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Background:
The growth of intensive aquaculture requires efficient and effective methods to preserve gametes for higher flexibility in broodstock management, genetic improvement programs and preservation of genetic diversity. While methods for cryopreservation of fish spermatozoa are well known, preserving maternally inherited important genetic factors has yet to be achieved. Methods for cryopreservation of yolk-laden fish embryos remain elusive so far, but immature or mature oocytes are a specific challenge. The objective is to develop technologies for cryopreservation of fish oocytes. Multi- disciplinary studies will be performed on the oocyte envelope structure, biological processes during oocyte maturation and hydration, development of in vitro procedures for oocyte maturation, ovulation and fertilization, and on molecular (nucleic acid and protein) markers for indicating oocyte viability prior and after cryopreservation.



Specific workplan:
The aims will be achieved by innovative studies conducted on:

  1. Anticipated biological barriers for cryopreservation including the formation and structure of the vitelline envelope proteins and the process of oocyte hydration of pelagic eggs;
  2. Identification of specific biological markers to monitor oocyte viability after manipulation and /or cryopreservation;
  3. Development of oocyte in vitro incubation procedures to promote oocyte maturation, ovulation and fertilization;
  4. Development of new cryopreservation technologies. Studies on two models (zebrafish and the gilthead seabream) will highlight differences between marine and freshwater species and hydrating and non-hydrating oocytes. The results will improve fish production and increase its efficiency by genome banking of cultured and wild species.


Expected Results And Achievements:
  1. The primary end product will be the development of procedures for successful cryopreservation of fish oocytes maintaining their developmental capabilities.
  2. New and powerful tools for evaluating oocyte and egg characteristics as important diagnostic products for farmed fish and eco-toxicological studies. These will include stage specific molecular markers (in the form of DNA micro or macro-arrays) and protein markers for fish oocytes and egg envelopes, biochemical assays to test the correct enzymatic cleavage of the yolk proteins, and markers to evaluate the buoyancy of pelagic eggs.
  3. Methods for obtaining oocyte maturation and ovulation in vitro that will be extremely helpful in promoting fertilization of naturally non-ovulating oocytes from farmed and wild fish species.
  4. The formation of cryobanks for storage of preserved oocytes for genetic improvement programs, for storage of important maternal genetic traits and easier transfer of genetic material between culture locations at reduced costs and reduced danger of disease transmission. It will provide a unique methodology and greatly contribute to improving the competitiveness of the European aquaculture industry.