In vitro fertilizations with cryopreserved sperm of Rhinella marina ( Anura : Bufonidae ) in Ecuador

—Considering worldwide amphibian population decline, sperm cryopreservation should be a priority for conservation of species in areas of high biodiversity, such as the Neotropics. In this study, we present the results of two cryopreservation experiments involving Rhinella marina sperm. Freezing was performed in a -80 °C freezer and dimethyl sulfoxide (DMSO) was used as cryoprotective agent. In the first experiment, the effects of 5%, 10%, and 15% DMSO were evaluated in sperm lysis and fertilization capacity. Samples were incubated for 10 minutes at 4 °C before freezing. For thawing, two procedures were tested: 21 °C thawing to be used immediately and 4 °C thawing, to be used two hours later in in vitro fertilizations. The best treatment was 10% DMSO plus thawing at 4 °C, that achieved 20% successful fertilizations. In the second experiment, two solutions were tested: 10% DMSO with and without HEPES. Freezing and post-thawing in vitro fertilizations were performed after a two hour incubation period at 4 °C. A considerable improvement in fertilization percentages was obtained in this experiment, with a 75% for DMSO alone, and a 70% for DMSO + HEPES. These results provide good perspectives for future implementation of sperm cryopreservation in Neotropical institutions for local threatened species.

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