| 词条 | Notostraca |
| 释义 |
| name = Notostraca | image = Triops australiensis.JPG | image_caption = Triops australiensis | image2 = LepidurusApus.jpg | image2_caption = Lepidurus apus | fossil_range = {{fossil range|Carboniferous|Recent}} | regnum = Animalia | phylum = Arthropoda | subphylum = Crustacea | classis = Branchiopoda | subclassis = Phyllopoda | ordo = Notostraca | ordo_authority = G. O. Sars, 1867 | familia = Triopsidae | familia_authority = Keilhack, 1909 | subdivision_ranks = Genera | subdivision =
}} The order Notostraca comprises the single family Triopsidae, containing the tadpole shrimp[1] or shield shrimp.[1] The two genera, Triops and Lepidurus, are considered living fossils, having not changed significantly in outward form since the Triassic. They have a broad, flat carapace, which conceals the head and bears a single pair of compound eyes. The abdomen is long, appears to be segmented and bears numerous pairs of flattened legs. The telson is flanked by a pair of long, thin caudal rami. Phenotypic plasticity within taxa makes species-level identification difficult, and is further compounded by variation in the mode of reproduction. Notostracans are omnivores living on the bottom of temporary pools and shallow lakes. DescriptionNotostracans are {{convert|2|-|10|cm|1}} long, with a broad carapace at the front end, and a long, slender abdomen.[2] This gives them a similar overall shape to a tadpole, from which the common name tadpole shrimp derives.[2] The carapace is dorso-ventrally flattened, smooth, and bears no rostrum; it includes the head, and the two sessile compound eyes are located together on top of the head.[2] The two pairs of antennae are much reduced, with the second pair sometimes missing altogether.[1] The mouthparts comprise a pair of uniramous mandibles and no maxillipeds.[1] The trunk comprises a large number of "body rings", which appear to be body segments, but do not always reflect the underlying segmentation.[2] The first eleven body rings compose the thorax and bear one pair of legs each, the last of which also bears the genital opening.[2] In the female, it is modified to form a "brood pouch".[10] The first one or two pairs of legs differ from the remainder, and probably function as sensory organs.[3] The remaining segments form the abdomen. The number of body rings is variable both within and between species,[2] and the number of pairs of legs per body ring can rise as high as six.[13] The legs become progressively smaller along the abdomen,[3] with the last segments being legless.[2] The abdomen ends in a telson and a pair of long, thin, multi-articulate caudal rami.[4] The form of the telson varies between the two genera: in Lepidurus, a rounded projection extends between the caudal rami, while in Triops there is no such projection.[2] Life cycleWithin the Notostraca, and even within species, there is variation in the mode of reproduction, with some populations reproducing sexually, some showing self-fertilisation of females, and some showing a mix of the two.[2] The frequency of males in populations is therefore highly variable.[3] In sexual populations, the sperm leave the male's body through simple pores, there being no penis. The eggs are released by the female and then held in the cup-like brood pouch.[3] The eggs are retained by the female only for a short time before being laid,[13] and the larvae develop directly, without passing through a metamorphosis.[1] Ecology and distributionNotostracans are omnivorous, eating small animals such as fishes and fairy shrimp.[2] They are found worldwide in freshwater, brackish water or saline pools, as well as in shallow lakes, peat bogs and moorland.[1] In Californian rice paddies, the species Triops longicaudatus is considered a pest, because it stirs up sediment, preventing light from reaching the rice seedlings.[5] Evolution and fossil recordThe fossil record of Notostraca is extensive, occurring in a wide range of geological deposits, and reaching back to the Carboniferous.[6] The lack of major morphological change since {{Ma|250}} has led to Notostraca being described as a living fossil.[27] Kazacharthra, a group known only from Triassic and Jurassic fossils from Kazakhstan and Western China,[7] are closely related to notostracans, and may belong within the order Notostraca.[8] The "central autapomorphy" of the Notostraca is the abandonment of filter feeding in open water, and the development of a benthic lifestyle in muddy waters, taking up food from particles of sediment and preying on small animals.[9] A number of other characteristics are correlated with this change, including the increased size of the animal compared to its relatives, and the loss of the ability to hinge the carapace; although a central keel marks the former separation into two valves, the adductor muscle is missing.[9] Notostracans retain the plesiomorphic condition of having two separate compound eyes, which abut, but have not become united, as seen in other groups of Branchiopoda.[9] TaxonomyThe order Notostraca is composed of a single family, Triopsidae, and only two genera, Triops and Lepidurus.[27] The phenotypic plasticity shown by notostracan species make identification to the species level difficult.[11] Many putative species have been described based on morphological variation, such that by the 1950s, as many as 70 species were recognised.[11] Two important revisions – those of Linder in 1952[12] and Longhurst in 1955[13] – synonymised many taxa, and resulted in the recognition of only 11 species in the two genera. This taxonomy was accepted for decades,[11] "even attaining the status of dogma".[14] More recent studies, especially those employing molecular phylogenetics, have shown that the eleven currently recognised species conceal a greater number of reproductively isolated populations.[11] See also
References1. ^1 2 3 4 {{cite web |url=http://crustacea.net/crustace/www/notostra.htm |author=J. K. Lowry |work=Crustacea, the Higher Taxa: Description, Identification, and Information Retrieval |date=October 2, 1999 |title=Notostraca (Branchiopoda) |publisher= |accessdate=February 7, 2011}} 2. ^1 2 3 4 5 6 7 8 9 10 {{cite book |author=Denton Belk |chapter=Branchiopoda |editor1=Sol Felty Light |editor2=James T. Carlton |year=2007 |title=The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon |edition=4th |publisher=University of California Press |isbn=978-0-520-23939-5 |pages=414–417 |url=https://books.google.com/books?id=64jgZ1CfmB8C&pg=PA417}} 3. ^1 2 3 4 {{cite book |author=Douglas Grant Smith |year=2001 |title=Pennak's freshwater invertebrates of the United States: Porifera to Crustacea |edition=4th |publisher=John Wiley and Sons |isbn=978-0-471-35837-4 |url=https://books.google.com/books?id=GqIctb8IqPoC&pg=PA431}} 4. ^{{cite book |title=The Invertebrata |edition=4th |year=1961 |publisher=Cambridge University Press |chapter=Subclass 1. Branchiopoda |pages=368–375 |url=https://books.google.com/books?id=7FM8AAAAIAAJ&pg=PA373}} 5. ^{{cite book |author=Hugh F. Clifford |year=1991 |title=Aquatic Invertebrates of Alberta: an Illustrated Guide |publisher=University of Alberta |isbn=978-0-88864-234-9 |chapter=Notostraca: tadpole shrimp |pages=144–145 |url=https://books.google.com/books?id=8UQ4jHev6voC&pg=PA144}} 6. ^{{cite book |author1=Atte Korhola |author2=Milla Rautio |lastauthoramp=yes |year=2001 |chapter=Cladocera and other branchiopod crustaceans |pages=5–41 |editor1=John P. Smol |editor2=Harry John Betteley Birks |editor3=William M. Last |title=Tracking Environmental Change Using Lake Sediments. Volume 4: Zoological Indicators |publisher=Kluwer Academic Publishers |isbn=978-1-4020-0658-6 |url=https://books.google.com/books?id=p-bwPq3P1YwC&pg=PA30}} 7. ^{{cite journal|last=Liu|first=Hongfu|journal=Acta Palaeontologica Sinica|year=1996|volume=4|issue=35|pages=490–494|url=http://europepmc.org/abstract/CBA/295478/reload=0;jsessionid=ZLmTAb0szp8TXnYtpqjL.4|title=New materials of Late Triassic Kazacharthra from Xinjaing}} 8. ^{{cite book |author=Marjorie L. Reaka-Kudla |year=2002 |chapter=Habitat specialization and its relation to conservation policy in Crustacea |pages=211–221 |editor=Elva Escobar-Briones & Fernando Alvarez |title=Modern Approaches to the Study of Crustacea |publisher=Springer |isbn=978-0-306-47366-1}} 9. ^1 2 3 4 {{cite book |author=Peter Ax |year=2000 |title=Multicellular Animals. The Phylogenetic System of the Metazoa. Volume II |publisher=Springer |isbn=978-3-540-67406-1|chapter=Notostraca |pages=158–159 |url=https://books.google.com/books?id=FweHI7uZ198C&pg=PA158}} 10. ^{{cite book |author=D. R. Khanna |year=2004 |title=Biology of Arthropoda |publisher=Discovery Publishing House |isbn=978-81-7141-897-8 |chapter=Segmentation in arthropods |pages=316–394 |url=https://books.google.com/books?id=Hd4OEDo4gbwC&pg=PA349}} 11. ^1 2 3 4 5 {{cite journal |author=Luc Brendonck, D. Christopher Rogers, Jorgen Olesen, Stephen Weeks & Walter R. Hoch |year=2008 |chapter=Global diversity of large branchiopods (Crustacea: Branchiopoda) in freshwater |journal=Hydrobiologia |volume=595 |issue=1 |pages=167–176 |doi=10.1007/s10750-007-9119-9 |title=Freshwater Animal Diversity Assessment |editor1=Estelle V. Balian |editor2=Christian Lévêque |editor3=Hendrik Segers |editor4=Koen Martens |series=Developments in Hydrobiology 198 |isbn=978-1-4020-8258-0}} 12. ^{{cite journal |author=Folke Linder |year=1952 |title=Contributions to the morphology and taxonomy of the Branchiopoda Notostraca, with special reference to the North American species |journal=Proceedings of the United States National Museum |volume=102 |issue=3291 |pages=1–69 |url=http://biostor.org/reference/3963 |doi=10.5479/si.00963801.102-3291.1}} 13. ^{{cite journal |author=Alan R. Longhurst |year=1955 |title=A review of the Notostraca |journal=Bulletin of the British Museum (Natural History) |volume=3 |issue=1 |pages=1–57 |url=http://biostor.org/reference/1299}} 14. ^{{cite journal |author=Clay Sassaman, Marie A. Simovich & Michael Fugate |year=1997 |title=Reproductive isolation and genetic differentiation in North American species of Triops (Crustacea: Branchiopoda: Notostraca) |journal=Hydrobiologia |volume=359 |issue=1–3 |pages=125–147 |doi=10.1023/A:1003168416080}} External links{{Commons category}}
23 : Notostraca|Living fossils|Freshwater crustaceans|Extant Carboniferous first appearances|Pennsylvanian taxonomic orders|Cisuralian taxonomic orders|Guadalupian taxonomic orders|Lopingian taxonomic orders|Early Triassic taxonomic orders|Middle Triassic taxonomic orders|Late Triassic taxonomic orders|Early Jurassic taxonomic orders|Middle Jurassic taxonomic orders|Late Jurassic taxonomic orders|Early Cretaceous taxonomic orders|Late Cretaceous taxonomic orders|Paleocene taxonomic orders|Eocene taxonomic orders|Oligocene taxonomic orders|Miocene taxonomic orders|Pliocene taxonomic orders|Pleistocene taxonomic orders|Holocene taxonomic orders |
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