Stem cells can be described as raw materials for building the bodies of organisms. Stem cells have the unique ability to build any type of specialized cells found in individual tissues. Stem cells in adults are usually no longer a tabula rasa, but they still retain part of their stemness, which was proven by scientists from the Faculty of Fisheries and Water Conservation of the University of South Bohemia in České Budějovice as per the example of common carp (Cyprinus carpio L.) produced by interspecific surrogate parents – goldfish (Carassius auratus).

Germ stem cells – male spermatogonia and female oogonia are found in gonads. These cells give rise to gametes – sperm and eggs. Male spermatogonia were successfully isolated from carp gonads and transplanted into goldfish larvae, which served as surrogate parents. In the surrogate parents, the transplanted cells resumed gamete production, and more importantly, the transplanted spermatogonia in surrogate females changed their male fate into female fate and later produced eggs carrying the male's genetic information, including sex chromosomes.

The presented study is the most distant surrogacy in vertebrates with the successful production of viable donor-derived offspring. The genera Cyprinus and Carassius diverged about 34 million years ago. If we compare the evolutionary distance to humans, then with more than a good dose of imagination, for example, a baboon could become his surrogate parent. More importantly, the production of carp offspring has been demonstrated through 10-100x smaller goldfish surrogates, opening up a novel way for conservation and propagation of genetic resources of this globally important species. At the same time, the possibilities of surrogacy in cyprinids with the potential use for the rescue of endangered members of this family were confirmed, when offspring of the endangered species can be produced through commonly bred species.

Detailed information is publicly available in the original article Franěk, R., Kašpar, V., Shah, M.A., Gela, D., Pšenička, M., 2021. Production of common carp donor-derived offspring from goldfish surrogate broodstock. Aquaculture 534: 736252.

Surrogate reproduction between common carp and goldfish. A) Microscopic caption of isolated cells from carp before transplantation. B) Cell transplantation into the body of surrogate parent by microcapillary. C) Comparison of body size between control specimen of carp and goldfish (surrogate parent) at 3 years of age.