Inter-species Transplantation of Blastocysts between Medaka and Zebrafish.

Transplantation of blastocysts from a donor to a host blastula constitutes a powerful experimental tool to tackle major developmental biology questions. The technique is widely implemented in diverse biological models including teleost fish, where it is typically used for intra-species blastula transplantations - i.e., labeled blastocysts into a non-labeled host to follow lineages, or mutant blastocysts into a wild-type host to address autonomous vs. non-autonomous roles of a gene of interest. We have recently implemented a protocol to transplant blastocysts between zebrafish (D. rerio) and medaka (O. latipes), two species in which blastocysts show different developmental dynamics and sizes ( Fuhrmann et al., 2020 ). We present here a detailed protocol on how to overcome the early differences in chorion structure, blastula size, and speed of development to achieve trans-species blastocyst transplantation.