スミソニアン国立動物園のインスタグラム(smithsonianzoo) - 10月26日 00時31分

?‍????For the first time, scientists at the Smithsonian Conservation Biology Institute have successfully frozen and thawed coral larvae. The breakthrough will allow scientists to biobank coral in its early developmental stages. The larvae can be thawed and settled at any time of year, rather than only during the once-yearly spawning period. That will greatly aid conservation efforts to help corals recover from bleaching and adapt to changing oceans. Successful cryopreservation of an embryo requires two important steps. First, scientists must thaw the embryo at a rate faster than it was frozen. Second, they must distribute an antifreeze (or cryoprotectant) solution throughout the embryos to stop the growth of ice crystals in the tissues. Ice behaves like pins in a balloon, rupturing the membrane and causing the embryo to fall apart. Non-mammalian embryos, such as fish, birds and corals, are very large, thus making them extremely difficult to thaw quickly to avoid ice-crystal formation.

The researchers overcame these obstacles by using gold nanorod particles and an infrared laser to warm larvae at millions of degrees per minute. Gold nanorods are tiny cylinders of gold that convert absorbed light (from a laser, for example) into heat. The study’s authors surrounded the coral larvae with cryoprotectant and nanogold particles. The gold particles transferred heat uniformly throughout the larvae when hit with a laser, speeding up the thawing process and, in combination with the cryoprotectant, preventing the formation of lethal ice crystals.

Larvae that underwent the new warming process went on to develop and swim for at least 12 hours after thawing. The team of biologists and engineers are now developing ways to make this process faster so that hundreds of thousands of larvae can be cyropreserved and thawed within a short period of time—moving the cryopreservation and laser-warming process from small to large-scale—to help augment rapid reef restoration efforts. #WeSaveSpecies

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