Tardigrades

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Tardigrades

Tardigrades

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Introduction

Tardigrades = microscopic, eight-legged aquatic animals.
Also called “water bears” or “moss piglets”.
Existed for ~600 million years, predating dinosaurs.
Survived all five major mass extinctions.

General Features

Size: ~0.5 mm when fully grown.
Anatomy: 4 pairs of legs, each with 4–6 claws.
Feeding: Specialised mouth to suck nutrients from plant cells, algae, and small invertebrates.
Habitat: Tardigrades can be found almost everywhere — from the highest mountains to the deepest oceans.
- Their most common habitat, however, is the thin film of water found on mosses and lichens, which bestows upon these animals the moniker of “moss piglets”.

Resilience and Survival Abilities

Survive extreme conditions:
- Temperatures: –272.95°C to +150°C.
- Pressure: Up to 40,000 kPa (similar to ocean depths of 4 km).
- Endure Space radiation & vacuum exposure.
- Can remain viable after 30 years in frozen state.
Mechanism:
- Cryptobiosis
  - Cryptobiosis, a state in which organisms bring their metabolism to a near-complete standstill in the face of adverse environmental conditions.
  - Tardigrades can reduce their metabolism to less than 0.01% of normal
- Anhydrobiosis
  - Tardigrades drop their water levels by more than 95%, a state called anhydrobiosis

Anhydrobiosis is a remarkable biological phenomenon in which organisms can survive extreme desiccation by entering a dormant state.
It is often referred to as a form of “cryptobiosis” (hidden life), allowing life to persist under hostile conditions.
A reversible state of metabolic suspension triggered by severe water loss.
Organisms can survive with less than 1–2% of body water.
On rehydration, normal metabolism resumes.
Found in bacteria, fungi, plants (e.g., seeds, resurrection plants), and animals (tardigrades, rotifers, nematodes, brine shrimps).

- Enter “tun state” → shriveled, highly durable form.
  - Both anhydrobiosis and cryptobiosis result in the emergence of a durable shrunken state, called tun, in which tardigrades are able to withstand extreme conditions.
- CAHS proteins (cytoplasmic-abundant heat soluble) form a gel-like matrix protecting cellular components.
  - These animals produce unique proteins such as cytoplasmic-abundant heat soluble (CAHS) proteins which are key to their resilience.
  - These [proteins] form a gel-like matrix within their cells, vitrifying and protecting essential cellular components from destruction. This allows them to withstand extreme temperatures, radiation, and the vacuum of space

Scientific Importance

Understanding tardigrades’ resilience can help:
- Develop drought-resistant crops.
- Create advanced sunscreens.
- Improve tissue and organ preservation for transplantation.
- Protect astronauts from radiation and muscle/bone loss in space.

Tardigrades in Space Research

Voyager Tardigrades Experiment

The Voyager Tardigrades experiment is one of seven studies by ISRO at the ISS. It aims to explore the revival of dormant tardigrades in microgravity. The experiment will also investigate reproduction by observing eggs laid and hatched in space. Additionally, it will compare gene expression between tardigrades grown in space and those on Earth.

Scientists will take tardigrades to the ISS in a state of tun, before reviving them and examining the effects of space radiation and microgravity on their biological processes.
The primary objective of the experiment is to identify the genes that are responsible for making these animals resilient. In other words, scientists hope to pinpoint the specific molecular machinery that enables tardigrades’ survival and DNA repair in space.
This will help scientists develop strategies to protect astronauts during long-duration space missions, and preserve biological materials for extended space travel.
For instance, the survival mechanisms of tardigrades can be used to come up with strategies that better shield astronauts from space radiation, or counteract muscle and bone density loss experienced during lengthy space stays.

Earlier Missions:

2007 ESA Foton-M3 mission → ~3,000 tardigrades exposed directly to space.
Results: Many survived, some reproduced → first animals proven to survive outer space exposure.
The experiment also made tardigrades the first animal to survive exposure to space. Before water bears, animals had only survived space in the safety of a spaceship or space suit.

FAQs

Q1. What are tardigrades?

A: Tardigrades, also known as water bears or moss piglets, are microscopic, 8-legged animals capable of surviving extreme environmental conditions.

Q2. Where are tardigrades found?

A: They are found almost everywhere—from Himalayan peaks to deep sea trenches—but are most common on mosses and lichens.

Q3. What makes tardigrades so resilient?

A: Their ability to enter cryptobiosis and anhydrobiosis allows them to suspend metabolism, endure desiccation, radiation, extreme temperatures, and even space vacuum.

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