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| ==Description== | ==Description== | ||
| Palpigrades are tiny cousins of the ]s, or ]s, no more than {{convert|3|mm|in}} in length, and averaging {{convert|1|-|1.5|mm|2|abbr=on}}.<ref name="Ax">{{cite book |author=Peter Ax |year=2000 |title=Multicellular animals. The phylogenetic system of the Metazoa. Volume II |publisher=] |isbn= |
Palpigrades are tiny cousins of the ]s, or ]s, no more than {{convert|3|mm|in}} in length, and averaging {{convert|1|-|1.5|mm|2|abbr=on}}.<ref name="Ax">{{cite book |author=Peter Ax |year=2000 |title=Multicellular animals. The phylogenetic system of the Metazoa. Volume II |publisher=] |isbn=978-3-540-67406-1 |chapter=Palpigradi – Holotracheata |pages=120–121}}</ref> They have a thin, pale, segmented ], and a segmented abdomen that terminates in a whip-like flagellum. This is made up of 15 segment-like parts, or "articles", and may make up as much as half the animal's length.<ref name="Nardi"/> Each article of the flagellum bears ]s, giving the whole flagellum the appearanace of a ].<ref name="Nardi"/> The carapace is divided into two plates between the third and fourth leg pair of legs. They have no eyes. | ||
| As in some other arachnids, the first pair of legs are modified to serve as sensory organs, and are held clear of the ground while walking. Unusually, however, palpigrades use their ]s for locomotion, so that the animal appears to be walking on five pairs of legs.<ref name="Nardi">{{cite book |author=James B. Nardi |year=2007 |title=Life in the soil: a guide for naturalists and gardeners |series=Chicago Lectures in Mathematics Series |publisher=] |isbn= |
As in some other arachnids, the first pair of legs are modified to serve as sensory organs, and are held clear of the ground while walking. Unusually, however, palpigrades use their ]s for locomotion, so that the animal appears to be walking on five pairs of legs.<ref name="Nardi">{{cite book |author=James B. Nardi |year=2007 |title=Life in the soil: a guide for naturalists and gardeners |series=Chicago Lectures in Mathematics Series |publisher=] |isbn=978-0-226-56852-2}}</ref> | ||
| Some palpigrades have three pairs of abdominal lung-sacs, although these are not true ]s as there is no trace of the characteristic leaflike lamellae which defines book lungs. However, many species have no respiratory organs at all and breathe directly through the cuticle.<ref name=IZ>{{cite book |author= Barnes, Robert D. |year=1982 |title=Invertebrate Zoology |publisher= ] |location= Philadelphia, PA |page=614 |isbn=0-03-056747-5}}</ref> | Some palpigrades have three pairs of abdominal lung-sacs, although these are not true ]s as there is no trace of the characteristic leaflike lamellae which defines book lungs. However, many species have no respiratory organs at all and breathe directly through the cuticle.<ref name=IZ>{{cite book |author= Barnes, Robert D. |year=1982 |title=Invertebrate Zoology |publisher= ] |location= Philadelphia, PA |page=614 |isbn=0-03-056747-5}}</ref> | ||
| ==Ecology and behaviour== | ==Ecology and behaviour== | ||
| Species of Palpigradi live in interstitially in wet ] and ] soils.<ref name="Ax"/> A few species have been found in shallow coral sands and on tropical beaches.<ref name="Geire">{{cite book |author=Olav Geire |year=2009 |title=Meiobenthology: the microscopic motile fauna of aquatic sediments |publisher=] |isbn= |
Species of Palpigradi live in interstitially in wet ] and ] soils.<ref name="Ax"/> A few species have been found in shallow coral sands and on tropical beaches.<ref name="Geire">{{cite book |author=Olav Geire |year=2009 |title=Meiobenthology: the microscopic motile fauna of aquatic sediments |publisher=] |isbn=978-3-540-68657-6 |chapter=Palpigradi (Arachnidae) |pages=205–206}}</ref> They need a damp environment to survive, and they always hide from light, so they are commonly found in the moist earth under buried stones and rocks. They can be found on every continent, except in Arctic and Antarctic regions. Terrestrial Palpigradi have ] ]s, but littoral (beach-dwelling) species are able to pass through the water surface easily.<ref name="Geire"/> | ||
| Very little is known about palpigrade behaviour.<ref name="Nardi"/> They are believed to be predators like their larger relatives, feeding on minuscule animals in their habitat.<ref name="Nardi"/> Their mating habits are unknown, except that they lay only a few relatively large eggs at a time.<ref name="Nardi"/> | Very little is known about palpigrade behaviour.<ref name="Nardi"/> They are believed to be predators like their larger relatives, feeding on minuscule animals in their habitat.<ref name="Nardi"/> Their mating habits are unknown, except that they lay only a few relatively large eggs at a time.<ref name="Nardi"/> | ||
| ==Classification== | ==Classification== | ||
| By 2003, approximately 79 species of palpigrades had been described worldwide, in two families, containing a total of 7 genera.<ref>{{cite book |author=Mark S. Harvey |year=2003 |title=Catalogue of the smaller arachnid orders of the world: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae |publisher=] |isbn= |
By 2003, approximately 79 species of palpigrades had been described worldwide, in two families, containing a total of 7 genera.<ref>{{cite book |author=Mark S. Harvey |year=2003 |title=Catalogue of the smaller arachnid orders of the world: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae |publisher=] |isbn=978-0-643-06805-6 |chapter=Order Palpigradi Thorell |pages=151–174}}</ref> The two families are differentiated by the presence of ventral sacs on ]s IV–VI in ], and their absence in ].<ref>{{cite book |author=Joel Cracraft & Michael J. Donoghue |year=2004 |title=Assembling the tree of life |publisher=] |isbn=978-0-19-517234-8 |chapter=Palpigrades (Palpigradi) |pages=302}}</ref> | ||
| A single fossil palpigrade species has been described from the ] of ], which is probably of ] age.<ref>{{cite journal |author=J. Mark Rowland & W. David Sissom |year=1980 |title=Report on a fossil palpigrade from the Tertiary of Arizona, and a review of the morphology and systematics of the order (Arachnida: Palpigradida) |journal=] |volume=8 |pages=69–86 |url=http://www.jstor.org/stable/3705206}}</ref> Its familial position is uncertain. Older publications refer to a fossil palpigrade (or palpigrade-like animal) from the ] of the ] in Germany,<ref>Haase, E. 1890. Beitrag zur Kenntniss der fossilen Arachniden. ''Zeitschrift der Deutsche geologische Gesellschaft'', 1890: 629–657</ref> but this has now been shown to be a misidentified fossil insect.<ref>{{cite journal |author=Xavier Delclòs, André Nel, Dany Azar, Günter Bechly, Jason A. Dunlop, Michael S. Engel & Sam W. Heads |year=2008 |title=The enigmatic Mesozoic insect taxon Chresmodidae (Polyneoptera): New palaeobiological and phylogenetic data, with the description of a new species from the Lower Cretaceous of Brazil |journal=] |volume=247 |pages=353–381 |url=http://www.schweizerbart.de/resources/downloads/paper_previews/59265.pdf |format=] |doi=10.1127/0077-7749/2008/0247-0353}}</ref> | A single fossil palpigrade species has been described from the ] of ], which is probably of ] age.<ref>{{cite journal |author=J. Mark Rowland & W. David Sissom |year=1980 |title=Report on a fossil palpigrade from the Tertiary of Arizona, and a review of the morphology and systematics of the order (Arachnida: Palpigradida) |journal=] |volume=8 |pages=69–86 |url=http://www.jstor.org/stable/3705206}}</ref> Its familial position is uncertain. Older publications refer to a fossil palpigrade (or palpigrade-like animal) from the ] of the ] in Germany,<ref>Haase, E. 1890. Beitrag zur Kenntniss der fossilen Arachniden. ''Zeitschrift der Deutsche geologische Gesellschaft'', 1890: 629–657</ref> but this has now been shown to be a misidentified fossil insect.<ref>{{cite journal |author=Xavier Delclòs, André Nel, Dany Azar, Günter Bechly, Jason A. Dunlop, Michael S. Engel & Sam W. Heads |year=2008 |title=The enigmatic Mesozoic insect taxon Chresmodidae (Polyneoptera): New palaeobiological and phylogenetic data, with the description of a new species from the Lower Cretaceous of Brazil |journal=] |volume=247 |pages=353–381 |url=http://www.schweizerbart.de/resources/downloads/paper_previews/59265.pdf |format=] |doi=10.1127/0077-7749/2008/0247-0353}}</ref> | ||
Revision as of 01:13, 25 March 2012
| Palpigradi Temporal range: Pliocene–Recent PreꞒ Ꞓ O S D C P T J K Pg N | |
|---|---|
| File:Eukoenenia mirabilis.jpg | |
| Eukoenenia mirabilis | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Arachnida |
| Order: | Palpigradi Thorell, 1900 |
| Families & genera | |
| |
A palpigrade, commonly known as a microwhip scorpion, is an invertebrate animal belonging to the order Palpigradi in the class Arachnida, in the subphylum Chelicerata of the phylum Arthropoda.
Description
Palpigrades are tiny cousins of the uropygids, or whip scorpions, no more than 3 millimetres (0.12 in) in length, and averaging 1–1.5 mm (0.04–0.06 in). They have a thin, pale, segmented integument, and a segmented abdomen that terminates in a whip-like flagellum. This is made up of 15 segment-like parts, or "articles", and may make up as much as half the animal's length. Each article of the flagellum bears bristles, giving the whole flagellum the appearanace of a bottle brush. The carapace is divided into two plates between the third and fourth leg pair of legs. They have no eyes.
As in some other arachnids, the first pair of legs are modified to serve as sensory organs, and are held clear of the ground while walking. Unusually, however, palpigrades use their pedipalps for locomotion, so that the animal appears to be walking on five pairs of legs.
Some palpigrades have three pairs of abdominal lung-sacs, although these are not true book lungs as there is no trace of the characteristic leaflike lamellae which defines book lungs. However, many species have no respiratory organs at all and breathe directly through the cuticle.
Ecology and behaviour
Species of Palpigradi live in interstitially in wet tropical and subtropical soils. A few species have been found in shallow coral sands and on tropical beaches. They need a damp environment to survive, and they always hide from light, so they are commonly found in the moist earth under buried stones and rocks. They can be found on every continent, except in Arctic and Antarctic regions. Terrestrial Palpigradi have hydrophobic cuticles, but littoral (beach-dwelling) species are able to pass through the water surface easily.
Very little is known about palpigrade behaviour. They are believed to be predators like their larger relatives, feeding on minuscule animals in their habitat. Their mating habits are unknown, except that they lay only a few relatively large eggs at a time.
Classification
By 2003, approximately 79 species of palpigrades had been described worldwide, in two families, containing a total of 7 genera. The two families are differentiated by the presence of ventral sacs on sternites IV–VI in Prokoeneniidae, and their absence in Eukoeneniidae.
A single fossil palpigrade species has been described from the Onyx Marble of Arizona, which is probably of Pliocene age. Its familial position is uncertain. Older publications refer to a fossil palpigrade (or palpigrade-like animal) from the Jurassic of the Solnhofen limestone in Germany, but this has now been shown to be a misidentified fossil insect.
See also
References
- ^ Peter Ax (2000). "Palpigradi – Holotracheata". Multicellular animals. The phylogenetic system of the Metazoa. Volume II. Springer. pp. 120–121. ISBN 978-3-540-67406-1.
- ^ James B. Nardi (2007). Life in the soil: a guide for naturalists and gardeners. Chicago Lectures in Mathematics Series. University of Chicago Press. ISBN 978-0-226-56852-2.
- Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Saunders College. p. 614. ISBN 0-03-056747-5.
- ^ Olav Geire (2009). "Palpigradi (Arachnidae)". Meiobenthology: the microscopic motile fauna of aquatic sediments. Springer. pp. 205–206. ISBN 978-3-540-68657-6.
- Mark S. Harvey (2003). "Order Palpigradi Thorell". Catalogue of the smaller arachnid orders of the world: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae. CSIRO Publishing. pp. 151–174. ISBN 978-0-643-06805-6.
- Joel Cracraft & Michael J. Donoghue (2004). "Palpigrades (Palpigradi)". Assembling the tree of life. Oxford University Press. p. 302. ISBN 978-0-19-517234-8.
- J. Mark Rowland & W. David Sissom (1980). "Report on a fossil palpigrade from the Tertiary of Arizona, and a review of the morphology and systematics of the order (Arachnida: Palpigradida)". Journal of Arachnology. 8: 69–86.
- Haase, E. 1890. Beitrag zur Kenntniss der fossilen Arachniden. Zeitschrift der Deutsche geologische Gesellschaft, 1890: 629–657
- Xavier Delclòs, André Nel, Dany Azar, Günter Bechly, Jason A. Dunlop, Michael S. Engel & Sam W. Heads (2008). "The enigmatic Mesozoic insect taxon Chresmodidae (Polyneoptera): New palaeobiological and phylogenetic data, with the description of a new species from the Lower Cretaceous of Brazil" (PDF). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 247: 353–381. doi:10.1127/0077-7749/2008/0247-0353.
{{cite journal}}: CS1 maint: multiple names: authors list (link)