Tantulocarida is a highly specialised group of parasitic

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 that consists of about 33

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

, treated as a

class Class 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 differentl ...

in superclass

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 ...

. They are typically

ectoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s that infest

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

isopod Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...

s, tanaids, amphipods and

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

Description

Eyes are completely absent.

Body length

Members of this subclass are minute – less than in length and have a dramatic reduction in body form compared to other

s, with an unsegmented, sac-like

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

and a much reduced

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

. One tantulocarid species, ''Tantulacus dieteri'', is the world's smallest arthropod, with a total body length of only .

Life cycle

The tantulocarid life cycle is unique among crustaceans. The tantulus larva transforms directly from a non-feeding (lecithotrophic) and free-swimming organism into a parasite without any

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...

s. When entering the parasitic stage much of the body, such as the muscles, degenerates, even if the body itself becomes bigger. As a parasite it is permanently attached to its host, and after piercing its host's cuticle with an unpaired stylet, a rootlet system used to absorb nutrients enters through the hole and grow into the host’s tissue. The adult form devlopes inside the larva, and can become either a sac-like

parthenogenetic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

female, or a fully developed free-living, non-feeding and sexually-reproducing male or female. The eggs inside the parthenogenetic female are eventually released as fully developed tantulus larvae. The finding of what appears to be a benthic non-feeding nauplius larva suggests that eggs produced by sexual females hatch as nauplii instead of tantulus larvae. Both the parthenogenetic and sexual females are semelparous.

Classification

Five

families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...

are recognised: Basipodellidae Boxshall & Lincoln, 1983: *'' Basipodella'' Becker, 1975 *'' Hypertantulus'' Ohtsuka & Boxshall, 1998 *'' Nipponotantulus'' Huys, Ohtsuka & Boxshall, 1994 *'' Polynyapodella'' Huys, Møberg & Kristensen, 1997 *'' Rimitantulus'' Huys & Conroy-Dalton, 1997 *'' Serratotantulus'' Savchenko & Kolbasov, 2009 *''

Stygotantulus ''Stygotantulus'' is a genus of crustacean with the sole species ''Stygotantulus stocki''. It lives as an ectoparasite on harpacticoid copepods of the families Tisbidae and Canuellidae. It is the smallest arthropod in the world, at a length ...

'' Boxshall & Huys, 1989 Doryphallophoridae Huys, 1991: *'' Doryphallophora'' Huys, 1990 *'' Paradoryphallophora'' Ohtsuka & Boxshall, 1998 Microdajidae Boxshall & Lincoln, 1987: *'' Microdajus'' Greve, 1965 *'' Xenalytus'' Huys, 1991

Cumoniscidae Cumoniscidae is a family (biology), family of crustaceans in the Class (biology), class Tantulocarida, classified under the superclass (biology), superclass Multicrustacea. The family was previously known as Deoterthridae, but Cumoniscidae was d ...

Nierstrasz & Brender à Brandis, 1923 (formerly family Deoterthridae: *'' Amphitantulus'' Boxshall & Vader, 1993 *'' Aphotocentor'' Huys, 1991 *'' Arcticotantulus'' Kornev, Tchesunov & Rybnikov, 2004 *'' Boreotantulus'' Huys & Boxshall, 1988 *'' Campyloxiphos'' Huys, 1991 *'' Coralliotantulus'' Huys, 1991 *'' Cumoniscus'' Bonnier, 1903 *'' Deoterthron'' Bradford & Hewitt, 1980 *'' Dicrotrichura'' Huys, 1989 *'' Itoitantulus'' Huys, Ohtsuka Boxshall & Itô, 1992 *'' Tantulacus'' Huys, Andersen & Kristensen, 1992

Onceroxenidae ''Onceroxenus'' is a genus of crustaceans belonging to the monotypic family Onceroxenidae. The species of this genus are found in Western Europe. Species: *''Onceroxenus birdi'' *''Onceroxenus curtus'' References

{{Taxonbar, from=Q655 ...

Huys, 1991: *''

Onceroxenus ''Onceroxenus'' is a genus of crustaceans belonging to the monotypic family Onceroxenidae. The species of this genus are found in Western Europe. Species: *''Onceroxenus birdi'' *''Onceroxenus curtus'' References

{{Taxonbar, from=Q655 ...

'' Boxshall & Lincoln, 1987

References

External links

* {{Taxonbar, from=Q2340012 Maxillopoda Parasitic crustaceans Arthropod subclasses