Simple Summary
The Southern Pudu (Pudu puda) is the world’s smallest deer and an emblematic flagship species for South American biodiversity conservation. However, it is classified as Near Threatened due to habitat loss, road kills, and predation by feral dogs. Its reproductive biology remains largely unknown, making the preservation of its genetic resources critical. Information on pudu reproduction and embryo development could support the development of assisted reproductive technologies in this species. This study presents the first morphological description of pudu oocytes and assesses their functional competence. All oocytes were collected from a single female, limiting the generalizability of these preliminary findings. Immature cumulus–oocyte complexes (iCOCs) were collected and morphologically classified. Oocyte morphology was evaluated by measuring zona pellucida thickness, cytoplasmic diameter, and total oocyte diameter. Pudu oocytes were successfully matured in vitro and chemically activated using bovine protocols. Activated oocytes underwent cleavage at rates comparable to domestic models. However, development arrested at the morula stage, possibly reflecting species-specific culture requirements for blastocyst formation. These results provide preliminary information to support the future development of in vitro embryo production protocols for the pudu. Further studies involving more individuals are needed to determine whether these findings are representative of the wider pudu population.
Abstract
The declining pudu population highlights the need for genetic preservation strategies. This study characterized pudu oocyte morphology and evaluated in vitro competence against a bovine model. Pudu ovaries were collected from one juvenile female following therapeutic ovariohysterectomy to prevent dystocia associated with pelvic injuries. Previously adapted bovine protocols were applied. Of 26 recovered iCOCs, 6 were grade I, 14 grade II, 5 grade III, and 1 grade IV. Twenty grade I and II oocytes underwent IVM, showing significant cumulus expansion after 24 h (270.0 ± 55.9 versus 467.8 ± 93.0 µm); 70.0% reached metaphase II. Zona pellucida thickness (12.9 ± 1.1 µm), cytoplasmic diameter (124.7 ± 3.8 µm), and total diameter (159.6 ± 3.4 µm) differed significantly from bovine values. Nine matured oocytes were subjected to parthenogenetic activation (PA): 77.8% cleaved by day 2, and 33.3% reached morulae by day 5; none formed blastocysts. Bovine oocytes reached both stages. In conclusion, sampling one individual limits generalizability, as age, health, and reproductive status may influence oocyte competence. However, these results demonstrated that pudu oocytes can mature in vitro and develop to morulae following PA using bovine protocols. Culture optimization is needed to achieve blastocysts, and studies involving additional individuals are required.