The strangest aspects of the human experience

Tardigrades

03/10/2022

So what is a tardigrade?

  • Most people have heard of tardigrades because they can "survive in space"

  • Also weirdly popular in pop culture in the last 6 years? Shown on "Kipo and the Age of the Wonderbeasts" as a character

Tardigrades AKA moss piglets AKA water bears are animals. They belong to their own phyla, Tardigrada. There are about 1300 species. Their name is from the Latin for "slow walker" or "slow stepper". They got the nickname "water bear" from Johann August Ephraim Goeze who discovered them in 1773 called them kleiner Wasserbär (little water bear) and they're often called Bärtierchen or "little bear-animal". The bear comes from their gait which is similar to a bears.

Tardigrades are translucent, have 4 segments, each with two legs. They have little claws on each leg. They have funny little faces (VERY CUTE) with a suction cup-looking mouth. The average tardigrade is about 0.05mm long (half the size of a 12 point font period), with the largest species being 1.2 mm.

Tardigrades produces via parthenogenesis as well as sexually. Some tardigrades have external fertilization and some have internal fertilization - all lay eggs. Eggs typically hatch after 14 days.

Episode: File 0063: Planet Montauk: Water Bears and Lost Anime Pt. 2

Release Date: March 11 2022

Researched and presented by Courtney

Tardigrade - Kipo and the Age of the Wonderbeasts
Tardigrade - Kipo and the Age of the Wonderbeasts

Most plant-eating tardigrades feed by piercing individual plant cells with their stylets (spear-like structures near the mouth) and then sucking out the cell contents. Some tardigrades are predators and eat rotifers (a microscopic invertebrate)

They are prey to amoebas, nematodes, and other tardigrades.

Tardigrades are found in every biosphere on earth: deserts, tundra, freshwater, salt water, ice, snow, soil, leaf litter, hot springs, mountain tops (Himalayas) ... anywhere as long as they get some moisture. They are often found on moss and lichen.

SO HOW DO THEY SURVIVE SPACE??!?!?!

Here's the thing; tardigrades aren't living/thriving in a vacuum. They're in a suspended state called the "tun" state. While in this state, they curl up in a little ball or withdrawing into their cuticle (outer shell) and their metabolism goes to 0.1% of their normal rate. This tun state allows them to survive

  • Extreme temperatures
  • 30 years at −20 °C (−4 °F)
  • A few days at −200 °C (−328 °F; 73 K)
  • A few minutes at −272 °C (−458 °F; 1 K)
  • New studies do show that most tardigrades will die at 48 hours at 37.1 °C (98.8 °F) if they're not acclimatized to high heat.
  • Pressure - they can withstand the extremely low pressure of a vacuum and also very high pressures, more than 1,200 times atmospheric pressure. Some species can also withstand pressure of 6,000 atmospheres, which is nearly six times the pressure of water in the deepest ocean trench, the Mariana Trench. Tardigrades can survive altitudes of over 19,600 feet (6,000 meters) and to depths of over 15,000 feet (4,700 m) below the surface
  • Dehydration - the longest that living tardigrades have been shown to survive in a dry state is nearly 10 years, although there is one report of leg movement, not generally considered "survival", in a 120-year-old specimen from dried moss. When exposed to extremely low temperatures, their body composition goes from 85% water to only 3%. Because water expands upon freezing, dehydration ensures the tardigrades' tissues are not ruptured by the expansion of freezing ice.

  • Radiation - tardigrades can withstand 1,000 times more radiation than other animals, median lethal doses of 5,000 Gy (of gamma rays) and 6,200 Gy (of heavy ions) in hydrated animals (5 to 10 Gy could be fatal to a human). The only explanation found in earlier experiments for this ability was that their lowered water state provides fewer reactants for ionizing radiation. However, subsequent research found that tardigrades, when hydrated, still remain highly resistant to shortwave UV radiation in comparison to other animals, and that one factor for this is their efficient ability to repair damage to their DNA resulting from that exposure.

  • Irradiation of tardigrade eggs collected directly from a natural substrate (moss) showed a clear dose-related response, with a steep decline in hatchability at doses up to 4 kGy, above which no eggs hatched. The eggs were more tolerant to radiation late in development. No eggs irradiated at the early developmental stage hatched, and only one egg at middle stage hatched, while eggs irradiated in the late stage hatched at a rate indistinguishable from controls.

  • Environmental toxins - tardigrades are reported to undergo chemobiosis, a cryptobiotic response to high levels of environmental toxins. However, as of 2001, these laboratory results have yet to be verified.

COCKROACHES WHO?

So really they are the only animal to be revived after being exposed to space. There was a mission in 2019 that sent some tardigrade tuns to the moon but the rocket crashed and they probably died.  

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