A recently discovered group of crustaceans called yeti crabs (genus Kiwa, order Decapoda) have added to the number of extraordinary and previously unknown species inhabiting the harsh, inhospitable environment around hydrothermal vents on the deep seafloor. So far, three species have been identified. Kiwa hirsuta was discovered in 2005 at a hydrothermal site south of Easter Island in the Pacific Ocean at depths of 2200 meters (7220 feet). Kiwa puravida was found in Pacific waters at depths of 1000 meters (3280 feet) off Costa Rica and described in 2011. Kiwa tyleri was located at two hydrothermal vent sites in the Antarctic Ocean at depths of 2400–2600 meters (7875–8530 feet) and described in 2015. Molecular and phylogenetic analyses have confirmed the placement of these species into a new family, Kiwaidae, of decapod crustaceans. See also: Arthropod evolution and phylogeny; Biodiversity; Census of Marine Life; Crustacea; Decapoda; Deep-sea fauna; Marine biological sampling; Oceanography
Measuring up to 15 centimeters (5.9 inches), the yeti crabs inhabit hydrothermal vent sites, which are discrete mounds and sulfide chimneys emitting hot fluids on the ocean floor. Dense biologic communities live on and around these hydrothermal structures because the hot fluids emanating from the Earth's crust warm the surrounding water temperatures to habitable levels. The warmer temperatures of these areas also allow an abundance of bacteria life to thrive, which in turn forms the base of the food chain for these unusual ecosystems. The bacteria provide the main diet for many marine creatures, including the yeti crabs, which have adapted morphologically in an extraordinary way to attract and capture these bacteria. Specifically, the yeti crabs possess dense, long, plumose setae (bristling hairlike structures) on the surfaces of their long appendages. Because the white or yellowish "furry" appearance of the setae reminded investigators of the legendary Yeti, the hairy abominable snowman of the Himalayas, the term yeti crab was adopted as the common name of this animal. Investigators have determined that most of the setae have clusters of chemosynthetic, sulfide-oxidizing bacteria living on them. Thus, the setae have been hypothesized to serve as gardens for growing the crabs' main food source (that is, the bacteria). This type of feeding strategy is a plausible one, as it has been used by a number of other crustaceans inhabiting hydrothermal vents and methane seeps. In addition, yeti crabs have been observed to scavenge for and consume mussel tissues. See also: Bacteria; Ecological communities; Hydrothermal vent; Marine ecology; Marine microbiology; Trophic ecology