Hydra are freshwater polyps widely studied for their amazing regenerative capacity, adult stem cell populations, low senescence and value as ecotoxicological marker. Many wild-type strains of H. vulgaris have been collected worldwide and maintained effectively under laboratory conditions by asexual reproduction, while stable transgenic lines have been continuously produced since 2006. Efforts are now needed to ensure the genetic characterization of all these strains, which despite similar morphologies, show significant variability in their response to gene expression silencing procedures, pharmacological treatments or environmental conditions. Here, we established a rapid and reliable procedure at the single polyp level to produce via PCR amplification of three distinct microsatellite sequences molecular signatures that clearly distinguish between Hydra strains and species. The TG-rich region of an uncharacterized gene ( ms-c25145 ) helps to distinguish between Eurasian H. vulgaris strains ( Hm-105, Basel1, Basel2 and reg-16 ), between Eurasian and North American H. vulgaris strains ( H. carnea, AEP ), and between the H. vulgaris and H. oligactis species. The AT-rich microsatellite sequences located in the AIP gene ( Aryl Hydrocarbon Receptor Interaction Protein , ms-AIP ) also differ between Eurasian and North American H. vulgaris strains. Finally, the AT-rich microsatellite located in the Myb-Like cyclin D-binding transcription factor1 gene ( ms-DMTF1 ) gene helps to distinguish certain transgenic AEP lines. This study shows that the analysis of microsatellite sequences provides a barcoding tool that is sensitive and robust for the identification of Hydra strains. It is also capable of identifying cryptic species by tracing microevolutionary events within the genus Hydra .

The polymorphism of Hydra satellite sequences provides strain-specific signatures