''Kiwa'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of marine

decapods The Decapoda or decapods (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crabs, lobsters, crayfish, shrimp and prawns. Most decapods are scavengers. The order is es ...

living at deep-sea hydrothermal vents and

cold seep A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the see ...

s. The animals are commonly referred to as "yeti lobsters" or "yeti crabs", after the legendary

yeti The Yeti ()"Yeti"
''

The genus is placed in its own family, Kiwaidae, in the superfamily

Chirostyloidea Chirostyloidea is an anomuran superfamily with squat lobster-like representatives. It comprises the three families Chirostylidae, Eumunididae and Kiwaidae. Although representatives of Chirostyloidea are superficially similar to galatheoid squa ...

. Five species have been described: ''

Kiwa hirsuta ''Kiwa hirsuta'' is a crustacean discovered in 2005 in the South Pacific Ocean. This decapod, which is approximately long, is notable for the quantity of silky blond setae (resembling fur) covering its pereiopods (thoracic legs, including claws ...

'' discovered in 2005 on the

Pacific-Antarctic Ridge The Pacific-Antarctic Ridge (PAR) is a divergent tectonic plate boundary located on the seafloor of the South Pacific Ocean, separating the Pacific Plate from the Antarctic Plate. It is regarded as the southern section of the East Pacific Rise ...

, ''

Kiwa puravida ''Kiwa puravida'' is a species of deep-sea dwelling decapod, a member of the genus '' Kiwa'', a genus of animals sometimes informally known as "yeti crabs". The crabs live at deep-sea cold seeps where they feed on symbiotic Pseudomonadota, wh ...

'' discovered in 2006 at cold seeps in the East Pacific (all other species are from hydrothermal vents), ''

Kiwa tyleri ''Kiwa tyleri'', the "Hoff crab", is a species of deep-sea squat lobster in the family Kiwaidae, which lives on hydrothermal vents near Antarctica. The crustacean was given its English nickname in 2010 by UK deep-sea scientists aboard the RRS ' ...

'', known colloquially as the "Hoff crab", from the

East Scotia Ridge The Scotia Plate () is a tectonic plate on the edge of the South Atlantic and Southern oceans. Thought to have formed during the early Eocene with the opening of the Drake Passage that separates South America from Antarctica, it is a minor pla ...

, and ''

Kiwa araonae Kiwa or KIWA may refer to: * Kiwa, Mie, Japan * Kiwa (electronic music act), Finland * Kiwa NV a European institution for Testing and Certification * Kiwa (artist) (real name Jaanus Kivaste; born 1975), Estonian artist * Kiwa (mythology), a gua ...

'' from the Australian-Antarctic Ridge. Two similar but

undescribed species In taxonomy, an undescribed taxon is a taxon (for example, a species) that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and name ...

are known from vents on the

South West Indian Ridge The Southwest Indian Ridge (SWIR) is a mid-ocean ridge located along the floors of the south-west Indian Ocean and south-east Atlantic Ocean. A divergent tectonic plate boundary separating the Somali Plate to the north from the Antarctic Plate ...

and at the Galápagos respectively. Analysis of DNA has confirmed the distinction of the species, them having diverged from each other millions of years ago. The third undescribed species of ''Kiwa'' was discovered in 2010 in the Atlantic sector of the Southern Ocean at vents on the East Scotia Ridge. Compared with the first two species, it has proportionally much shorter chelae, with the majority of the bacteria-growing setae concentrated on the ventral carapace. Dense mass of anomuran crab Kiwa around deep-sea hydrothermal vent

Dense mass of anomuran crab Kiwa around deep-sea hydrothermal vent

Based on the presence of sulphur-oxidising bacteria on the

seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. T ...

e of both ''K. hirsuta'' and the new South West Indian Ridge species, they may both feed on bacteria in addition to scavenging. For ''K. puravida'', the bacteria have been identified and the feeding behaviour observed, as well as a cyclical rhythmic motion of the crab documented that is suspected to increase the flow of methane and sulfide, the bacterial food, towards the bacteria. The two sexes of the new South West Indian Ridge species prefer different temperatures, with males seeming to prefer warmer water and egg-carrying females and juveniles preferring the coldest. The genus ''Kiwa'' is named after "the goddess of the shellfish in the Polynesian mythology".

Internal anatomy

Internal anatomy has been studied in ''Kiwa puravida''. Digestive system: The stomach (gastric mill + pylorus) is situated in the upper anterior portion of the cephalothorax. The gut extends as a tube to the telson. A pair of short anterior ceca emanates from the transition between pylorus and gut, appearing as short tubes. The hepatopancreas fills most of the cephalothorax and parts of the pleon and is formed by two bunches of tubular diverticles which are each connected to the pylorus via a main duct. The stomach is embedded ventrally by the hepatopancreas whose anterior diverticles reach into the rostrum. Antennal glands: The antennal glands are flatenned and located anterolaterally in the cephalothorax, near the second antennae. the lobes of the antennal bladder are situated anteriorly and laterally to the stomach and cover a large portion of the hepatopancreas. Reproductive system: The testes are paired and restricted to the cephalothorax. They are connected to the vasa deferentia on each side which run to the gonopores on the coxae of the eighth thoracic segment. Nervous system: The brain is the anteriormost part of the central nervous system. It is relatively small compared to the rest of the body. Emanating from the brain several nerves run to the sensory organs (eyes, antennulae, antennae). A pair of circumesophageal ("surrounding the esophagus") connectives connect the brain with the cephalothoracic ganglion. The latter is a compaction of several

neuromere Neuromeres are morphologically or molecularly defined transient segments of the early developing brain. Rhombomeres are such segments that make up the rhombencephalon or hindbrain. More controversially, some argue that there exist early develop ...

s in the lower part of the anterior cephalothorax. These neuromeres correspond morphologically with the body segments of the mandibles and the 1st and 2nd maxillae, the thoracic segments I-VIII and the first pleonal segment. The 2nd to 6th pleonal neuromeres form separate ganglia. They are arranged in an irregular segmental pattern with the sixth pleonal segment reaching into the sixth pleonal segment. Circulatory system: The heart is located in the upper portion of the cephalothorax below the carapace and above the anterior portion of the gut. The heart is suspended by several ligaments within the pericardial sinus which is bordered by the pericardial septum. Three pairs of openings (ostia) connect sinus and interior heart space. The interior heart is crossed by asymmetrical arranged muscular bundles which are part of the heart muscle (myocard). Seven arteries which can be categorized into five artery systems (two paired, three unpaired) emanate from the heart and run to the respective organs and body regions. After having left the arteries and having washed around the tissues the "blood" (hemolymph) is channelled to the gill (branchial) sinus via crevices (lacunae) and channels (sinus). After its oxygenation the hemolymph is returning to the pericardial sinus via the branchio-pericardial sinus. Muscle systems: The general structure and organization of the various muscle systems in ''Kiwa'' (''puravida'') is congruent with that of other decapods.

References

External links

* * {{Taxonbar, from1=Q821026, from2=Q15894437 Squat lobsters Decapod genera