Transcript The Water Bear

The Water Bear
An unknown animal you’ve passed before. . .
By Nick Yeh
Classification
Kingdom: Animalia
Phylum: Tardigrada
Class: Heterotardigrada
Order: Echiniscoidea
Family: Echinisidae
Genus: Echiniscis
Species: (over 800!)
Scientific Name: Tardigrada
Common Name: Water Bear
Description
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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:0.3-0.5mm(200 microns)
Weight: not available
Description…continued
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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!
Cryptobiosis
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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!
Forms of Cryptobiosis
There are four forms of cryptobiosis: anhydrobisis, cryobiosis, osmobiosis, and
anoxybiosis
 Anhydrobiosis-initiated by desiccation (studied the most)
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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
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revival time depends on the time spent in anhydrobiosis
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Cryobiosis-initiated by temperatures below 0C (32F)
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orders freezing of body water
Osmobiosis-initiated by need for water
Anoxybiosis-initiated by need for oxygen
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
Reproduction
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Reproduce sexually
Period: n/a
Produce anywhere
from 1-30 eggs at a
time
Frequency of birth: n/a
Egg size: 100 microns
Where Are they?
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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…
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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)
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
Water Bear Clip
References
Searched “water bear” and found these websites
www.museums.org.za/bio/tardigrades/index.htm
www.everything2.com/index.pl?node_id=358861
www.baertierchen.de/main_engl.html
www.fcps.k12.va.us/StratfordLandingES/Ecology/mpages/water_bear.htm
Thank You!