Yeti Crabs: Characteristics, alimentation habits,habitat and more….

If you want to know everything we have for you about the yeti crabs or  kiwa hirsuta, then don´t miss this article, so you will be surprised with many things you probably didn´t know

His name was granted in honor to the goddess of Polynesian myths, which was called Kiwa. It receives the second name of yeti crab because of its white color and its tweezers which are uneven. Moreover, it can seem that it has hairs, but it is actually setae (similar to fur) what it has.

Discovery of the Yeti Crabs

These crabs were observed for first time in March 2005, by the marine researchers in the submarine Alvin, who were exploring hydrothermal vents along the Pacific Antarctic ridge, in the south of Easter Island. Their hairy legs granted them the nickname of “Yeti crabs,” just like the Yeti the abominable monster of the Himalayas.

The Yeti crab was discovered during an expedition to the southeast Pacific, led by the Monterey Bay Aquarium Research Institute scientist Bob Vrijenhoek. During one Alvin´s dive, the researchers noticed an unusual crab of 15-cm-length,with hairy arms on the seafloor. They grabbed the creature to study it properly.

More of these unusual crabs which live at depths of 2,200 meters were observed during subsequent Alvin dives. They were found on lava flows and areas where warm water was seeping out of the sea floor. According to the MBARI biologist Joe Jones, “Many of the crabs were hiding underneath or behind rocks—all we could see were the tips of their arms sticking out.”

The researchers noted that they had found an entirely new family called later Kiwaidae.  The Yeti crabs are distant relatives to the hermit crabs  and they are called crabs because of their anatomy, which is quite similar than that of crabs. However, they are not crabs despite their similar anatomical characteristics; they belong to the previously mentioned Kiwaidae family.

Yeti Crabs’ Main Characteristics

In terms size the yeti crabs measure a little more than 15 centimeters, and their most outstanding feature relies in their long tweezers full of hairs. Moreover, such hairs are actually setae where clusters of filamentous bacteria live, which protect the yeti crabs from many viruses that can be found around them. The setae are also distributed throughout the chelipeds and the legs of the yeti crabs.

Many scientists claim, that these setae are responsible for completely eliminating many evils that are in the water, such as poisonous minerals emitted by the hydrothermal vents where they live. Although they are called crabs, their shape  is similar to that of prawns. The yeti crabs can´t see, that is they are blind, and they only have a membrane in the place where their eyes should be located. Their shell is completely white and smooth.

Anatomical Characteristics

The anatomy of the Yeti Crabs is a little different than that of other crabs and we list their most outstanding characteristics following:

Their shell is 1.3 times longer than broad while their surface is soft. The beak of the Yeti Crabs is broadly triangular, slightly concave and it also has setae.Eyes strongly reduced, membranous remains, without pigment.. They have a symmetric telson ( as wide as long). Their chelipeds and legs have several rows of thorns, each thorn with yellow corneal tip populated dense plumose setae. Their fingers are somewhat triangular and they lack of setae. Yeti crabs possess  paired pleopods

 Yeti Crabs Reproduction

There is no significant information regarding the reproduction of the  yeti crabs , given its recent discovery and difficult location. Studies on this subject are being developed but there are no detailed results on it yet.

Let´s keep learning

 Yeti Crabs’ Nutritional Habits

The alimentation way of these peculiar crabs may seem very strange for many people, as it is not similar to that of other crabs. ( see our aticle crabs, for a detailed information of other especies of crabs)

In this aspect, the yeti crabs are very different from others, since they feed on the bacteria they have in their tweezers. Different substances, such as the fatty acids that have been found inside the bodies of these creatures confirm this statement. This is a common fact of those species that live in the deepest areas of the oceans, which don´t have access to the sunlight. They employ chemical energy from the sea floor instead.

Many specialists claim that all the bacteria that they have in their claws are filamentous, and that helps them so that they can live more calmly under the ocean.

The bacteria get energy from the inorganic gases of the methane seeps, which are sites on the ocean floor that expel methane and hydrogen sulphide gas.

After observing the behavior of these crabs, the specialists claim that they wave their claws through the water. Such movement provides the bacteria a constant flow of oxygen and sulfide gas, which seems to help them grow.

This is a common behavior of the species that live at the hydrothermal vent communities. The hot water that comes from the vent has enormous quantities of dissolved minerals, as well as a large population of chemoautotrophic bacteria. These bacteria employ hydrogen sulfide, to produce organic material through the process of chemosynthesis. So, this whole process is the basis of the dietof every species that inhabit at the hydrothermal vents.

On the other hand, there are several scientists who claim that yeti crabs are carnivores, because they have a stomach similar to other species of crabs which suggests that they can also feed on fragments of algae or other microorganisms that reach their deep habitats.

Thus there are still many aspects about the yeti crabs that need to be studied.

Yeti Crabs’ Habitat

Yeti crabs live at the bottom of the oceans. As we have mentioned before, they live in locations where the hydrothermal vents expel out boiling hot water into the cold sea above. This means that temperature goes from scalding to chilling, and in addition the pressure is quite intense and there is no light.

They need to be located near the fluid being released from the seafloor, which only comes out in certain areas.  So, they crowd such areas to have access to their so required sulfide gas. These environmental conditions entail that the yeti crabs have a really small livable area, since if they get too close to the vent they would be boiled alive, and if they get too far from it they would lose the sulfide gas, and could also die of hyperthermia

Now, let´s learn about the hydrotermal vents.

Other Species of  Yeti Crabs

In addition to the species kiwa hirsuta previously described, there are other species of yeti crabs that have been recently discovered

Kiwa puravida

This species was discovered in 2006 in cold seeps on the sea bottom of the coast of Costa Rica. They have similar anatomical characteristics than those of kiwa hirsuta and they also feed on symbiotic bacteria. The name of this species which means “pure life” in English, is related to a common saying from Costa Rica. The kiwa puravida live in methane seeps at depths of 1007 meters. This

yeti crabs: kiwa puravida

Kiwa Tyleri

This species was discovered in 2010 during an expedition to explore the hydrothermal vents on the East Scotia Ridge from the Southern Ocean, Antarctica.

The anatomical characteristics of this species are somewhat different than those of the Kiwa Puravida and the Kiwa Hirsuta, since they have short chelae and most of their setae are concentrated on their ventral surface. In fact, this particular feature is the origin of their nickname «Hoff crabs«, related to the hairy chest of the actor David Hasselhoff.

Finally  it´s quite  important to point out that this is the only species of genus crabs that lives outside the Pacific.

Kiwa araonae

This species was discovered in 2013, next to the hydrothermal vents about 2000 m down along the Australian-Antarctic Ridge. This species differs anatomically from the others by having an almost flat branchial region, a short beak and slender chelas. Moreover they are not particularly hairy.

There is another undescribed species of yeti crabs from vents on the South West Indian Ridge.All the known species of yeti crabs are distributed in the southern hemisphere throughout the oceans bordering Antarctica. However, in 2000 a study was published on a fossil of more than 100 million years of existence, which is now known to be related to the yeti crabs.

The fossil in question called Pristinapine gelaspina, was found in Alaska. This means that it is likely that there are many more species of these crabs distributed throughout the world. It is important to point out there are other places in the deep sea that have similar conditions than those of vents and seeps; especially those where the remains of other animals such as dolphins, whales, sharks even wood are found.

Abyssal Species

The yeti crabs pertain to the abyssal species, that is to say; those that are in the depths of the sea.  As we already know they live only in the mysterious hot waters.

The Hydrothermal vents and cold seeps where the yeti crabs inhabit, are commonly found in places that are volcanically active, where magma is relatively close to the surface of the planet. Hydrothermal vents are abundant on Earth because it is geologically active and has large amounts of water on their surface.

The hot springs, fumaroles and geysers can be listed as the most common hydrothermal vents on earth. In addition, The Pompeii worms and the giant tube worms are other characteristic species of these habitats. One of the characteristics of the deep-sea species is that unfortunately they are not very striking for people, or maybe they are, but not precisely because of their beauty, but remember that the earth needs biodiversity and that living beings are necessary for one reason or another.

Are Yeti Crabs Endangered?

According to investigations of the New Oxford University, different types of environmental changes may have highly impacted the geographic range and species diversity of this family. The final results indicate that such creatures may be more vulnerable to the effects of human resource exploitation and climate change than what we usually think.

The researchers showed a detailed genetic analysis of the yeti crabs, featuring all known species for the first time and revealing many aspects about their evolution. One of the most important conclusions of such study is that today’s yeti crabs are likely descended from a common ancestor that lived in deep sea hydrothermal vents on mid-ocean ridges in the South East Pacific, between 30 and 40 million years ago.

After comparing the current locations of the yeti crabs with their history of diversification, the authors suggest that these crustaceans probably existed in large regions of mid-ocean ridge in the Eastern Pacific, but they have disappeared from those areas trough the years. The reasons for this situation are not totally clear, but it is speculated that the changes in the sea oxygen levels as a consequence of climate change are the main reason.

According to Christopher Roterman, co-lead author and postdoctoral researcher in of Oxford’s Department of Zoology, “you can intuit from the results of the study that hydrothermal vent species have gone extinct in large areas. The current  locations of these animals are not necessarily indicative of their historical distribution.”

There is always something that can be done

Yeti Crabs in Captivity.

For those who have the question, about the feasibility of keeping this species in domestic aquariums the answer is not yet completely known. To date, no such cases have been reported, but due to the very peculiar conditions of the habitat where they develop, it is intuited that they would not survive in a completely different habitat, without the necessary characteristics for their feeding.

Don´t say good bye without leraning also about cold seeps.


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