XY sex determination in a cnidarian.

Background: Sex determination occurs across animal species, but most of our knowledge about its mechanisms comes from only a handful of bilaterian taxa. This limits our ability to infer the evolutionary history of sex determination within animals.

Results: In this study, we generated a linkage map of the genome of the colonial cnidarian Hydractinia symbiolongicarpus and used it to demonstrate that this species has an XX/XY sex determination system.

CRISPR/Cas9-mediated gene knockin in the hydroid Hydractinia symbiolongicarpus.

Background: Hydractinia symbiolongicarpus, a colonial cnidarian, is a tractable model system for many cnidarian-specific and general biological questions. Until recently, tests of gene function in Hydractinia have relied on laborious forward genetic approaches, randomly integrated transgenes, or transient knockdown of mRNAs.

Results: Here, we report the use of CRISPR/Cas9 genome editing to generate targeted genomic insertions in H.