Toward surrogate-based conservation: Preservation of
European eel (Anguilla anguilla) spermatogonial stem cells
Z. Marinović, M. Blanes-García, I. Šćekić, J. Lujić,
R.E. Balogh, L. Ferrão, M. Morini, V. Tóth, B. Urbányi, J. Kobolák, J.F.
Asturiano, Á. Horváth
Abstract
In this study, we optimized cryopreservation and
hypothermic storage protocols for the European eel (Anguilla anguilla)
spermatogonial stem cells (SSCs). As the European eel is listed as a critically
endangered fish species on the IUCN red list, there is a strong need to develop
and advance ex situ conservation strategies beyond the current
conservation measures. Cryopreservation of SSCs was done through freezing and
vitrification of testicular tissue pieces. Freezing was optimized through five
sequential experiments and has yielded SSC post-thaw viability above 50%. The
physiological competence of frozen/thawed cells was tested by transplanting
donor-derived testicular cells into sterilized common carp larvae. After two
months, gonads of 32% of the recipients displayed a positive fluorescent signal
indicating that frozen/thawed cells retained physiological competence. Needle-immersed
vitrification was optimized by testing different equilibration and
vitrification solutions. SSCs displayed viability rates above 70% after
protocol optimization. Hypothermic storage experiments displayed that storage
of isolated testicular cells is more favorable than storing testicular tissue
pieces, and that there was no significant reduction of SSC viability for 6 days
when storing them in testicular cell suspension. Results obtained in this study
are the first validated protocols for SSC preservation in the European eel and
present the foundation for biobanking and future development of surrogate-based
ex situ conservation programs for this and phylogenetically-related eel
species.
Animal Reproduction Science 292:108280. 2026
doi: 10.1016/j.anireprosci.2026.108280
