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Resource Briefs
A New Way to Preserve Fish
Some fish species, like zebrafish and medaka, have become important models for human disease research, and developmental biology studies. For 15 years, Terrence Tiersch's laboratory at the Louisiana State University Agricultural Center has been preserving fish species by freezing their sperm to facilitate the sharing of these animals among researchers. With the thousands of mutant and transgenic fish lines created around the world, as well as U.S. Customs restrictions on shipping live animals, freezing fish sperm is an easier and more cost-efficient way to maintain and share the lines. Now, Tiersch's group has received funding from NCRR to standardize the freezing process and expand it to a wider scale.
For 15 years, Terrence Tiersch of the Louisiana State University Agricultural Center has been preserving fish species, such as the zebrafish shown here, by freezing their sperm. Currently, Tiersch and colleagues are creating a standardized, high-throughput process that the NCRR-supported Zebrafish International Resource Center and similar facilities can use to maintain fish lines. Photo Courtesy of Terrence R. Tiersch
Currently, there is no standard process for freezing zebrafish or medaka sperm. Individual investigators find their own way, but these methods are often slow, laborious and inconsistent. "People have homemade recipes and borrow technologies from other animal models," said Michael Chang, program director at NCRR.
Indeed, for the past 10 years, Tiersch's group has been using a nearby commercial facility that freezes bull sperm. The facility allows Tiersch access to its equipment, but he has to use the same process for fish that is used for bulls, which is not ideal. Also, being very small, zebrafish and medaka might yield only three microliters — no more than a tiny drop — of sperm sample at most. And even though zebrafish and medaka are similar in size, they are different species, living in different environments, and their sperm behave differently. That means the conditions and requirements for freezing their sperm also differ.
Tiersch's group and three collaborating laboratories are creating a standardized, high-throughput process that stock and resource centers, such as the NCRR-supported Zebrafish International Resource Center, can use to maintain fish lines. The first phase of this work will go beyond freezing alone. The group will identify all the steps on the path, from the state of the fish before sperm collection, to the coding and databases needed to keep track of specimens, to the final distribution of samples to investigators. This work will generate a "first draft" process, which will be fine-tuned in the second phase in collaboration with the resource centers. The final draft will be a process that allows resource centers, which once needed a day to freeze a small number of sperm specimens, to freeze thousands of samples in a shorter period of time.
"We're not just developing a technique or saying things are feasible," Tiersch said. "We're past that. The small scale is already there. We're coming up with the industrial scale."
— Frances McFarland Horne
To Gain Access: The new protocol for freezing zebrafish sperm will be available through resource centers, such as the NCRR-supported Zebrafish International Resource Center (http://zebrafish.org), which stores and maintains more than 1,000 different zebrafish lines. The new protocol will also be available to other resource facilities and research institutions that breed zebrafish and medaka.
