Leptostraca


Leptostraca is an order of small, marine crustaceans. Its members, including the well-studied Nebalia, occur throughout the world's oceans and are usually considered to be filter-feeders. It is the only extant order in the subclass Phyllocarida. They are believed to represent the most primitive members of their class, the Malacostraca, and first appear in the fossil record during the Cambrian period.

Description

Leptostracans are usually small, typically long, crustaceans distinguished from all other members of their class in having seven abdominal segments, instead of six. Their head has stalked compound eyes, two pairs of antennae, and a pair of mandibles but no maxillipeds. The carapace is large and comprises two valves which cover the head and the thorax, including most of the thoracic appendages, and serves as a brood pouch for the developing embryos. The first six abdominal segments bear pleopods, while the seventh bears a pair of caudal furcae, which may be homologous to uropods of other crustaceans.
Leptostracans have gills on their thoracic limbs, but also breathe through a respiratory membrane on the inside of the carapace. The eggs hatch as a postlarval, or "manca" stage, which lacks a fully developed carapace, but otherwise resembles the adult.

Classification

It is now accepted that leptostracans belong to the Malacostraca, and the sister crown group to Leptostraca is Eumalacostraca.
The Order Leptostraca is divided into three families, with ten genera containing a total of around 40 validly described extant species:
SpeciesAuthorityDateFamilyDistribution
Nebaliopsis typicaSars1887NebaliopsididaeSouthern Hemisphere
Pseudonebaliopsis atlanticaPetryachov1996NebaliopsididaeNorth Atlantic
Nebalia antarcticaDahl1990NebaliidaeAntarctica
Nebalia bipesFabricius1780NebaliidaeArctic and sub-Arctic
Nebalia borealisDahl1985Nebaliidaenorth-east Atlantic Ocean
Nebalia bruceiOlesen1999NebaliidaeTanzania
Nebalia cannoniDahl1990NebaliidaeSouth Georgia
Nebalia capensisBarnard1914NebaliidaeSouth Africa
Nebalia clausiDahl1985NebaliidaeItaly
Nebalia dahliKazmi & Tirmizi1989NebaliidaePakistan
Nebalia daytoniVetter1996NebaliidaeCalifornia
Nebalia falklandensisDahl1990NebaliidaeFalkland Islands
Nebalia geoffroyiMilne-Edwards1828Nebaliidaenorth-east Atlantic Ocean
Nebalia gerkenaeHaney & Martin2000NebaliidaeCalifornia
Nebalia herbstiiLeach1814Nebaliidaenorth-east Atlantic Ocean
Nebalia hessleriMartin et al.1996NebaliidaeCalifornia
Nebalia ilheoensisKensley1976Nebaliidaesouth-western Africa
Nebalia kensleyiHaney & Martin2005NebaliidaeCalifornia
Nebalia kocatasiKocak, Moreira & Katagan2007NebaliidaeMediterranean Sea
Nebalia koreanaSong, Moreira & Min2012NebaliidaeSouth Korea
Nebalia lagartensisEscobar & Villalobos-Hiriart1995NebaliidaeMexico
Nebalia longicornisThomson1879NebaliidaeSouth Pacific, South Africa, Caribbean Sea
Nebalia marerubiWägele1983NebaliidaeRed Sea
Nebalia patagonicaDahl1990NebaliidaeMagellan region
Nebalia schizophthalmaHaney, Hessler & Martin2001Nebaliidaewestern Atlantic Ocean
Nebalia strausiRisso1826Nebaliidaenorth-east Atlantic Ocean, Mediterranean Sea
Nebalia troncosoiMoreira, Cacabelos & Dominguez2003NebaliidaeSpain
Nebaliella antarcticaThiele1904NebaliidaeKerguelen, New Zealand
Nebaliella brevicarinataKikuchi & Gamô1992NebaliidaeAntarctica
Nebaliella cabotiClark1932NebaliidaeCabot Strait, New Jersey
Nebaliella declivatasWalker-Smith1998NebaliidaeAustralia
Nebaliella extremaThiele1905NebaliidaeAntarctica
Dahlella caldariensisHessler1984NebaliidaeEast Pacific Rise
Sarsinebalia cristobiMoreira, Gestoso & Troncoso2003Nebaliidaenorth-east Atlantic Ocean
Sarsinebalia typhlops1870NebaliidaeNorth Atlantic, Australia
Sarsinebalia urgorriiMoreira, Gestoso & Troncoso2003Nebaliidaenorth-east Atlantic Ocean
Speonebalia cannoniBowman, Yager & Iliffe1985NebaliidaeTurks and Caicos Islands
Levinebalia fortunata1976ParanebaliidaeNew Zealand
Levinebalia mariaWalker-Smith2000ParanebaliidaeAustralia
Paranebalia belizensisModlin1991ParanebaliidaeBelize
Paranebalia longipes1875ParanebaliidaeAtlantic, Pacific and Indian Oceans
Saronebalia guanensisHaney & Martin2004ParanebaliidaeBritish Virgin Islands