Research articleEffect of postthaw storage time and sperm-to-egg ratio on fertility of cryopreserved brook trout sperm
Introduction
The brook trout (Salvelinus fontinalis; Mitchill) of the family salmonidae is important commercially, recreationally, and ecologically in Europe. It is of interest in aquaculture because it is almost completely resistant to the viral hemorrhagic septicemia virus [1] and can easily be subjected to genome manipulation. The use of cryopreserved sperm improves the genetic characteristics of species, ensures the long-term sustainability of improved lines, reduces risks involved with the natural reproductive methods of animals, and improves efficiency in production practices. The cryopreservation procedure of brook trout semen has been evaluated [2], [3]. This method secures good fertilization rates, but a high sperm-to-egg ratio (7–9 × 105) is necessary. Because prolonged handling time of thawed semen is of practical interest for the better organization of hatchery work, it is worth to examine how long postthaw brook trout semen can be stored without changes in sperm motility parameters. Furthermore, it is of interest if the application of lower than previously published sperm-to-egg ratios for the brook trout fertilization [2], [3] will secure high fertilizing ability.
The aim of this study was to test the influence of postthaw storage time on sperm motility parameters of brook trout. Furthermore, we examined the effect of sperm-to-egg ratios of 300,000:1 and 600,000:1 on sperm motility parameters and fertilizing capacity of postthaw, cryopreserved, brook trout sperm.
Section snippets
Brood stock and gamete collection
This study was approved by the Animal Experiments Local Committee in Olsztyn, Poland (no. 114/2011).
Males (n = 9; more than 2 years of age; weight, 550 ± 143 g; total length, 31.6 ± 3.2 cm) and females (n = 2; more than 3 years of age; weight, 1050 ± 211 g; total length, 38.2 ± 3.8 cm) were born and raised in the Rutki Salmonid Research Laboratory (54.331240N; 18,341246E) at the Institute of Inland Fisheries in Olsztyn. The fish were stocked in concrete ponds (150 m3) supplied with water from
Results
The percentage of postthawed sperm motility, VSL, and VAP was not affected by 60 minutes of storage, whereas a decrease in VCL and ALH and an increase in LIN were observed in cryopreserved semen (Fig. 1). The cryopreservation procedure resulted in very high postthaw sperm motility of about 57%. The percentage of fresh sperm motility decreased by 34% after cryopreservation. Similarly, a significant decline in VCL and ALH values was found for cryopreserved semen. At the same time, VSL, VAP, and
Discussion
It had been assumed that thawed semen must be used immediately for fertilization and 30-second sperm storage after thawing significantly reduces the fertilization rate [2], [11]. In this study, we demonstrated that the cryopreserved sperm of brook trout can be stored for 60 minutes without a loss of percentage of sperm motility, VSL, and VAP. To our knowledge, this is the first report concerning the examination of the effect of the storage period on the postthaw sperm motility parameters of
Acknowledgments
This work was supported by Iuventus grant IP2011 0390 71 from Polish Ministry of Higher Education, funds of the National Science Centre granted on research project number 2011/01/D/NZ9/03738, and funds appropriated to the Institute of Animal Reproduction and Food Research, Polish Academy of Sciences. The support of COST Action FA1205 AQUAGAMETE “Assessing and improving the quality of aquatic animal gametes to enhance aquatic resources—The need to harmonize and standardize evolving
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