TardigradaTardigrada

KIM, WOOSOOKIM, WOOSOO

BSBIO2ABSBIO2A

Phylum: TardigradaPhylum: TardigradaWater BearsWater Bears

First discovered in 1773First discovered in 1773 800 spp800 spp 0.1-0.5mm in length0.1-0.5mm in length WidespreadWidespread Live in semi aquatic habitats, Live in semi aquatic habitats,

water filmwater film Cryptobiotic, some are Cryptobiotic, some are

cyclomorphiccyclomorphic Temp range from +149C to -Temp range from +149C to -

272C, withstand high vacuum, 272C, withstand high vacuum, high UV, long periods without Ohigh UV, long periods without O2 2

Dessication for > 120 years: back Dessication for > 120 years: back to life in hoursto life in hours

CharacteristicCharacteristic 1)Bilaterally symmetrical. 1)Bilaterally symmetrical.

2)Body has more than two cell layers, tissues and organs. 2)Body has more than two cell layers, tissues and organs.

3)Body cavity is partially a coelom. 3)Body cavity is partially a coelom.

4)Most possesses a through straight gut with an anus. 4)Most possesses a through straight gut with an anus.

5)Body monomeric. 5)Body monomeric.

6)Body possesses 4 pairs of unjointed claw bearing legs. 6)Body possesses 4 pairs of unjointed claw bearing legs.

7)Body possesses a fixed number of cells (eutelic). 7)Body possesses a fixed number of cells (eutelic).

8)Has no circulatory or respiratory system. 8)Has no circulatory or respiratory system.

9)Primitive excretory organs in some species. 9)Primitive excretory organs in some species.

10)Reproduction normally sexual and 10)Reproduction normally sexual and gonochoristic, but can be parthenogenetic. gonochoristic, but can be parthenogenetic.

11)Feed on a plants or small animals. 11)Feed on a plants or small animals.

12)All live in aquatic or damp places, 12)All live in aquatic or damp places, normally associated with vegetation. normally associated with vegetation.

ClassficationClassfication

Kingdom: Kingdom: AnimaliaAnimalia Superphylum: Superphylum: EcdysozoaEcdysozoa (unranked): (unranked): PanarthropodaPanarthropoda Phylum: Phylum: TardigradaTardigrada

PhysiologyPhysiology

Tardigrades have been known to withstand the following Tardigrades have been known to withstand the following extremes while in this state:extremes while in this state:

TemperatureTemperature – tardigrades can survive being heated for a few – tardigrades can survive being heated for a few minutes to 151 °C.minutes to 151 °C.

PressurePressure – they can withstand the extremely low pressure of a – they can withstand the extremely low pressure of a vacuumvacuum and also very high pressures, more than 1,200 times and also very high pressures, more than 1,200 times atmospheric pressureatmospheric pressure. .

DehydrationDehydration – tardigrades have been shown to survive nearly – tardigrades have been shown to survive nearly 10 years in a dry state. When encountered by extremely low 10 years in a dry state. When encountered by extremely low temperatures, their body composition goes from 85% water to temperatures, their body composition goes from 85% water to only 3%. As water expands upon freezing.only 3%. As water expands upon freezing.

RadiationRadiation – tardigrades can withstand median lethal – tardigrades can withstand median lethal doses of 5,000 doses of 5,000 GyGy (of gamma-rays) and 6,200 Gy (of (of gamma-rays) and 6,200 Gy (of heavy ions) in hydrated animals (5 to 10 Gy could be heavy ions) in hydrated animals (5 to 10 Gy could be fatal to a human). fatal to a human).

Environmental Environmental toxinstoxins – tardigrades can undergo – tardigrades can undergo chemobiosis—a chemobiosis—a cryptobioticcryptobiotic response to high levels response to high levels of environmental toxins. However, these laboratory of environmental toxins. However, these laboratory results have yet to be verified.results have yet to be verified.

Metabolism Metabolism

Tardigrades exchange gases through their cuticle. The Tardigrades exchange gases through their cuticle. The substances taken up by diffusion are often stored in substances taken up by diffusion are often stored in storage cells that are found in the body fluid. storage cells that are found in the body fluid.

Tardigrades do not have a circulatory system; the Tardigrades do not have a circulatory system; the fluids are moved around the body cavity by the fluids are moved around the body cavity by the movement of the animal. movement of the animal.

Osmoregulation is accomplished by the Malpighian Osmoregulation is accomplished by the Malpighian tubules located at the midgut-hindgut junction. tubules located at the midgut-hindgut junction.

Ecology Ecology

Tardigrades occur in Tardigrades occur in marinemarine, freshwater and , freshwater and terrestrial habitats worldwide. terrestrial habitats worldwide.

They live in a wide variety of habitats They live in a wide variety of habitats including including soilssoils, leaf litter, moss, , leaf litter, moss, lichenslichens, , flowering plants, algae and even in hot flowering plants, algae and even in hot springs. Some tardigrades live on the legs of springs. Some tardigrades live on the legs of isopods, on the gills of mussels or as isopods, on the gills of mussels or as parasitesparasites on the epidermis of barnacles or holothurians. on the epidermis of barnacles or holothurians.

Idiosyncratic Inverts Idiosyncratic Inverts

When environmental conditions start to deteriorate, tardigrades When environmental conditions start to deteriorate, tardigrades enter a latent state until conditions improve.enter a latent state until conditions improve.

Encystment Encystment - A latent state in which resistant cysts are - A latent state in which resistant cysts are

produced. produced. FreshwaterFreshwater tardigrades in permanent water tardigrades in permanent water habitatshabitats enter this state when environmental conditions deteriorate. enter this state when environmental conditions deteriorate. These cysts can't withstand high temperatures, but can survive These cysts can't withstand high temperatures, but can survive a year without food. a year without food.

Anoxybiosis Anoxybiosis - A latent state that is induced by low oxygen - A latent state that is induced by low oxygen concentrations in the surrounding water. In this state concentrations in the surrounding water. In this state tardigrades become immobile, transparent, rigid and extendedtardigrades become immobile, transparent, rigid and extended

Cryobiosis Cryobiosis - If cooled gradually, tardigrades form a - If cooled gradually, tardigrades form a cold-resistant tuns which allows the animal to survive cold-resistant tuns which allows the animal to survive being frozen. being frozen.

Osmobiosis Osmobiosis - Tun production induced by elevated - Tun production induced by elevated osmotic pressure and decreased water availability. osmotic pressure and decreased water availability. For example, a freshwater tardigrade placed in For example, a freshwater tardigrade placed in salt watersalt water will form a tun. will form a tun.

Anhydrobiosis Anhydrobiosis - Tun production in - Tun production in terrestrialterrestrial tardigrades that is induced by tardigrades that is induced by evaporativeevaporative water loss. water loss. If the tardigrade dehydrates too quickly, it will not If the tardigrade dehydrates too quickly, it will not survive. survive.

Reproduction Reproduction

Most tardigrades reproduce parthenogenetically, Most tardigrades reproduce parthenogenetically, but a few reproduce sexually.but a few reproduce sexually.

Some species are simultaneous hermaphrodites, Some species are simultaneous hermaphrodites, which are able to fertilize themselves, but which are able to fertilize themselves, but sequential hermaphroditism is more common. sequential hermaphroditism is more common.

Both males and females have only one gonad, and Both males and females have only one gonad, and it lies dorsal to the intestine. it lies dorsal to the intestine.

Species of TardigradaSpecies of Tardigrada HypsibiusHypsibius is a genus of water bearis a genus of water bear or or moss moss

pigletpiglet, a , a tardigradetardigrade in the class in the class EutardigradaEutardigrada..

Kingdom: Kingdom: AnimaliaAnimalia Phylum: Phylum: TardigradaTardigrada Class: Class: EutardigradaEutardigrada Order: Order: ParachaelaParachaela Family: Family: HypsibiidaeHypsibiidae Subfamily: Subfamily: HypsibiinaeHypsibiinae Genus: Genus: HypsibiusHypsibius

Echiniscoides sigimundeEchiniscoides sigimunde

Water bearWater bear Kingdom - Animalia Kingdom - Animalia Phylum - Tardigrada Phylum - Tardigrada Class - Heterotardigrada Class - Heterotardigrada Order - Echiniscoidea Order - Echiniscoidea Family - Echiniscoididae Family - Echiniscoididae Genus - Echiniscoides Genus - Echiniscoides