Students explore the unique traits of organisms that can survive in the extremely cold environment of liquid nitrogen.
--Properties of objects and materials
--Organisms and environments
First, present to students the following three unique organisms.
1. Ozobranchus jantseanus
Recently featured in Popular Science, Ozobranchus jantseanus is a parasitic leech that lives in the freshwaters of East Asia and uses turtles as hosts. It was recently discovered that these tiny buggers can survive in liquid nitrogen (-321°F or -196 °C) for up to 24 hours. The same leeches in the liquid nitrogen experiments also survived temperatures of -130°F for nine months. Some even survived for over two and a half years!
What’s strange is that even though the leeches don’t experience extremely cold temperatures in their typical environment, they don’t need any time to adjust to the cold. These guys can also survive being chilled to -321°F, immediately thawed, quickly chilled again to the extreme temperature and then thawed again to room temperature, without any acclimation time. Scientists were able to repeat this 12 times in about two minutes.
A handful of leeches that survived the experiment lived for over a month in a water bath, eventually dying only of starvation.
Scientists are currently clueless regarding how Ozobranchus jantseanus handles such extremely cold temperatures, but the leeches’ incredible adaptability may have future scientific applications.
2. Chymomyza costata
The Drosophilid fly larva, known as Chymomyza costata, can live submerged in liquid nitrogen (-321°F) while fully hydrated. (The Drosophilidae family of fly has over 4,000 species, which includes common varieties of fruit flies.)
Scientists found that in order to survive, the larvae went into diapause, a process that delays the development of an animal while it’s in a challenging environment. Without acclimation to the cold, the survival rate was 23 percent; a slower acclimation improved the survival rate to 62 percent.
Scientists found that proline, an amino acid, was plentiful within the larvae’s metabolites. Proline increased from 20 to 147 mM while they entered diapause, and larvae with artificially increased proline acclimated much better to the cold.
Enhancing the larvae with proline actually allowed some to survive until adulthood, a percentage that went from 0 to 36 percent.
3. Tardigrade Ramazzottius varieornatus
The invertebrate Tardigrade Ramazzottius varieornatus can enter a state of anhydrobiosis that allows it to survive even the cold of space. While in this state, it is dry and unchanging. This means it could easily survive a long bath in liquid nitrogen.
These little creatures, commonly known as “water bears” and “moss piglets,” maneuver through water with eight stubby, segmented legs that are attached to a chubby, pill-shaped body.
Tardigrades show an extreme tolerance to harsh environments, as do their eggs, scientists have found. Both hydrated and anhydrobiotic eggs hatch even after entering very high and low temperatures and being exposed to helium ions, as well as high vacuum pressure.
Anhydrobiotic eggs have a wide range of temperature resistance when compared to hydrated ones. When anhydrobiotic, more than 70 percent of tested eggs hatched after exposure to the extremely cold temperature of -321°F and the extremely hot temperature of +122°F.
Next, explain to students the Leidenfrost Effect.
While living people can’t survive in liquid nitrogen, did you know that you can dip your hand in a container of liquid nitrogen and remove it unharmed? This is because of something known as the Leidenfrost Effect.
Because nitrogen’s boiling point is the extremely low temperature of -320.4°F (just above the sitting temperature of liquid nitrogen), it hits its Leidenfrost point rather quickly. As soon as the liquid nitrogen makes contact with a mass that’s hotter than itself (say, a person, body of water or surface at room temperature), it rapidly bounces in a layer of insulated vapor as it evaporates. This means it evaporates without ever truly touching the surface with which it’s interacting. This also means that the surrounding oxygen is displaced.
You can see the Leidenfrost Effect in action at an ill-fated party in Mexico, where the organizers added liquid nitrogen to a swimming pool. Watch as the pool party’s guests begin passing out from oxygen deprivation. See the video, as well as an explanation of the science behind what happened, here.
Introducing the discussion to students
Scientists are studying unique creatures that can withstand very cold temperatures. In some cases researchers have discovered the secrets of these creatures' abilities, but in other cases, they remain a mystery. We’re going to learn about a special substance that creates a super-cold environment, then discuss the various methods organisms use to survive being submerged in it. As we’re talking, let’s all think about how scientists’ findings might be applied in the future.
Options for student discussion questions
Extension activity (optional essay)
In what ways can science apply what has been learned about some creatures’ abilities to withstand extremely cold temperatures? Describe some future applications and why they would be important to humans.
Article by Jason Cunningham, EducationWorld Social Media Editor
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