Karyotyping and single-gene detection using fluorescence in situ hybridization on chromosomes of Hydra magnipapillata (Cnidaria: Hydrozoa)

The fresh water polyp Hydra L., 1758 (Cnidaria, Hydrozoa) plays a key role as a model organism in modern evolutionary and developmental biology. A complete genome sequence has been published recently for Hydra magnipapillata Ito, 1947 and molecular data are rapidly accumulating in the literature, but little information is avail- able on its chromosomes. In this study, an effi cient fl uorescence in situ hybridization (FISH) method is described for H. magnipapillata which not only allows identifi cation of the chromosomes but also visualization of the location of individual genetic loci. Together with cDNA and genomic sequencing this may provide the foundation for in- creasingly precise genetic and physical mapping in this basal metazoan model organism.