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Weird Science: Cryptobiosis

NGSS Crosscutting Concepts:

All living organisms use enzymes to complete metabolism, converting chemical compounds into the usable energy needed to survive. However, some organisms are capable of suspending their metabolism.

 

Cryptobiosis is a state of extreme inactivity in response to adverse environmental conditions. In the cryptobiotic state, all metabolic procedures stop, preventing reproduction, development, and repair. In cryptobiosis, an organism can live almost indefinitely while it waits for environmental conditions to become better.

 

The most common type of cryptobiosis is desiccation or drying out. Examples of organisms with cryptobiotic desiccation include nematodes (roundworms), brine shrimp, the majority of plant seeds, the resurrection plant Craterostigma plantagineum, and many microorganisms, including yeast.

 

Brine Shrimp

Brine shrimp are aquatic crustaceans that live in salty lakes worldwide (SF Fig. 1.1 A; genus Artemia). They are often sold in pet stores marketed as “Sea-Monkeys.” Brine shrimp have the ability to produce dormant eggs, known as cysts, when conditions are unfavorable (e.g., low oxygen levels or high salinity). Cysts are metabolically inactive and can survive dry, oxygen-free conditions, even at temperatures below freezing. Cysts can also survive boiling.

 

Yeast

Active dry yeast is a form of baker’s yeast (SF Fig. 1.1 B; species Saccharomyces cerevisiae, a fungi) that is commonly used as a leavening agent in baking. It consists of live yeast cells encapsulated in a thick jacket of dry, dead cells with some growth medium. Under most conditions, active dry yeast must first be rehydrated (this appears in recipes as “allow dough to rise”). Yeast can be stored at room temperature for a year, or kept in the refrigerator or freezer for more than a decade.

 

Tardigrades

Tardigrades (also known as water bears or moss piglets) are microscopic aquatic animals (SF Fig. 1.1 C). Fully-grown adult tardigrades have eight legs and are about 0.5 millimeter long. To date, more than 1000 species of tardigrades have been discovered from all over the world including high on Himalayan mountain peaks, in the abyssal deep sea, in tropical rainforests, and in Antarctica. They are able to suspend their metabolism and fall into cryptobiosis for almost 10 years. This adaptation allows tardigrades to survive extreme conditions of temperature, pressure, dehydration, and even radiation.

 

<p><strong>SF Fig. 1.1.</strong> (<strong>A</strong>) <em>Artemia</em> sp. brine shrimp</p><br />
<p><strong>SF Fig. 1.1.</strong> (<strong>B</strong>) <em>Saccharomyces cerevisiae</em> baker’s yeast. Numbered marks are 11 micrometers apart.</p> <p><strong>SF Fig. 1.1.</strong> (<strong>C</strong>) Tardigrade</p><br />


 

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.