The Water Bear

1. 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: (over800!) 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:0.3-0.5mm(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 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!