Title page for ETD etd-08252011-163658


Type of Document Dissertation
Author Cuevas Uribe, Rafael
Author's Email Address rcueva4@lsu.edu
URN etd-08252011-163658
Title A General Approach for Vitrification of Fish Sperm
Degree Doctor of Philosophy (Ph.D.)
Department Renewable Natural Resources
Advisory Committee
Advisor Name Title
Tiersch,Terrence R. Committee Chair
Green, Christopher C. Committee Member
Leibo, Stanley P. Committee Member
Romaire, Robert P. Committee Member
Walter, Ronald B. Committee Member
Bargu Ates, Sibel Dean's Representative
Keywords
  • germplasm
  • cryopreservation
  • conservation
Date of Defense 2011-08-05
Availability unrestricted
Abstract
The goal of this project was to develop streamlined protocols that could be integrated into a standardized approach for vitrification of germplasm for all aquatic species. Vitrification (freezing by formation of “glass” rather than crystalline ice) is simple, fast, inexpensive, can be potentially used to preserve samples in the field, and offers new options for germplasm management especially appropriate for small fishes. Sperm were studied from freshwater fish (channel catfish Ictalurus punctatus), viviparous freshwater fish (green swordtail Xiphophorus hellerii), and marine fishes (spotted seatrout Cynoscion nebulosus, red snapper Lutjanus campechanus, red drum Sciaenops ocellatus, and southern flounder Paralichthys lethostigma). To reduce toxicity, combinations of cryoprotectants at reduced concentrations with incorporation of trehalose and polymers were used to enhance glass formation. For freezing, samples were suspended on 10-µL polystyrene loops and plunged into liquid nitrogen. Thawing was done at 24şC using Hanks’ balanced salt solution at 300 mOsmol/kg for freshwater species, and seawater at 1,020 mOsmol/kg for marine species. Quality after vitrification was evaluated by sperm motility, membrane integrity and when possible fertility. Post-thaw motility of sperm in marine fishes was higher (as high as 70%) than in freshwater fishes (as high as 20%). The percentage of membrane-intact sperm for marine fishes was ~20% except for southern flounder (11%). For freshwater fishes, the percentage of membrane-intact sperm for swordtail was low (<12%) compared to channel catfish (~50%). Adaptations by marine fish to high osmotic pressures could explain the survival in the high cryoprotectant concentrations (40 – 60%) required for vitrification. This research yielded the first successful vitrification of sperm in these fishes and production of offspring from vitrified sperm in channel catfish, green swordtail, and southern flounder. Sperm vitrification offers an alternative approach to conventional cryopreservation for conservation of valuable genetic lineages, such as endangered species, model strains used in research, and improved farmed strains. Furthermore, sperm vitrification could be used to transport cryopreserved sperm from the field to the laboratory to expand genetic resources available for germplasm repositories. This technique could be utilized to reconstitute genetic lines, and as a new option for conservation biology in imperiled aquatic species.
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