1. An unknown animal you’ve passed before. . . By Nick Yeh
The Water Bear
An unknown animal you’ve passed before. . .
By Nick Yeh

2. Classification Kingdom: Animalia Phylum: Tardigrada
Class: Heterotardigrada
Order: Echiniscoidea
Family: Echinisidae
Genus: Echiniscis
Species: (over 800!)
Scientific Name: Tardigrada
Common Name: Water Bear

3. Description Multicellular invertebrates Microscopic bear w/claws
(moves like a bear)
Have brain, legs, nerves, mouth, & eyes
Smaller by a factor of 100 compared to humans
Size: mm(200 microns)
Weight: not available

4. Description…continued
Have precise muscle control like larger animals
Eat white cushion moss, predatory nematode, rotifer, and green algae
Nematodes eat water bears
Break down lichens, mosses, and water
Harmless to humans!

5. Cryptobiosis Death-like state where they suspend their metabolism
Other organisms usually die when they do this!
Their metabolism decreases to less than 0.01% of normal and the water content in their bodies decreases to less than 1%
Naturally, water bears can stay in this state for 12 years, but in labs they have lived up to 100 years and still showed signs of life. Theoretically, if they are frozen in this state, they can live forever!

6. Forms of Cryptobiosis
There are four forms of cryptobiosis: anhydrobisis, cryobiosis, osmobiosis, and anoxybiosis
Anhydrobiosis-initiated by desiccation (studied the most)
used in limno-terrestrial habitats (like mosses)
involves complete water loss and a tun formation which leaves the water bear folded and constricted
uses metabolism and trehelose, a protective sugar
revival time depends on the time spent in anhydrobiosis
Cryobiosis-initiated by temperatures below 0C (32F)
orders freezing of body water
Osmobiosis-initiated by need for water
Anoxybiosis-initiated by need for oxygen

7. Super Water Bear When in cryptobiosis they are… Nearly indestructible!
Able to withstand 150C (302F) and almost absolute zero (-272.8C) or (-459F) which has no free molecular vibration and where no organism’s metabolism can survive
Resistant to x-rays of 570,000 Roentgens whereas 500 Roentgens are fatal to us
Resistant to vacuums like outer space, a few noxious chemicals, boiling alcohol, and pressures that are six times greater than the bottom of the deepest ocean

8. Reproduction Reproduce sexually Period: n/a
Produce anywhere from 1-30 eggs at a time
Frequency of birth: n/a
Egg size: 100 microns

9. Where Are they? Can live almost anywhere!
Prefer to live in white cushion moss, green algae, British soldiers (a type of lichen), and common greenshield (type of lichen).
You can see water bears for yourself…
soak moss or lichen sample in water for a few hours and shake or squeeze to release any water bears in sample
examine water released under microscope with at least 30x power (you can also use a hand lens)

10. Other Details Closest Relations… Like arachnids because of eight legs
Similar characteristics to nematodes & crustaceans
Life Expectancy…
No exact life expectancy
Minimum in a culture dish is one year
The desiccation period can last seven years

11. Water Bear Clip

12. References Thank You! Searched “water bear” and found these websites
Thank You!