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279:, appearing as pages in a book, are where gas exchange takes place. These appendages move rhythmically to drive blood in and out of the lamellae and to circulate water over them. Respiration being their main purpose, they can also be used for swimming in young individuals. If they are kept moist, the horseshoe crab can live on land for many hours.
275:) which have five pairs of them, the flap in front of them being the genital operculum which lacks gills. Book gills are flap-like appendages that effect gas exchange within water and seem to have their origin as modified legs. On the inside of each appendage, over 100 thin page-like membranes,
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Tetrapulmonata have two pairs of book lungs found on the second and third abdominal segments (Schizomida have lost a pair, and most advanced spiders have replaced at least one of the pairs with trachea). Scorpions have four pairs of book lungs, found on abdominal segments number three, four, five,
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One of the long-running controversies in arachnid evolution is whether the book lung evolved from book gills just once in a common arachnid ancestor, or whether book lungs evolved separately in several groups of arachnids as they came onto land. While the third abdominal segment in
Tetrapulmonata
258:. Although they have a similar book-like structure, book gills are external, while book lungs are internal. Both are considered appendages rather than conventional internal organs, as they develop from limb buds before the buds flatten into segmented
128:, have no traces of book lungs and breathe through tracheae or through their body-surfaces only. Gas exchange is performed by the thin walls inside the cavity instead, with their surface area increased by branching into the body as thin tubes called
20:
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Scholtz, Gerhard; Kamenz, Carsten (2006). "The book lungs of
Scorpiones and Tetrapulmonata (Chelicerata, Arachnida): Evidence for homology and a single terrestrialisation event of a common arachnid ancestor".
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Their number varies from just one pair in most spiders to four pairs in scorpions. The unfolded "pages" (plates) of the book lung are filled with hemolymph. The folds maximize the surface exposed to
63:. Each of these organs is located inside an open ventral abdominal, air-filled cavity (atrium) and connects with its surroundings through a small opening for the purpose of
132:. These tracheae may possibly have evolved directly from book lungs because the tracheae in some spiders have a small number of greatly elongated chambers.
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exchanged with the environment. In most species, no motion of the plates is needed to facilitate this kind of respiration.
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fossil lungs are almost indistinguishable from the lungs of modern arachnids, fully adapted to a terrestrial existence.
492:"Patterning mechanisms and morphological diversity of spider appendages and their importance for spider evolution"
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The pulmonate arachnids also appears to be the only members of
Arachnida where the respiratory pigment
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Pechmann, Matthias; Khadjeh, Sara; Sprenger, Frederik; Prpic, Nikola-Michael (November 2010).
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The origins of tetrapulmonate book lungs and their significance for chelicerate phylogeny
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have book lungs, the scorpions have a pair of sensory organs called pectines instead.
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Kamenz, Carsten; Dunlop, Jason A.; Scholtz, Gerhard; Kerp, Hans; Hass, Hagen (2008).
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The absence or presence of book lungs divides the
Arachnida into two main groups:
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In this spider diagram, the position of the book lungs is labelled 1.
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Internal anatomy of a female spider, book lungs shown in pink
93:. Stacks of alternating air pockets and tissue filled with
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used for atmospheric gas exchange that is present in many
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The oldest book lungs have been recovered from extinct
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The diversity and evolution of chelicerate hemocyanins
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Book gills are still present in the marine arthropod
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arachnids preserved in the 410 million-year-old
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give them an appearance similar to a "folded" book.
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250:Book lungs are thought to have evolved from book
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416:"Microanatomy of early Devonian book lungs"
254:, water-breathing structures among marine
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426:(2). London, UK: Royal Society: 212–215.
16:Type of lung commonly found in arachnids
463:Bhamrah, H. S.; Juneja, Kavita (2002).
328:. Oxford University Press US. pp.
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496:Arthropod Structure & Development
104:, and thereby maximize the amount of
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81:Book lungs are not related to the
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31:Spider book lungs (cross section)
547:Invertebrate respiratory system
469:. Anmol Publications Pvt. Ltd.
246:showing the legs and book gills
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466:An Introduction to Arthropoda
211:is present in their blood.
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393:10.1016/j.zool.2005.06.003
320:Foelix, Rainer F. (1996).
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173:The a-pulmonate arachnids
85:of modern land-dwelling
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432:10.1098/rsbl.2007.0597
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71:Structure and function
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75:Further information:
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301:equivalent of blood.
147:book lungs present;
91:convergent evolution
226:of Scotland. These
178:microwhip scorpions
176:book lungs absent;
112:Occasionally absent
324:Biology of Spiders
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136:Arachnid taxonomy
49:respiration organ
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387:(1): 2–13.
87:vertebrates
65:respiration
536:Categories
344:book lung.
308:References
234:Book gills
209:hemocyanin
198:sunspiders
182:harvestmen
157:Schizomida
126:harvestmen
120:, such as
55:, such as
521:20 August
299:arthropod
295:Hemolymph
283:Footnotes
204:and six.
194:Ricinulei
169:scorpions
161:Amblypygi
118:arachnids
95:hemolymph
57:scorpions
53:arachnids
45:book lung
516:20696272
450:18198139
401:16386884
277:lamellae
260:lamellae
228:Devonian
130:tracheae
441:2429929
381:Zoology
297:is the
268:Limulus
186:Acarina
165:spiders
61:spiders
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332:–64.
252:gills
122:mites
116:Many
83:lungs
523:2020
512:PMID
471:ISBN
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397:PMID
334:ISBN
124:and
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
