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Horseshoe Shrimps

Cephalocarida

Brief Summary

    Cephalocarida: Brief Summary
    provided by wikipedia
    "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.

    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 shrimps. 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. Though no fossil record of cephalocaridans has been found, most specialists believe them to be primitive among crustaceans.

Comprehensive Description

    Cephalocarida
    provided by wikipedia
    "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.

    The Cephalocarida are a class in the subphylum Crustacea comprising only 12 benthic species. They were discovered in 1955 by Howard L. Sanders,[1] and are commonly referred to as horseshoe shrimps. 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. Though no fossil record of cephalocaridans has been found, most specialists believe them to be primitive among crustaceans.

    Taxonomy

    • Class Cephalocarida Sanders 1955[2]
      • 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 crustaceans are from 2 to 4 mm (0.079 to 0.157 in) in length, with an elongated body. They have a large head, the hind edge of which covers the first thoracic segment. They have no eyes, 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.[3]

    The mouth is located behind the large upper lip, flanked by mandibles. The first pair of 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.[3]

    The thorax consists of 10 segments, and the abdomen bears a telson but no other appendages.

    Ecology

    Cephalocaridans are found from the intertidal zone down to a depth of 1,500 m (4,900 ft), in all kinds of sediments. Cephalocaridans feed on marine detritus. To bring in food particles, they generate currents with the thoracic appendages like the branchiopods and the malacostracans. Food particles are then passed anteriorly along a ventral groove, leading to the mouthparts.[4]

    References

    1. ^ Howard L. Sanders (1955). "The Cephalocarida, a new subclass of Crustacea from Long Island Sound". Proceedings of the National Academy of Sciences. 41 (1): 61–66. Bibcode:1955PNAS...41...61S. doi:10.1073/pnas.41.1.61. JSTOR 89010. PMC 528024. PMID 16589618..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""'"'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
    2. ^ Boxshall, G. (2010). "Hutchinsoniellidae Sanders, 1955". World Register of Marine Species. Retrieved 2017-12-07.
    3. ^ a b Robert D. Barnes (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 672. ISBN 978-0-03-056747-6.
    4. ^ L. A. Zenkevich. "Phylum Arthropoda". The Animal Life [Zhizn' Zhivotnykh]. 2.

Morphology

    Morphology
    provided by Animal Diversity Web

    Other Physical Features: ectothermic ; bilateral symmetry