Master “Biologie, Ecologie, Evolution”, Université de Poitiers, 2014

PhD Dissertation

Supervisors : Richard Cordaux, Clément Gilbert

Impact of a feminizing endosymbiotic bacteria (genus Wolbachia) on the evolution of terrestrial isopods sex chromosoms

Key words : sex determinism, heterogamety, sex chromosoms, DM genes, FISH, high-throughput sequencing


Terrestrial isopod crustaceans show a remarkable diversity of chromosomal sex determination systems (male heterogamety XX/XY or female heterogamety ZW/ZZ). The origin of which remains largely unknown to date. It was suggested that these systems may be the product of coevolution between terrestrial isopods and Wolbachia, a feminizing endosymbiotic bacteria transmitted vertically through oocyte.

My work aims to characterize the diversity of morphological differentiation stages of the sex chromosomes of several terrestrial isopods crustaceans species (infected or not infected by Wolbachia), and the evolutionary forces acting on these chromosomes. The results will help to assess the impact of endosymbiosis on the evolution of the host genome structure. This study is based on a combination of several approaches : bioinformatic analyzes (comparative genomic data from Illumina sequencing system), cytological studies (fluorescence in situ hybridization, karyotyping), sex reversal experiments, etc.


  1. Becking T., Mrugala A., Delaunay C., Svoboda J., Raimond M., Viljamaa-Dirks S., Petrusek A., Grandjean F., Braquart-Varnier C. (2015) Immune response of naïve crayfish to experimental infection with an introduced pathogen, Aphanomycesastaci. Journal of Immunology Research (in prep.).


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