Les technologies du froid au service de la préservation de la biodiversité (en anglais)
According to the recent Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) on Biodiversity and Ecosystem Services1, at least a million species are at risk of extinction because of human actions. The abundance of native species in most major land habitats has fallen by a fifth since 1900.
In particular, nearly a third of corals around the world and more than a third of marine mammals are also threatened. In this field, refrigeration technologies may help maintain biodiversity through the cryopreservation of genetic resources. Coral reefs, the lush habitats that are home to around one quarter of the ocean’s species, are dying off at an alarming rate. The United Nations projects that, if ocean temperatures rise as forecasted, none of the 29 reefs listed as UNESCO world heritage sites will still house functional ecosystems by the year 21002.
Using an antifreeze solution laden with gold particles and quick-thaw lasers, a Hawaii-based team has cryogenically frozen and successfully thawed coral larvae for the first time.
Despite past successes with ultra-low temperature storage of coral sperm to conserve genetic diversity, cryopreservation of larvae has remained elusive due to their large volume, membrane complexity, and sensitivity to chilling injury. In an article published in Nature3, the researchers show for the first time that coral larvae can survive cryopreservation and resume swimming after warming. Vitrification in a cryoprotectant solution followed by warming at a rate of approximately 4,500,000°C/min with an infrared laser resulted in up to 43% survival of Fungia scutaria larvae on day 2 post-fertilization. Surviving larvae swam and continued to develop for at least 12?hours after laser-warming. This technology will enable biobanking of coral larvae to secure biodiversity, and, if managed in a high-throughput manner where millions of larvae in a species are frozen at one time, it could become an invaluable research and conservation tool to help restore and diversify wild reef habitats.
In another domain, refrigeration is used by Washington State University researchers to help fight the parasitic varroa mite, one of the suspected causes of bee colony collapse4.
Varroa mites are pests that weaken bees’ immune systems, transmit viruses and siphon off nutrients. A significant mite infestation will lead to the death of a honeybee colony, usually in the late autumn through early spring. They’re a huge factor in colony collapse around the world. Various treatments against the mites are available but, they only kill varroa on adult bees and are generally only effective for three days. Bees do not truly hibernate, but they do change their behaviour in winter. Queens stop laying eggs, so no new “brood” is created at that time.
Last August, WSU researchers put 200 honeybee colonies into refrigerated storage. This is a time when bees are still active, but have finished making honey for the season, and there are no crops that require pollination. It is also when beekeepers normally do a round of mite treatments. By placing colonies in refrigerators, the queen stops laying new eggs, which stops the production of brood. When the bees come out of refrigeration, there is no “capped brood”. At that point, the WSU team applied a varroa treatment on the adult bees. The initial results were said to have been overwhelmingly positive. Researchers found an average of five mites per 100 bees on the control colonies (not refrigerated) one month after the normal three-cycle mite treatment. The refrigerated colonies had an average of 0.2 mites per 100 bees one month after the single mite treatment. These initial results need confirmation but, if this works, it could be a major and environmentally sound victory in the great varroa mite battle that beekeepers have been waging for decades.