be also included in the analyses. TO GET WHAT? A total evidence picture on the hardwares (genomes) and softwares (transcriptomes) evolution, with a special focus on repetitive DNA (transposable elements and satellite DNA), in the same species presenting genomes subject to di erent reproductive milieau. We have already some results indicating that transposable elements (R2 lineages) are di erently evolving in di erent T. cancriformis genomes. The full genome sequencing of further population/ species will help drawing a more complete picture, including the possibility to study all transposable element lineages as well as satellite DNAs. Moreover, the strengthening of the genomic dataset with new branchiopod species will likely result in a more stable phylogenetic relationship of Branchiopoda with closer taxa. Finally, we will get knowledge on the genome structure and composition that will be compared with the close relatives, the Hexapoda.