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Sea urchin. (Photo: Stock File)
Sea urchin embryos managed to be frozen for toxicity studies
(SPAIN, 7/29/2014)
A team of researchers from the University of Vigo (UV) has established the first protocol for cryopreservation of sea urchin embryos to be used in the detection of contaminants and in the field of aquaculture.
Cryopreservation makes it possible to maintain biological materials at very low temperatures but its use in the marine environment is still very low in the world.
Marine Ecotoxicology group of the UV uses sea urchin embryos in bioassays to detect the presence of contaminants but one of the constraints being faced is the seasonal variability of the resource.
"Hopefully, we have them for five months a year," explains Estefanía Paredes, whose doctoral thesis focuses on the cryopreservation method developed.
Hence the importance of having a cryobanking cells, adds the expert in Marine Sciences.
Paredes travelled to New Zealand twice and in the Cawthron Institute became acquainted with the cryopreservation techniques used by the group of the expert Serean Adams with the New Zealand mussel (Perna canaliculus) and the oyster (Crassostrea gigas).
The PhD student decided to include both species in her project as well as the Galician mussel (Mytilus galloprovincialis), the newspaper La Opinión reported.
Besides, she travelled to the United States and at the University of Tennessee she worked with Peter Mazur, a pioneer in embryo freezing.
Mazur's lab achieved the first successful cryopreservation of mouse embryos in the 70s.
Paredes explains the cryopreservation of the four species selected is performed in the early stages, namely, during the trochophore larva stage, which appears at 14-16 hours after the embryo is formed.
As with the sea urchin the Spanish group started from scratch, it really did not know how their larvae could be cryopreserved.
According to Paredes, it is a process that is "really elaborate and delicate," in which the most critical elements are the cryoprotectants and freezing rates.
"The cryoprotectants are like the antifreeze from a car and it allows the cells to slowly dehydrate until they freeze without forming ice inside, causing their death," the expert continued explaining.
Since there is also the danger that the antifreeze intoxicates the larvae so its choice requires great care.
As to the freezing rate, this "determines how many degrees per minute the temperature can be made to go down for the dehydration process to take place under suitable conditions."
When the embryos are frozen, they are submerged in liquid nitrogen at almost 200 °C. If the process has been successful, when the embryos are thawed, they are reactivated gradually.
The researcher set a portable cryo-chamber that allowed her to perform her studies in the laboratories of the campus and the Marine Science Station in Toralla (ECIMAT).
The biologist compared the results of the bioassays performed with fresh larvae with those that were frozen, and concluded that the frozen ones can offer the same reliability in the detection of organic pollutants and heavy metals in seawater.
By Analia Murias
editorial@seafood.media
www.seafood.media
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