30th January 2014 Leech can survive being frozen for long periods Japanese researchers have discovered a species of leech able to survive for 24 hours at -196°C (-321°F) and for 32 months at -90°C (-130°F). This finding could provide insights into cryopreservation for humans. It also increases the chances of life elsewhere in the universe.
Pictured above is Ozobranchus jantseanus, a parasitic leech that feeds on the blood of freshwater turtles in East Asia. These creatures typically reach up to 15 mm (0.6") in length, attaching themselves externally and relying on their hosts for all of their life stages, from egg to adult. A team from Tokyo University of Marine Science and Technology – working on a separate project – had pulled a frozen, dead turtle out of storage, when they noticed several of these parasites clinging to the animal. The leeches appeared to be still alive, wriggling as they began to warm up. The researchers knew they had found something highly unusual, as it was rare for any organism to withstand such low temperatures. A new study was undertaken to investigate this further and to determine the full extent of their cold tolerance. Prior to the experiment, only two other animals were known to survive in liquid nitrogen – a microscopic invertebrate known as the waterbear and the larvae of a drosophilid fly – with maximum recorded submersion times of 15 minutes and one hour, respectively.
Cryoexposure tests were conducted on seven different species of leech, at -90°C and -196°C, for a period of 24 hours. Ozobranchus jantseanus was the only one to survive both temperatures. In fact, it could withstand multiple freezes and repeated freeze-thaw cycles, without needing time to acclimatise. An even more amazing discovery was to follow, however. Every single leech from this species placed at -90°C (-130°F) survived at least nine months, with some lasting in storage for 32 months, or more than 2.5 years. This is colder than the average temperature on Mars. At present, it is unknown how these creatures are managing to cope with such an extreme environment. "It is likely that this cryotolerant ability has arisen in response to some as yet unclarified adaptation," the researchers state. "It is hoped that these findings will contribute to the development of new cryopreservation methods that do not require additives, and also to the resuscitation of organisms that have been frozen underground in permafrost areas, on Antarctica, and possibly on other planets." Their work is published in PLOS ONE.
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