Cephalocarida

Source: Wikipedia, the free encyclopedia.
"Horseshoe shrimp" redirects here. For a species in this class known as the horseshoe shrimp, see Hutchinsoniella. For the horseshoe shrimp better known as tadpole shrimp or shield shrimp, see Notostraca.

Cephalocarida
Temporal range: 462–0 
Ma
Hutchinsoniella macracantha
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Cephalocarida
Sanders, 1955
Order: Brachypoda
Birshteyn, 1960
Family: Hutchinsoniellidae
Sanders, 1955
Genera
Synonyms
  • Lightiellidae Jones 1961

The Cephalocarida are a class in the subphylum Crustacea comprising only 12 species. Both the nauplii and the adults are benthic.[1] They were discovered in 1955 by Howard L. Sanders,[2] and are commonly referred to as horseshoe shrimp. They have been grouped together with the Remipedia in the Xenocarida. Although a second family, Lightiellidae, is sometimes used, all cephalocaridans are generally considered to belong in just one family: Hutchinsoniellidae. Fossil records of cephalocaridans has been found in 462 million year old deposits.[3]

Taxonomy

  • Class Cephalocarida Sanders 1955[4]
    • Order Brachypoda Birshteyn 1960
      • Family Hutchinsoniellidae Sanders 1955
        • Genus Chiltoniella Knox & Fenwick 1977
          • Chiltoniella elongata Knox & Fenwick 1977
        • Genus Hampsonellus Hessler & Wakabara 2000
          • Hampsonellus brasiliensis Hessler & Wakabara 2000
        • Genus Hutchinsoniella Sanders 1955
          • Hutchinsoniella macracantha Sanders 1955
        • Genus Lightiella Jones 1961
          • Lightiella floridana McLaughlin 1976
          • Lightiella incisa Gooding 1963
          • Lightiella magdalenina Carcupino et al. 2006
          • Lightiella monniotae Cals & Delamare Deboutteville 1970
          • Lightiella serendipita Jones 1961
        • Genus Sandersiella Shiino 1965
          • Sandersiella acuminata Shiino 1965
          • Sandersiella bathyalis Hessler & Sanders 1973
          • Sandersiella calmani Hessler & Sanders 1973
          • Sandersiella kikuchii Shimomura & Akiyama 2008

Description and anatomy

These are hermaphroditic and pigmentless crustaceans with an elongated and translucent body that measures 2 to 4 mm (0.079 to 0.157 in) in length. A heart is present, and their exopods and pseudepipodites appears to be used for gas exchange.[5][6] They have a large head, the hind edge of which covers the first thoracic segment. The thorax consists of nine limb-bearing segments (thoracic limb VIII absent in Lightiella), followed by 10 limbless abdominal segments and a telson. In the larva, all the trunk segments are ring-shaped, but more dorsoventrally flattened than in the adults. During growth the anterior segments turns into the thorax and the posterior segments which makes up the abdomen remains ring-shaped.[7] No eyes have been observed in either the adult or larval stages, presumably because of their muddy natural habitat. The second pair of antennae is located behind the mouth; in all other crustaceans the antennae are in front of the mouth at the adult stage, and only their larvae have antennae that have the same location as adult cephalocaridans.[8][9]

The mouth is located behind the large upper lip, flanked by

maxillae is very small, and the second pair has the same structure as the following thoracic legs: a large basal part, equipped with outgrowths on the inner side, used in locomotion, a forked inner branch and two outer lobes - referred to as the "pseudoepipod" and the "exopod". The structural and functional similarity between the maxillae and the legs may be a sign of primitive organization; the maxillae are not specialized, as they are in other crustaceans.[8]

Ecology

Cephalocaridans are found from the

ventral groove, leading to the mouthparts.[10]

References

  1. ^ Key for the identification of crustacean nauplii - GfBS
  2. PMID 16589618
    .
  3. ^ Welsh fossils uncover an ancient 'marine dwarf world'
  4. ^ Boxshall, G. (2010). "Hutchinsoniellidae Sanders, 1955". World Register of Marine Species. Retrieved 2017-12-07.
  5. ^ Class Cephalocarida Sanders, 19551 in - Brill
  6. ^ Functional Morphology and Diversity
  7. ^ Atlas of Crustacean Larvae
  8. ^
    ISBN 978-0-03-056747-6
    .
  9. ^ Rediscovery of the horseshoe shrimp Lightiella serendipita Jones, 1961 (Cephalocarida: Hutchinsoniellidae) in San Francisco Bay, California, USA, with a key to the worldwide species of Cephalocarida
  10. ^ L. A. Zenkevich. "Phylum Arthropoda". The Animal Life [Zhizn' Zhivotnykh]. Vol. 2.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Cephalocarida&oldid=1216670459"