Leech has a remarkably high tolerance to freezing and thawing

Mar 03, 2014 by Aaron L. Gronstal
Stereoscopic micrograph of Ozobranchus jantseanus (dorsal view). O. jantseanus is a parasitic leech of freshwater turtles. Credit: Suzuki et al. 2014

Imagine you're a leech, happily making a living on a turtle in some quiet, freshwater pond. What do you do when winter comes and temperatures in your warm little habitat begins to dip below freezing?

In a recent study, a team of researchers discovered that the leech, Ozobranchus jantseanus, has a remarkably high tolerance to freezing and thawing. Scientists once thought that it would be difficult for organisms to survive at temperatures below freezing because the water inside cells and tissues forms ice crystals, and this can ultimately damage the cells beyond repair.

In the new study, O. jantseanus survived after being stored for 24 hours in at temperatures of -196°C. The leech also recovered after being stored for 32 months at -90°C, and repeated freeze-thaw cycles at temperatures that fluctuated between from 20°C to −100°C.

O. jantseanus has shown incredible adaptability, and its unique mechanisms for dealing with the cold allows it to survive in a much wider range of temperatures than previously documented in other organisms.

According to the paper by Suzuki et al., "All of the individuals had been active before initiating the experiments, indicating that this cryoresistance ability is always present in O. jantseanus."

Studying how life adapts to adverse conditions, such as high and low environments, is an important aspect of astrobiology research. If life survives on planets and moons like Mars and Europa, organisms will have to cope with environmental conditions that are often far more extreme than those found in habitats on Earth. Cryobiosis is a term used to describe adaptations or tolerance of , and could be an important survival strategy for potential life in cold environments, such as beneath the icy shell of Jupiter's moon Europa.

Explore further: Many insect pests have survival strategies for cold weather

More information: Suzuki D, Miyamoto T, Kikawada T, Watanabe M, Suzuki T (2014) "A Leech Capable of Surviving Exposure to Extremely Low Temperatures." PLoS ONE 9(1): e86807. DOI: 10.1371/journal.pone.0086807

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Tangent2
not rated yet Mar 03, 2014
This summary article is quite lacking in the underlying mechanism that these leeches employ to survive cryo temperatures. I don't know why the author didn't bother adding this to the article, which I found on the PLoS One article:

Indeed, trehalose or glycerol, which are typical cryoprotectants, were not detected before or after freezing (data not shown), implying that the low-temperature tolerance observed in the leeches of this study is not attributable to these saccharides; instead, it appears that that the leeches may be capable of tolerating physiological water freezing in their tissues. Anhydrobiotic organisms can withstand low temperatures indefinitely by becoming dehydrated, but cryobiotic organisms do not employ desiccation [17]. Indeed, the finding that O. jantseanus cannot survive dry conditions, for example a keeping of the leech at a petri dish without water in 24 hours at room temperature, implies that this leech species is a cryobiotic organism.

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