Tantulocarida is a highly specialised group of parasitic crustaceans that consists of about 33 species, treated as a class in superclass Multicrustacea. They are typically ectoparasites that infest copepods, isopods, tanaids, amphipods and ostracods.
Description
In the Tantulocarida, animals do not ever present eyes.
The tantulus larvae has a head with a ventral oral disc but no appendages, a six-segmented thorax with six pairs of legs, and a limbless abdomen consisting of one to six segments in addition to a telson. The larvae also possesses a cuticular stylet on the cephalon through which they can push a rootlet system for extraction of nutrients from a host. The rootlet system itself is a direct extension of the gut.
===Body length===<!-- Please check What links here? in the sidebar before changing this subheader. -->
Members of this subclass are minute – less than in length and have a dramatic reduction in body form compared to other crustaceans, with an unsegmented, sac-like thorax and a much reduced abdomen. 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 instars. 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 develops inside the larva, and can become either a sac-like parthenogenetic 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 are recognised:
Basipodellidae <small>Boxshall & Lincoln, 1983</small>:
- Basipodella <small>Becker, 1975</small>
- Hypertantulus <small>Ohtsuka & Boxshall, 1998</small>
- Nipponotantulus <small>Huys, Ohtsuka & Boxshall, 1994</small>
- Polynyapodella <small>Huys, Møberg & Kristensen, 1997</small>
- Rimitantulus <small>Huys & Conroy-Dalton, 1997</small>
- Serratotantulus <small>Savchenko & Kolbasov, 2009</small>
- Stygotantulus <small>Boxshall & Huys, 1989</small>
Doryphallophoridae <small>Huys, 1991</small>:
- Doryphallophora <small>Huys, 1990</small>
- Paradoryphallophora <small>Ohtsuka & Boxshall, 1998</small>
Microdajidae <small>Boxshall & Lincoln, 1987</small>:
- Microdajus <small>Greve, 1965</small>
- Xenalytus <small>Huys, 1991</small>
Cumoniscidae <small>Nierstrasz & Brender à Brandis, 1923</small> (formerly family Deoterthridae:
- Amphitantulus <small>Boxshall & Vader, 1993</small>
- Aphotocentor <small>Huys, 1991</small>
- Arcticotantulus <small>Kornev, Tchesunov & Rybnikov, 2004</small>
- Boreotantulus <small>Huys & Boxshall, 1988</small>
- Campyloxiphos <small>Huys, 1991</small>
- Coralliotantulus <small>Huys, 1991</small>
- Cumoniscus <small>Bonnier, 1903</small>
- Deoterthron <small>Bradford & Hewitt, 1980</small>
- Dicrotrichura <small>Huys, 1989</small>
- Itoitantulus <small>Huys, Ohtsuka Boxshall & Itô, 1992</small>
- Tantulacus <small>Huys, Andersen & Kristensen, 1992</small>
Onceroxenidae <small>Huys, 1991</small>:
- Onceroxenus <small>Boxshall & Lincoln, 1987</small>