Yeti crab
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Yeti crab ( Kiwa hirsuta ) |
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| Scientific name | ||||||||||||
| Kiwa hirsuta | ||||||||||||
| Macpherson , Jones & Segonzac , 2005 |
The Yeti Crab ( Kiwa hirsuta , English yeti crab ) is a type of crustacean from the Kiwaidae family . It lives on the hydrothermal fields of the deep sea at a depth of about 2200 meters. These fields are characterized by chimneys, the so-called black smokers . It got its common name because of its completely white appearance and bristles on the limbs. The namesake was the mythical creature Yeti .
morphology
Size and color
The carapace of the yeti crab was 5.15 centimeters long with the holotype , including the rostrum 5.86 centimeters long. Including the chelipedes (scissors), the animal measures about 15 centimeters when stretched. The carapace is about a third longer than it is wide. The yeti crab is completely white except for yellow thorns on the extremities of the chelipedas.
anatomy
The dorsal surface of the carapace is smooth; The width and length of the Telsons (rearmost body segment) are roughly the same. The telson is divided into a front and a rear part by a transverse seam.
The front lip is slightly sloping and characterized by small teeth near the rostrum. The broad and triangular rostrum is dorsally (backwards) slightly concave. Furthermore, it is rough on the side with long bristles and the ventral (lower or belly) side is bowl-shaped. A sloping, central suture (seam) separates the front from the back of your body. The attachment of the fifth pereiopods is not visible, it can be found under the plastron (shield of the "belly", located ventrally ).
The way of life in the completely lightless deep sea was accompanied by a reduction in the eyes : in the yeti crab they are only present as a membranous rudiment without pigments , which results in blindness . Hence, the yeti crab has to rely on its antennae and other senses ; possibly the bristles play a role in the perception as sensors of water eddies and other things. The antennas are missing scales.
Both running legs and chelipeds are covered by dense bristles and a number of rows of spines. The spines of the yeti crab are characterized by a grainy, yellow pattern and a "tuft" of long, feather-like, dense bristles. The bristles are denser towards the center and towards the abdomen than to the sides and back. The spines on the front parts of the chelipedas lack this tuft-like structure.
The chelipedas are approximately symmetrical, triangular and a little more than twice as long as the carapace with rostrum. They are not occupied by bristles. The spines on the scissors get smaller the farther they are from the trunk, and eventually become completely absent. The fingers are mobile, and towards the body there is a sharp edge with smooth, flat scales, especially in the middle, a serrated area.
Bristles
The bristles are one of the special features of the yeti crab, as they are present in very large numbers. The peraeopods and partly also the chelipedas are covered with such bristles. The bristles are very flexible, around 15 millimeters long, and especially in the distal area , i.e. away from the body, are covered with thread-like bacteria . These bacteria are believed to be part of the diet. Some bristles are only 13 millimeters long on average and are not occupied by bacteria, but are much harder, have barbs and end in a thorn.
Way of life
As with other deep-sea dwellers, only sparse knowledge is available about the way of life of the yeti crab. The animals occur at a density of one to two animals per 10 square meters in the vicinity of active hydrothermal vents or at the base of such vents. They live there together with mussels of the genus Bathymodiolus , crustaceans of the genus Munidopsis , crabs of the genus Bythograea and sea snails from the family Buccinidae . The animals are probably omnivorous as well as related crabs; Upon discovery, yeti crabs were seen eating the flesh of clams damaged by the foraging activities.
distribution
So far, occurrences of the yeti crab are known from three hydrothermal fields. These are Sebastian's Steamer (37 ° 47′48 ′ S, 110 ° 54′85 ′ W, depth 2204 meters), Pâle Étoile (37 ° 47′36 ′ S, 110 ° 54′85 W, depth 2215 meters ) and Annie's Anthill (37 ° 46′49 ′ S, 110 ° 54′72 ′ W, depth 2228 meters). All three fields are close together in the southern Pacific , south of Easter Island . There may still be deposits in other hydrothermal fields. It is currently believed that the Juan Fernandez Plate , a small tectonic plate , geologically marks the northern limit of the Yeti Crab's range.
In the Atlantic , an isolated habitat at a similar temperature is populated by the Hoff crab , which has also developed a similar diet.
Systematics
Within the crustacea , the yeti crab is in the group of medium crabs (anomura); contrary to what the misleading name suggests, the animal does not belong to the group of crabs (brachyura). Because of its many unique characteristics, a separate superfamily was established for the yeti crab, the Kiwaoidea. Molecular biological studies on the DNA from the muscles of the Yeti crab have also shown clear differences to other groups of crustaceans and to other families of the Galatheoidea (jumping crabs and porcelain crabs).
Apparently, the Kiwaidae family is closer to the Chirostylidae , Galatheidae ( jumping crabs ) and Porcellanidae ( porcelain crabs ) than the Aeglidae . The superficial similarities to Chirostylidae consist of common features to the antennas and the third Maxillpeden , a transverse seam at Telson and the sternum without one plate of the last located on the thorax Thus . There are also some similarities to the Aeglidae, in the form of sternites between the third maxillipedas, but in the Aeglidae calcified structures that look like lines separate the carapace into different regions. These lines do not exist in the Kiwaidae. The clear differences between the Chirostylidae and the Kiwaidae include the missing antenna scales and the reduced eyes in the Yeti crab, the larger sternite between the third maxillipedes in the Kiwaidae family, the invisible attachment of the fifth peraeopods and several other features, among other things the presence of furrows on the surface of the carapace of Kiwa .
Following recent studies, the Kiwaidae family was placed in the superfamily Chirostyloidea . After the discovery of a second Kiwa species ( Kiwa puravida ), the genus is no longer monotypical .
Research history
The yeti crab was identified by scientists Enrique Macpherson (Spain, Centro de Estudios Avanzados de Blanes (CSIC)), William Jones (USA, Monterey Bay Aquarium Research Institute (MBARI)) and Michel Segonzac (France, Ifremer ) in 2005 Kiwa hirsuta first described. The generic name Kiwa is also the name for the Polynesian goddess of crustaceans (the Yeti crab was discovered about 1500 kilometers south of Easter Island), the second part ( epithet ) of the scientific name, hirsuta , means "hairy". The research vessel PAR 5 ( Pacific-Antarctic Ridge 5 ) drove to the aforementioned hydrothermal fields in an expedition organized by MBARI between March and April . The crab was collected on the deep-sea submarine Alvin . Only Michel Segonzac from Ifremer was present on the expedition.
The holotype captured there is now preserved in the Ifremer in Brest .
The species was discovered but not collected and described much earlier by the German research vessel Sonne SO-157 in 2001. Because of its strange appearance, which is somewhat reminiscent of a Yeti due to the bristles, the crab became so popular that in Replicas of the yeti crab came on the market in the first few weeks after its discovery in Japan.
supporting documents
Individual evidence
- ↑ KE Schnabel, ST Ahyong, EW Maas: Galatheoidea are not monophyletic - Molecular and morphological phylogeny of the squat lobsters (Decapoda: Anomura) with recognition of a new superfamily . In: Molecular Phylogenetics and Evolution . tape 58 , 2011, p. 157–168 ( PDF, 1.3MB [accessed January 24, 2013]).
- ^ AR Thurber, WJ Jones, K. Schnabel: Dancing for Food in the Deep Sea: Bacterial Farming by a New Species of Yeti Crab . In: PLoS ONE . tape 6 , no. 11 , 2011, doi : 10.1371 / journal.pone.0026243 .
- ↑ J. Stecher, M. Türkay & C. Borowski: Faunal assemblages on the Pacific-Antarctic Ridge near the Foundation Seamount Chain (37 ° 30'S, 110 ° 30'W). Cah. Biol. Mar. 43, 2002: pp. 271-274, cit. in: M. Segonzac: Kiwa hirsuta . In: D. Desbruyeres, M. Segonzac & M. Bright (Eds.): Handbook of Deep Sea Hydrothermal Vent Fauna. Denisia 18, 2006: pp. 450–451 online as pdf
- ↑ Claire Nouvian: The Deep - Life in the deep sea. German translation of the French original edition, Knesebeck Verlag, 2006: p. 219. ISBN 3-89660-376-0
literature
- M. Segonzac: Kiwa hirsuta . In: D. Desbruyères, M. Segonzac & M. Bright: Handbook of deep-sea hydrothermal vent fauna . Denisia 18, pp. 450–451, 2006 ISBN 3-85474-154-5 online as PDF
- E. Macpherson, WJ Jones & M. Segonzac: A new squat lobster family of Galatheoida (Crustacea, Decapoda, Anomura) from the hydrothermal vents of the Pacific-Antarctic-Ridge . Zoosystema, 27, 4, pp. 709–723 online as PDF (with pictures)
