Cryopreservation of Centropomus viridis gonadal tissue: A key step for conservation and aquaculture in Mexico.

The snook (Centropomus viridis) has a significant economic impact in Mexico's northern Pacific coastal region. Germ cell (GCs) cryopreservation is used as a strategy for species conservation due to its ability to transfer genetic information, promote self-renewal, and facilitate cellular differentiation, ensuring the propagation of the species. In this work, we present a protocol for the cryopreservation of gonadal tissue from juvenile snook (C. viridis). Gonadal tissue disaggregation was performed using trypsin (0.25 %, 0.30 %, 0.40 %, or 0.50 %). GCs were isolated using a Percoll density gradient (10 % and 40 %). Cryopreservation was performed using ethylene glycol and dimethyl sulfoxide (DMSO) at concentrations of 1.5 M or 2 M or the combination of 1.5 M DMSO, lactose (0.1 or 0.2 M), and 10 % egg yolk. Freezing was performed at -80 °C for 10, 15, or 30 min. GCs were identified using vasa by immunocytochemistry. Cell viability and concentration were assessed. Trypsin at 0.25 % resulted in a 98.25 ± 1.0 % cell viability. GCs were isolated from the 10 % Percoll band, with 36 % of the cells expressing vasa. Gonadal tissue cryopreserved with 2 M DMSO at -80 °C for 15 min exhibited the highest cell viability, with 71.83 ± 2.47 %. The results establish a baseline for guiding future cryopreservation efforts involving gonadal tissue from other marine fish species.