Remipedia is a class of blind

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s found in coastal

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteris ...

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

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

, and the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

. The first described remipede was the fossil ''

Tesnusocaris goldichi ''Tesnusocaris goldichi'' is an extinct species of remipedian crustacean that lived in the Pennsylvanian period, the one of the two representatives of the extinct remipedian Order Enantiopoda. Its fossil is from the Lower Pennsylvanian (Paleoz ...

'' (

Lower Pennsylvanian The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the ICS geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period. It lasted from roughly . As with most o ...

). Since 1979, at least seventeen living species have been identified in subtropical regions around the world.

Description

Remipedes are long and comprise a head and an elongate trunk of up to thirty-two similar

body segment Segmentation in biology is the division of some animal and plant body plans into a series of repetitive segments. This article focuses on the segmentation of animal body plans, specifically using the examples of the taxa Arthropoda, Chordata, an ...

s. Pigmentation and eyes are absent. Biramous swimming appendages 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 enzyme Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of anima ...

s and venom into their prey, but they also feed through

filter feeding Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

. Being

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have s ...

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 In biology, a tagma (Greek: τάγμα, plural tagmata – τάγματα - body of soldiers; battalion) is a specialized grouping of multiple segments or metameres into a coherently functional morphological unit. Familiar examples are the head ...

. 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). Based on the studies of The free-living larvae are lecithotrophic (non-feeding), and a mouth, gut and anus doesn't appear before the juvenile stage. Because of the energy and nutrients required for swimming, molt several times 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.

History of classification

The class Remipedia was erected in 1981 by Jill Yager, in describing '' Speleonectes lucayensis'' from the Bahamas. The name "Remipedia" is from the Latin ', meaning "oar-footed". Historical phylogeny based on morphology and physiology has placed Remipedia under Mandibulata, in the subphylum

Crustacea Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

, and distinct from Hexapoda. New research in evolution and development reveals similarities between larvae and postembryonic development of remipedes and

Malacostraca Malacostraca (from New Latin; ) is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobs ...

, 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 The Cephalocarida are a class in the subphylum Crustacea comprising only 12 benthic species. They were discovered in 1955 by Howard L. Sanders, and are commonly referred to as horseshoe shrimp. They have been grouped together with the Remiped ...

Branchiopoda Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Diplostraca (or Cladocera), Notostraca and the Devonian '' Lepidocaris''. They are mostly small, freshwater animals that feed on plankton and detritus. Descriptio ...

, and Hexapoda 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

are grouped together form the clade

Xenocarida Xenocarida (from the Greek for ''strange shrimp'') is a proposed clade inside the subphylum Crustacea that comprises two classes that were discovered in the 20th century: Remipedia and Cephalocarida. The clade was recovered as the sister groups to ...

, 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 The clade Multicrustacea constitutes the largest superclass of crustaceans, containing approximately four-fifths of all described crustacean species, including crabs, lobsters, crayfish, shrimp, krill, prawns, woodlice, barnacles, copepods, amp ...

, 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 ''

'' and '' Cryptocaris hootchi''. * †Order Enantiopoda Birshtein 1960 ** †Family Tesnusocarididae Brooks 1955 ryptocarididae Sieg 1980*** Genus †''

Tesnusocaris ''Tesnusocaris goldichi'' is an extinct species of remipedian crustacean that lived in the Pennsylvanian period, the one of the two representatives of the extinct remipedian Order Enantiopoda. Its fossil is from the Lower Pennsylvanian (Paleoz ...

'' Brooks 1955 **** †''Tesnusocaris goldichi'' Brooks 1955 *** Genus †'' Cryptocaris'' Emerson & Schram 1985 **** †''Cryptocaris hootchi'' Emerson & Schram 1985 * 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 Godzilliidae is a family of remipedes in the order Nectiopoda. There are at least two genera and four described species in Godzilliidae. Genera These two genera belong to the family Godzilliidae: * '' Godzilliognomus'' Yager, 1989 * '' Godzill ...

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 is a mutated, enormous spider-like kaiju that first appears in Toho's 1967 film ''Son of Godzilla'' and went on to appear in the films ''Destroy All Monsters'', ''All Monsters Attack'' (through stock footage) and '' Godzilla: Final Wars''. In the ...

'' 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 Speleonectidae is a family of remipedes in the order Nectiopoda. There are at least two genera and about seven described species in Speleonectidae. Genera These two genera and seven species belong to the family Speleonectidae: * '' Lasionectes ...

Yager 1981 *** Genus '' Lasionectes'' Yager & Schram, 1986 **** '' Lasionectes entrichoma'' Yager & Schram, 1986 *** Genus '' Speleonectes'' Yager 1981 **** '' Speleonectes cokei'' Yager, 2013 **** '' Speleonectes epilimnius'' Yager & Carpenter, 1999 **** '' Speleonectes gironensis'' Yager, 1994 **** '' Speleonectes kakukii'' 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) **** '' 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 ( el, Άνδρος, ) is the northernmost island of the 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 ...

, Sweetings Cay,

Grand Bahama Grand Bahama is the northernmost of the islands of the Bahamas, with the town of West End located east of Palm Beach, Florida. It is the third largest island in the Bahamas island chain of approximately 700 islands and 2,400 cays. The island i ...

Great Exuma Exuma is a district of The Bahamas, consisting of over 365 islands, also called cays. The largest of the cays is Great Exuma, which is 37 mi (60 km) in length and joined to another island, Little Exuma, by a small bridge. The capital ...

Great Guana Cay Great Guana Cay is an islet in The Bahamas. It is a long, narrow islet, long. It is in the centre of the Abaco Islands and is near Gumelemi Cay. It is about 8 miles from Marsh Harbour. Approximately 150 people live on the island, mostly along ...

(

Exuma Cays Exuma is a district of The Bahamas, consisting of over 365 islands, also called cays. The largest of the cays is Great Exuma, which is 37 mi (60 km) in length and joined to another island, Little Exuma, by a small bridge. The capital ...

), Cat Island,

Abaco Islands Abaco is a variant Italian form of the Biblical name "Habakkuk" (but normally Abacùc or Abacucco). Abaco may refer to: People *Evaristo Felice Dall'Abaco (1675–1742), Italian composer and violinist *Joseph Abaco (1710–1805), Belgian compose ...

San Salvador Island San Salvador Island (known as Watling's Island from the 1680s until 1925) is an island and district of The Bahamas. It is widely believed that during Christopher Columbus's first expedition to the New World, this island was the first land he ...

* –

North Caicos North Caicos is the second-largest island in the Turks and Caicos Islands (after Middle Caicos). To the west, the Caicos Cays (the closest is Parrot Cay) link to Providenciales. To the east, it is separated from Middle Caicos by Juniper Hole, a ...

Providenciales Providenciales (known locally as Provo) is an island in the northwest Caicos Islands, part of the Turks and Caicos Islands, a British Overseas Territory. The island has an area of and a 2012 Census population of 23,769. Providenciales is the la ...

* –

North West Cape North West Cape is a peninsula in the north-west of Western Australia. Cape Range runs down the spine of the peninsula and Ningaloo Reef runs along the western edge. It is in the Gascoyne region and includes the town of Exmouth. History In 161 ...

( Western Australia) * –

Matanzas Province Matanzas () is one of the provinces of Cuba. Major towns in the province include Cárdenas, Colón, Jovellanos and the capital of the same name, Matanzas. The resort town of Varadero is also located in this province. Among Cuban provinces, ...

* – Lanzarote ( Canary Islands) * –

Quintana Roo Quintana Roo ( , ), officially the Free and Sovereign State of Quintana Roo ( es, Estado Libre y Soberano de Quintana Roo), is one of the 31 states which, with Mexico City, constitute the 32 federal entities of Mexico. It is divided into 11 mu ...

*Belize -

Caye_Chapel Caye Chapel is a small, private island in Belize, north-northeast of Belize City and south of Caye Caulker. It was once owned by Isaiah Emmanuel Morter, Belize's first African millionaire. Caye Chapel is adjacent to the Bacalar Chico Na ...

* – Distrito Nacional Cueva Taína, Santo Domingo Este.

References

External links

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