Avaliação de técnicas de criopreservação de sêmen do camarão branco, Litopenaeus schmitti (Crustacea, Dendrobranchiata, Penaeidae).

Abstract

The white shrimp L. schmitti is regarded as one of the most promising species for aquaculture in Brazil. This study was to evaluate techniques for sperm cryopreservation of L. schmitti, using two cryoprotectants, glycerol and DMSO and the influence of time of freezing on sperm viability. The experiment was divided into two phases where, in the first phase experiment was conducted on a randomly designed with two cryoprotectants (Glycerol and DMSO), two concentrations (5 and 10%), and two balance periods (10 and 30 minutes) with 4 replicates. In the second phase, the experiment was conducted in completely randomized design with a split plot design, evaluating two dilutions of glycerol (5 and 10%) in three periods of cryopreservation (24 hours, 15 and 30 days), and each treatment with 6 replicates. The results of the toxicity test to cryoprotective agents showed no significant difference between treatments in both Glycerol and DMSO concentrations, nor between the two balance periods tested, getting rates of sperm viability up to 97.42% after exposure to them. According to the results of the first stage and other favorable characteristics, the Glycerol was selected as cryoprotectant agent for the second phase. The results of the second phase indicated no significant difference between the concentrations of Glycerol at 5 and 10%, with no effect on sperm viability over the 30 days of cryopreservation. However, there was significant difference in survival over time for maintenance in nitrogen, where we observed a survival average of 50.7% at 24 hours, 42.78% after 15 days and 16.26% after 30 days of cryopreservation. Therefore, the cryoprotectants Glycerol and DMSO at 5 and 10% in exposure times of 10 and 30 minutes, not proved to be toxic to sperm of Litopenaeus schmitti. However, the storage time of the spermatic mass significantly reduced the viability of sperm between the 15th and 30th day of cryopreservation, in liquid nitrogen. This result is due to the oscillations observed in the cooling rate (0,5oC.min-1), which probably influenced the high mortality of sperm cells, observed in this phase. Thus, this result suggests the need to repeat this second phase, and the use of another gradual freezing equipment for comparison.