You cannot freeze the eggs of fish for long periods of time. Recent research in Japan is looking at the use of primordial germ cells that can be frozen. Here is a summary I wrote about some of the research. Really weird science.
SALMON GIVING BIRTH TO TROUT!!! :shocked:
Germ Cell Transplantation in fish:
Surrogate salmon produces trout
Dr. Goro Yoshizaki
Tokyo University of Marine
Sciences and Technology
Tokyo 108-8477, Japan
Executive Summary of Seminar Presentation
April 6th, 2005
Due to the large maintenance costs and space requirements of Japanese bluefin tuna (Thunnus thynnus) aquaculture broodstocks, a research initiative has been started by the Tokyo University of Marine Sciences and Technology. The solution that is being pursued is a novel one. It is the intent of Dr. Yoshizaki and his staff to use horse mackerel (Trachurus japonicus) as surrogates to produce xenogenetic bluefin tuna gametes. This will be accomplished by implanting recipient mackerel larvae with primordial germ cells (PGCs) from tuna donors. If the implantations are successful the progeny of recipient mackerel will be genetically pure bluefin tuna. This would allow aquaculturists to use the easily cultured horse mackerel as a surrogate broodstock for bluefin tuna production.
Dr. Yoshizaki’s group began xenotransplantation technology research with salmonids due to the relative ease with which they can be maintained and bred within the laboratory setting. The first challenge was to develop a technique for identifying live PGCs in the donor animal for transplantation. Yoshizaki’s team identified a gene (Vasa 3’ UTR) that is specific to PGCs, then a commonly used cell marker, GFP (Green Fluorescent Protein), was spliced into the region immediately next to the Vasa gene. This allowed the PGCs expressing the GFP Vasa gene to be easily distinguished under fluorescent microscopy. The use of this marker has also proven advantageous as it is passed on genetically, causing subsequent generations with the gene to be easily identified.
The GFP marked PGCs of rainbow trout (Oncorhynchus mykiss) embryos (35 days post fertilization) were then extracted and injected into the peritoneal cavities of masou salmon (Oncorhynchus masou masou) embryos (45 days post fertilization). To assess the success of the implantations recipient fish gonads were examined 30 days post transfer under fluorescent microscopy and the number of transgenic PGCs per fish were counted.
Milt from recipient masou salmon was then used to fertilize batches of trout eggs. Of the fertilized eggs 0.4% proved to be genetically pure trout. This was the first report of the use of PGC xenotransplantation to produce viable offspring in vertebrates. To increase the number of offspring derived from donor PGC gametes research is currently underway to eliminate the competition from recipient endogenous gametes. Though they have had limited success using gene knockdown techniques, the greatest success has been seen with PGC implantation into sterile triploid recipients. Using this technique all of the trout eggs fertilized with recipient triploid salmon milt have been genetically pure trout.
The current efforts of the research program are to develop an in vitro culture methodology for primordial germ cells. This will allow for the inoculation of many recipients with PGCs derived from just a few donor animals. Yoshizaki stated that the procedure will likely be very similar to current techniques used in the culture of embryonic stem cells in mice.
It is likely that the applications for this new technology will go far beyond the original aquaculture problem. One of the most promising applications is the long term cryogenic preservation of viable genetic material, since cryopreservation of fish ovum and sperm has not been successful thus far. Yoshizaki’s group has already produced viable trout from PGCs that have been frozen for over two years (46.79% survival of embryo’s from frozen PGCs, Vs 83.0% survival in control PGCs). This would allow the rehabilitation, or resuscitation, of a species even after all of the extant individuals are dead. The Tokyo research group has already been contacted by conservation officers in Taiwan who wish to begin exploring the possibility of maintaining a stock Formosan (Oncorhynchus masou formosanum ) land locked salmon PGCs. Formosan are an endemic salmonid of Taiwan and are endangered with a population estimated at less than 1,000 animals. It is also possible that with further development the technique could be used on other vertebrates such as birds and mammals.
One of the greatest challenges faced by groups wanting to use this technology for animal production or conservation is overcoming public opinion opposed to the use of transgenic technologies. Yoshizaki commented that he already receives many emails in protest to his work. What is not obvious, at first, is that the animals produced contain only genetic material from the donors (with the exception of GFP used as a cell marker). In spite of this argument there will still likely be public protest against a technology that may prove extremely useful in a world of dwindling food resources and increasing conservation concerns.
[b] What this means is that they can use another species to produce a fish that has been extinct!!![b]
cool stuff!
GRIFF
duckboy
Cryogenics and Native fish dna stocking
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