Storage and transportation of Prochilodus lineatus (Characiformes) sperm prior to cryopreservation

In this study we compared post-thaw quality of P. lineatus sperm frozen shortly after collection, with sperm frozen after dilution and transportation, and up to 6 h from collection. From each sperm sample (n = 10 males) five aliquots were taken. One aliquot was diluted in the freezing medium (1 sperm:8 glucose:1 methyl glycol) and frozen ∼20 min after collection in the field (control), while the other four aliquots were transported to the laboratory where freezing took place 3 or 6 h after collection. From the transported aliquots, two were diluted 1:4 in glucose solution before transportation (diluted samples), while the other two were kept undiluted until freezing (undiluted samples). Thus the five treatments were: control, undiluted-3h, diluted-3h, undiluted-6h and diluted-6h. Post-thaw sperm was evaluated for membrane integrity, motility rate and velocities (curvilinear = VCL; average path = VAP; straight line = VSL). Post-thaw membrane integrity did not differ among the five treatments (48-60% intact sperm). Sperm motility rate was similar (P > 0.05) between control (64%) and undiluted samples (60-62%) and higher (P < 0.05) than that in diluted samples (35-45%), regardless the time after collection when freezing took place. Velocities were higher in control and in undiluted-3 h samples (VCL of 254-265 μm/s, VAP of 219-244 μm/s and VSL of 134-147 μm/s) than in diluted samples or samples frozen 6 h after collection. P. lineatus sperm can be transported/shipped to the laboratory without decreasing its suitability for cryopreservation. Sperm should be kept undiluted during storage and be frozen within 3 h.