Remipedia is a

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

of blind

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, closely related to hexapods, found in coastal

aquifer An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

s which contain saline groundwater, with populations identified in almost every ocean basin so far explored, including in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

, and the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

. The first described remipede was the fossil '' Tesnusocaris goldichi'' ( Lower Pennsylvanian). Since 1979, at least seventeen living species have been identified in

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

regions around the world.

Description

Remipedes are long and comprise a head and an elongate trunk of up to thirty-two similar body segments. Pigmentation and eyes are absent. Biramous swimming

appendage An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface app ...

s are laterally present on each segment. The animals swim on their backs and are generally slow-moving. They are the only known venomous crustaceans, and have fangs connected to secretory glands, which inject a combination of digestive enzymes and

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

into their prey, but they also feed through

filter feeding Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a spe ...

. Being

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

s, the female pore is located on the seventh trunk segment and the male pore on the fourteenth. Remipedia have a generally primitive body plan compared to other extant crustaceans, and are the only extant pancrustaceans to lack significant postcephalic tagmosis. External respiratory structures like gills are absent. Previously regarded as 'primitive', Remipedia have since been shown to have enhanced olfactory nerve centers (a common feature for species that live in dark environments). The larvae are free-living and appear to be lecithotrophic (non-feeding). Mouths, guts, and anuses appear in the juvenile stage. Because of the energy and nutrients required for swimming, molting, and to grow in size and length, it has been speculated that the larvae may have other sources of growth than its yolk; possibly symbiotic bacteria. With the exception of ''Speleonectes kakuki'', which inhabits a fully marine, sub-seafloor cave in the Bahamas, all known species of remipedians have been found exclusively in anchialine cave systems.

History of classification

The first species in this group to be described was '' Speleonectes lucayensis'', discovered by Jill Yager while cave diving in Lucayan Caverns on the Grand Bahama Island in 1979 and described in a paper in the ''

Journal of Crustacean Biology The ''Journal of Crustacean Biology'' is a quarterly peer-reviewed scientific journal in the field of carcinology (crustacean research). It is published by The Crustacean Society and Oxford University Press (formerly by Brill Publishers and Alle ...

'' in 1981. The novel nature of this species was recognized and the class Remipedia was erected in the same paper. The name "Remipedia" is from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

', meaning "oar-footed". Historical phylogeny based on morphology and physiology has placed Remipedia under Mandibulata, in the subphylum Crustacea, and distinct from

Hexapoda The subphylum Hexapoda (from Greek for 'six legs') or hexapods comprises the largest clade of arthropods and includes most of the extant arthropod species. It includes the crown group class Insecta (true insects), as well as the much smaller c ...

. New research in evolution and development reveals similarities between larvae and postembryonic development of remipedes and

Malacostraca Malacostraca is the second largest of the six classes of pancrustaceans behind insects, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crab ...

, singling Remipedia as a potential crustacean sister group of Hexapoda. Similarities in brain anatomy further support this affinity, and hexapod-type hemocyanins have been discovered in remipedes. Recent molecular studies have grouped Remipedia with Cephalocarida, Branchiopoda, and

in a clade named Allotriocarida. Remipedia was found as the sister group to Hexapoda both in phylogenomic and combined morphological and transcriptome studies. In other studies Remipedia and Cephalocarida are grouped together form the clade Xenocarida, which in turn was sister to Hexapoda in a clade named Anartiopoda or Miracrustacea ('surprising crustaceans'). The relationship of Remipedia and other crustacean classes and insects is shown in the following phylogenetic tree, which shows Allotriocarida, along with Oligostraca and Multicrustacea, as the three main divisions of subphylum Pancrustacea, embracing the traditional crustaceans and the hexapods (including insects).

Classification

Thirty extant species are recognized as of early 2022, divided among eight families and twelve genera. All are placed in the order Nectiopoda. The second order, Enantiopoda, comprises the fossil species '' Tesnusocaris goldichi'' and '' Cryptocaris hootchi''. * †Order Enantiopoda Birshtein 1960 ** †Family Tesnusocarididae Brooks 1955 ryptocarididae Sieg 1980*** Genus †'' Tesnusocaris'' Brooks 1955 **** †''Tesnusocaris goldichi'' Brooks 1955 *** Genus †'' Cryptocaris'' Schram 1974 **** †''Cryptocaris hootchi'' Schram 1974 * Order Nectiopoda Schram 1986 **Family Micropacteridae Koenemann, Iliffe & van der Ham 2007 *** Genus '' Micropacter'' Koenemann, Iliffe & van der Ham 2007 **** ''Micropacter yagerae'' Koenemann, Iliffe & van der Ham 2007 ** Family Godzilliidae Schram, Yager & Emerson 1986 *** Genus '' Godzilliognomus'' Yager 1989 **** '' Godzilliognomus frondosus'' Yager, 1989 **** '' Godzillognomus schrami'' Iliffe, Otten & Koenemann 2010 *** Genus '' Godzillius'' Schram ''et al.'', 1986 **** '' Godzillius fuchsi'' Gonzalez, Singpiel & Schlagner 2013 **** '' Godzillius robustus'' Schram, Yager & Emerson 1986 ** Family Kumongidae Hoenemann et al. 2013 *** Genus '' Kumonga'' Hoenemann et al. 2013 **** '' Kumonga exleyi'' (Yager & Humphreys 1996) Hoenemann et al. 2013 'Lasionectes exleyi'' Yager & Humphreys 1996** Family Cryptocorynetidae Hoenemann et al. 2013 *** Genus '' Kaloketos'' Koenemann, Iliffe & Yager 2004 **** '' Kaloketos pilosus'' Koenemann, Iliffe & Yager 2004 *** Genus '' Angirasu'' Hoenemann et al. 2013 **** '' Angirasu benjamini'' (Yager 1987) Hoenemann et al. 2013 'Speleonectes benjamini'' Yager 1987**** '' Angirasu parabenjamini'' (Koenemann, Iliffe & van der Ham 2003) Hoenemann et al. 2013 'Speleonectes parabenjamini'' Koenemann, Iliffe & van der Ham 2003*** Genus '' Cryptocorynetes'' Yager 1987 **** '' Cryptocorynetes elmorei'' Hazerli, Koenemann & Iliffe 2009 **** '' Cryptocorynetes haptodiscus'' Yager 1987 **** '' Cryptocorynetes longulus'' Wollermann, Koenemann & Iliffe 2007 ** Family Morlockiidae García-Valdecasas 1984 *** Genus '' Morlockia'' García-Valdecasas 1984 **** '' Morlockia williamsi'' (Hartke, Koenemann & Yager 2011) 'Speleonectes williamsi'' Hartke, Koenemann & Yager 2011**** '' Morlockia emersoni'' (Lorentzen, Koenemann & Iliffe 2007) 'Speleonectes emersoni'' Lorentzen, Koenemann & Iliffe 2007**** '' Morlockia atlantida'' (Koenemann et al. 2009) Hoenemann et al. 2012 'Speleonectes atlantidus'' Koenemann et al. 2009**** '' Morlockia ondinae'' García-Valdecasas 1984 'Speleonectes ondinae'' (Garcia-Valdecasas 1984)** Family Speleonectidae Yager 1981 *** Genus '' Lasionectes'' Yager & Schram, 1986 **** '' Lasionectes entrichoma'' Yager & Schram, 1986 *** Genus '' Speleonectes'' Yager 1981 **** '' Speleonectes epilimnius'' Yager & Carpenter, 1999 **** '' Speleonectes gironensis'' Yager, 1994 **** '' Speleonectes kakuki'' Daenekas ''et al.'', 2009 **** '' Speleonectes lucayensis'' Yager, 1981 **** '' Speleonectes minnsi'' Koenemann, Iliffe & van der Ham, 2003 **** '' Speleonectes tanumekes'' Koenemann, Iliffe & van der Ham, 2003 ** Family Xibalbanidae Olesen et al. 2017 *** Genus '' Xibalbanus'' Hoenemann et al. 2013 **** '' Xibalbanus cokei'' (Yager, 2013) Olesen et al. 2017 'Speleonectes cokei'' Yager, 2013**** '' Xibalbanus cozumelensis'' Olesen, Meland, Glenner, van Hengstum & Iliffe, 2017 **** '' Xibalbanus fuchscockburni'' (Neiber et al. 2012) Hoenemann et al. 2013 'Speleonectes fuchscockburni'' Neiber et al. 2012**** '' Xibalbanus tulumensis'' (Yager 1987) Hoenemann et al. 2013 'Speleonectes tulumensis'' Yager 1987** Family Pleomothridae Hoenemann et al. 2013 *** Genus '' Pleomothra'' Yager 1989 **** '' Pleomothra apletocheles'' Yager 1989 **** '' Pleomothra fragilis'' Koenemann, Ziegler & Iliffe 2008

Geographic distribution of extant Remipedia

* –

Andros Andros (, ) is the northernmost island of the Greece, Greek Cyclades archipelago, about southeast of Euboea, and about north of Tinos. It is nearly long, and its greatest breadth is . It is for the most part mountainous, with many fruitful and ...

, Sweetings Cay, Grand Bahama, Great Exuma, Great Guana Cay ( Exuma Cays), Cat Island,

Abaco Islands The Abaco Islands lie in the north of Bahamas, The Bahamas, about 193 miles (167.7 nautical miles or 310.6 km) east of Miami, Florida, US. The main islands are Great Abaco and Little Abaco, which is just west of Great Abaco's northern tip. T ...

, San Salvador Island * – North Caicos, Providenciales * – North West Cape (

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

) * – Matanzas Province * –

Lanzarote Lanzarote (, , ) is a Spanish island, the easternmost of the Canary Islands, off the north coast of Africa and from the Iberian Peninsula. Covering , Lanzarote is the fourth-largest of the islands in the archipelago. With 163,230 inhabi ...

(

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

) * –

Quintana Roo Quintana Roo, officially the Free and Sovereign State of Quintana Roo, is one of the 31 states which, along with Mexico City, constitute the 32 administrative divisions of Mexico, federal entities of Mexico. It is divided into municipalities of ...

* - Caye Chapel * – Distrito Nacional Cueva Taína, Santo Domingo Este.

References

External links

* {{Taxonbar, from=Q490800 Arthropod classes Extant Pennsylvanian first appearances