Genomic and transcriptomic analyses of an endoparasitic crustacean with an highly simplified adult morphology, Sacculina carcini

A few arthropods evolved towards an endoparasites and show a dramatic change in body shape and anatomy, often barely resembling arthropods at all. The parasitic barnacle Sacculina carcini (Crustacea: Rhizocephala) is one prominent example in evolutionary transformation due to an endoparasitic lifestyle. The adults show no sign of their arthropod kin: segmentation, appendages and most of the internal organs usually found in arthropods are completely missing. The adult body is divided into two parts: a network of rootlets growing in the body cavity of the crab hosts and a temporary breeding sac, bearing gonads and keeping first larval stages. There is a good record of studies on morphology and life cycle, but almost nothing is known about the genome of rhizocephalan species. This project aims to get a better understanding about the genetic and genomic foundations of this extreme modification of morphology. We focus on the finishing of the genome of Sacculina carcini and transcriptomic characterisation of rootlets and breeding sac. In a comparison to the standard repertoire of other arthropod genomes we will show which genomic transformations accompany the morphological simplification. Gene content as well as regulatory effects will be compared to get a better understanding of evolutionary transformations on the genomic level. One focus is the repertoire of transcription factors present in the genome and active in developmental stages and organs. Transcriptomic profiles of adult tissues will as well be compared to gain deeper insight into the evolutionary processes of morphological change and the switch to parasitism.