5 Reasons We Love Water Bears

Susana Fares Mazloum

Water bears, also known as tardigrades, are considered by many specialists to be Earth’s last standing species, due to their incredible survival characteristics. Water bears are almost translucent and are about half a millimeter in length. Depending on the light, they can be seen with the naked eye. They have a defined head and four body segments, each containing a pair of legs equipped with claws.

water bear
Microscopic image of a water bear. Source: Photo Science Library

Well, we actually don’t need to say it because it’s obvious BUT: water bears are amazing creatures.

And here are 5 reasons why we love water bears:

⚪Water bears can endure excessive heat and cold temperatures

Water bears can endure and survive in extreme conditions that are considered to be lethal to most living creatures, researchers stimated that the temperatures can vary from 300 degrees Fahrenheit and as low as -328 degrees Fahrenheit. This is possible due to their ability to form a structure called a “tun” by releasing water, retracting their limbs, and curling into microscopic balls. Once the temperature is once again suitable, water bears rehydrate and restore their normal form; all this can happen without harming its organism.

⚪Water Bears hatch from their egg fully formed

In a research study, scientists observed that water bears hatched from their eggs already in their adult forms. They looked exactly like adult water bears, only insignificantly smaller in size. The only transformation they go through the years is molting, a process in which they shed their skin.

⚪Water Bears survived space radiation

Tardigrades can recover after facing unfiltered solar radiation and space’s vacuum, adding them to an “exclusive and short list of organisms” capable of doing so, researchers reported in September 2008 in the journal Current Biology.

Two species of water bears, Richtersius coronifer and Milnesium tardigradum, were exposed for a time of 10 days to space vacuum and radiation. The specimens were later successfully resuscitated and were able to return to their normal state. The fact that water bears recovered from exposure to unfiltered solar and radiation makes them one of the few organisms capable of resisting such conditions.

⚪Water Bears have their own branch on the tree of life

Llife on Earth is divided into three domains: Bacteria, Archaea and Eukarya. Eukarya is divided by taxonomists into four kingdoms: Protista, Plantae, Fungi and Animalia. Water bears are in the Phylum Tardigrade, which is one of the 36 phyla within the kingdom Animalia; thus water bears have an specific branch on the tree of life. They are considered ecdysozoa due their external body membrane that resembles a flexible cuticle.

⚪There are more than 1,000 discovered species of Water Bears

There are more than 1,000 known water bear species and new species are being discovered continuously. Just recently, a new species was discovered in a parking lot in Japan, named Macrobiotus shonaicus. It has become the 168th species discovered only from Japan.

Cool fact:
The water bear’s mouth can crumple outward resembling a telescope, revealing sharp teeth that are mainly used to capture food.

Stec D, Arakawa K, Michalczyk Ł (2018) An integrative description of Macrobiotus shonaicus sp. nov. (Tardigrada: Macrobiotidae) from Japan with notes on its phylogenetic position within the hufelandi group. PLoS ONE 13(2): e0192210. https://doi.org/10.1371/journal.pone.0192210

Rebecchi, L.; Altiero, T.; Rizzo, A. M.; Cesari, M.; Montorfano, G.; Marchioro, T.; Bertolani, R.; Guidetti, R. (July 2012). “Two tardigrade species on board of the STS-134 space flight”. 12th International Symposium on Tardigrada (PDF). p. 89. hdl:2434/239127. ISBN 978-989-96860-7-6.

Bordenstein, Sarah. “Tardigrades (Water Bears)”. Microbial Life Educational Resources. National Science Digital Library. Retrieved 2014-01-24.

Edited by Shreya Singireddy