Cryopreservation of YamúBrycon siebenthalae Milt

AbstractThe yamúBrycon siebenthalae is an endemic fish of the Orinoco river basin, but wild stocks are decreasing because of the disruption of their habitat. We evaluated a protocol for the cryopreservation of yamú sperm to contribute to the preservation of this endangered genetic resource. Milt was mixed with a cryoprotectant medium (5.5% glucose, 12% egg yolk, and 5%, 10%, or 15% dimethyl sulfoxide ‐ DMSO) in a ratio 1:4 (milt:medium), stored in 0.5‐mL French straws, frozen in nitrogen liquid vapor (‐76 C), then immersed and stored in liquid nitrogen for 10 d or 12 mo. Motility of thawed spermatozoa was higher (P < 0.001) in 10% DMSO medium than 5% DMSO or 15% DMSO mediums; but lower than the control (P < 0.001). With sperm cryopreserved, the highest level of fertilization was achieved with 10% DMSO (P < 0.001) after 10 d or 12 mo of cryopreservation. Fertilization of eggs inseminated with 6.4 × 109 spermatozoa per g of eggs was higher (P <0.05) than with 1.6 × 109 spermatozoa per g of eggs. There was no difference (P > 0.05) in fertilization between insemination doses of 3.2 × 109 and 6.4 × 109 spermatozoa per g of eggs. Cryopreservation of yamu milt can be performed successfully with a simple medium combined with 10% of DMSO as cryoprotectant. The highest level of fertility was achieved using between 3 × 109 and 6 × 109 spermatozoa per g of fresh eggs.