Insect: Difference between revisions

There are many different patterns of [[gas exchange]] demonstrated by different groups of insects. Gas exchange patterns in insects can range from continuous and [[diffusion|diffusive]] ventilation, to [[discontinuous gas exchange]].<ref name="Gullan and Cranston" />{{Rp|65–68}} During continuous gas exchange, [[oxygen]] is taken in and [[carbon dioxide]] is released in a continuous cycle. In discontinuous gas exchange, however, the insect takes in oxygen while it is active and small amounts of carbon dioxide are released when the insect is at rest.<ref name="IPE">{{cite book | last = Chown | first = S.L. |author2=S.W. Nicholson | title = Insect Physiological Ecology | publisher = Oxford University Press | year = 2004 | location = New York|isbn=978-0-19-851549-4}}</ref> Diffusive ventilation is simply a form of continuous gas exchange that occurs by [[diffusion]] rather than physically taking in the oxygen. Some species of insect that are submerged also have adaptations to aid in respiration. As larvae, many insects have gills that can extract oxygen dissolved in water, while others need to rise to the water surface to replenish air supplies, which may be held or trapped in special structures.<ref name="aquins" /><ref>{{cite book|author1=Merritt, RW |author2=KW Cummins |author3=MB Berg |last-author-amp=yes |title=An Introduction To The Aquatic Insects Of North America|year=2007|publisher=Kendall Hunt Publishing Company|isbn=978-0-7575-4128-5}}</ref>

 

Because oxygen is delivered directly to tissues via tracheoles, the circulatory system is not used to carry oxygen, and is therefore greatly reduced. The insect circulatory system is open; it has no [[vein]]s or [[artery|arteries]], and instead consists of little more than a single, perforated dorsal tube that pulses [[peristalsis|peristaltically]]. This dorsal blood vessel (element 14) is divided into two sections: the heart and aorta. The dorsal blood vessel circulates the [[hemolymph]], arthropods' fluid analog of [[blood]], from the rear of the body cavity forward.<ref name="Gullan and Cranston" />{{Rp|61–65}}<ref>{{cite web|url=http://www.cals.ncsu.edu/course/ent425/tutorial/circulatory.html|title=Circulatory System|last=Meyer|first=John R.|date=17 February 2006|publisher=Department of Entomology, NC State University|location=NC State University|page=1|archiveurl=https://web.archive.org/web/20090927000720/http://www.cals.ncsu.edu/course/ent425/tutorial/circulatory.html|archivedate=27 September 2009|deadurl=yes|accessdate=11 October 2009|df=dmy-all}}</ref> Hemolymph is composed of plasma in which [[hemocytes]] are suspended. Nutrients, hormones, wastes, and other substances are transported throughout the insect body in the hemolymph. Hemocytes include many types of cells that are important for immune responses, wound healing, and other functions. Hemolymph pressure may be increased by muscle contractions or by swallowing air into the digestive system to aid in moulting.<ref>{{Cite book|title=Borror and DeLong's introduction to the study of insects|last=Triplehorn|first=Charles|publisher=Thompson Brooks/Cole|others=Johnson, Norman F., Borror, Donald J.|year=2005|isbn=978-0030968358|edition= 7th|location=Belmont, CA|pages=27–28|oclc=55793895}}</ref> Hemolymph is also a major part of the open [[circulatory system]] of other [[arthropods]], such as [[spiders]] and [[crustaceans]].<ref>{{cite book|url=|title=The Insects; Structure and Function|last=Chapman|first=R. F.|date=1998|publisher=Cambridge University Press|isbn=978-0521578905|edition= 4th|series=|volume=|location=Cambridge, UK|pages=|doi=|jfm=|mr=|zbl=|id=}}</ref><ref>{{Cite journal|last1=Wyatt|first1=G.R.|year=1961|title=The Biochemistry of Insect Hemolymph|journal=Annual Review of Entomology|volume=6|pages=75–102|doi=10.1146/annurev.en.06.010161.000451|pmc=|pmid=}}</ref>