• Youmna Hasanin

Kiwaidae: The Yeti Crabs

Named after a mythical monstrous creature, the yeti crab was first distinguished by its "hairy" filamentous-bacteria containing pincers (a hinged and sharply pointed organ used by an arthropod for feeding or defence, as the mandibles of an insect, or each of the chelae of a crab, lobster, or scorpion), and strongly reduced, pigment-less eyes. Due to this, it is thought to be blind.

Source: https://www.wired.com/2011/12/yeti-crab-arms-food/


Discovered back in 2005 in the floors of the South Pacific Ocean, the yeti crab resembled not only a new species, but also a new family: the Kiwaidae family. It was named Kiwa hirsuta; 'Kiwa' referring to a Polynesian deity associated with the ocean (shellfish in particular), and 'hirsuta' meaning 'hairy' in Latin.


Currently, the Kiwaidae family consists of only five species, with the yeti crab (Kiwa hirsuta) being the pioneering species of the family.


Yeti crabs tend to be found, and therefore supposedly live, in the deep oceans in hydrothermal vents. These vents are fissures on the seafloor from which geothermally heated water is released. They provide the hot water which makes up the yeti crabs' environment.

On a side note, a new study suggests that these hydrothermal vents are where life originated. The theory is currently backed up by a lot of evidence, yet it is not a popular theory, nor is it discussed often (there are also many competing theories that suggest life began in shallow pools of water).


Back to the yeti crab - its 'hairy' pincers which it is known for, contain filamentous bacteria. It is thought that the crustacean may use the bacteria to detoxify poisonous minerals (methane and sulphide) from the geothermally-heated water released through the hydrothermal vents. The process is known as chemosynthesis; whereby bacteria create food through the detoxification of such chemicals/minerals. Another similar species of yeti crab, called the Kiwa puravida (discovered in 2006, a year apart from the Kiwa hirsuta) has been observed waving its pincers over the hydrothermal vents. This motion provides a good, constant supply of oxygen and sulphide gas, which allows the bacteria to keep growing on their pincers, making them good enough to eat. The Kiwa hirsuta has been also observed behaving in a very similar manner, whereby they drape their furry claws over hydrothermal vents. As a result, scientists believe it is 'farming' a colony of bacteria on its claws in order to feed on them. Through lipid an isotope analysis, evidence has suggested that the epibiotic bacteria that lives on the Kiwa hirsuta's pincers are its main source of food, although it is generally thought to be a carnivore - it also eats mussels.


Despite being commonly referred to as the 'furry lobster', it is considered a squat lobster; more closely related to crabs and hermit crabs than actual lobsters.


Although the first yeti crab species was discovered back in 2005, it is thought that the yeti crabs have actually been around for a very long time. A 2013 analysis of their genes suggests that the Kiwaidae family evolved about 30 million years ago, about the same time when it is believed that their ancestors first colonised hydrothermal vents and cold seeps. Moreover, despite being identified only in areas of the ocean with hydrothermal vents, it is believed they probably dwell in other areas too, such as ones with rotting whale carcasses, sunken wood (shipwrecks) and algae. This is because the whale carcasses, wood and algae would all provide the necessary minerals for the bacteria on the yeti crabs' arms to grow, thus making them a good food source for the yeti crab.


Since the climate in the depths of the ocean tends to be extreme, and the yeti crabs are undoubtedly well-adapted to it, it is considered unlikely that the yeti crabs would face endangerment/extinction. Extreme climates such as these tend to remain stable, unaffected, unlike the climates on the surface of the ocean and above. Yet, as climate change continues to worsen and the earth becomes warmer, there is always potential that even the most extreme climates would be altered, forcing their inhabitants (the yeti crab), into extinction if they're unable to adapt. When considering elements such as these, it is important to consider that the issue of global warming goes way beyond the surface of what we are able to see, such as forest fires, melting glaciers and hotter summers. Instead, global warming may be already affecting and killing hundreds of undiscovered species, pushing them into extinction.


References

https://en.wikipedia.org/wiki/Kiwa_hirsuta

https://ocean.si.edu/ocean-life/invertebrates/yeti-crab

http://www.bbc.com/earth/story/20170412-in-the-deep-sea-there-live-crabs-that-look-like-yetis

https://www.wired.com/2011/12/yeti-crab-arms-food/

https://en.wikipedia.org/wiki/Kiwaidae#:~:text=Kiwa%20is%20a%20genus%20of,Kiwaidae%2C%20in%20the%20superfamily%20Chirostyloidea.

https://factanimal.com/yeti-crab/


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