Gelatin capsules for post mortem vitrification of Piracanjuba (Brycon orbignyanus) ovarian tissue as an accessible solution for emergency genetic preservation

Environmental disasters have caused significant losses in fish populations, threatening the genetic diversity of many species. Cryopreservation of genetic material post-mortem has emerged as a potential solution to safeguard biodiversity. However, a fast, accessible method for cryopreserving such material in emergencies is needed. This study aims to evaluate gelatin capsules as a practical, rapid alternative to cryovials for the vitrification of fish ovarian tissue post mortem, providing an emergency method for genetic preservation. Experiments were conducted during a real-life incident where fish were found deceased. Gelatin capsules demonstrated performance comparable to cryovials in terms of oocyte viability (capsules: 68.3 ± 10.3 %; cryovials: 64 ± 5.7 %) and mitochondrial activity (capsules: 10.3 ± 4.5 AU/g; cryovials: 8.7 ± 2.7 AU/g) immediately after warming. Viability decreased after 24 h of incubation, but no significant differences were observed between treatments or containers. Histological analysis revealed minor morphological damage in capsule-vitrified oocytes immediately after warming; however, damage was equally present in both containers after 24 h. The addition of LH and FSH to the medium reduced oocyte damage, while cryovial samples without hormones showed larger cell areas (0.077 ± 0.023 mm) and perimeters (3.31 ± 0.98 mm). Gelatin capsules are a viable, accessible option for emergency cryopreservation, serving as a useful tool for preserving maternal fish genetic material under urgent circumstances. Additionally, viable primary growth oocytes were successfully obtained post mortem and remained viable after 24 h of incubation, highlighting the potential of this method for emergency genetic preservation applications.