{{short description|Mode of invertebrate growth}} '''Neosomy''' is the formation of new external structure in an active stage of an invertebrate, in a taxon that normally only changes during moulting. It occurs in nematodes and a wide range of arthropods, especially those with symbiotic lifestyles.<ref name=":0">{{Cite journal |last1=Audy |first1=J. Ralph |last2=Radovsky |first2=F. J. |last3=Vercammen-Grandjean |first3=P. H. |date=1972-12-20 |title=Neosomy: Radical Intrastadial Metamorphosis Associated With Arthropod Symbioses |url=https://academic.oup.com/jme/article-lookup/doi/10.1093/jmedent/9.6.487 |journal=Journal of Medical Entomology |language=en |volume=9 |issue=6 |pages=487–494 |doi=10.1093/jmedent/9.6.487 |pmid=4654678 |issn=1938-2928|url-access=subscription }}</ref>
An organism that has undergone neosomy is a '''neosome''', while a new external structure formed by neosomy is a '''neosomule'''.<ref name=":0" />
Neosomy is similar to physogastrism (or physogastry) and the two phenomena are sometimes confused. However, physogastrism is usually defined as distension of the abdomen, without the growth of new cuticle.<ref>{{Citation |last=Radovsky |first=Frank J. |title=Neosomy |date=2009 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780123741448001867 |encyclopedia=Encyclopedia of Insects |pages=685–686 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-374144-8.00186-7 |isbn=978-0-12-374144-8 |access-date=2023-01-27|url-access=subscription }}</ref>
== Examples ==
=== Acari === thumb|An unfed and a fed ixodid tick Larvae of some chiggers can increase in size massively via neosomy, such as ''Vatacarus'' (from sea kraits) enlarging by 1500 times or more, and ''Riedlinia'' (from bats) by up to 750 times.<ref name=":0" />
Other mites with neosomatic larvae include ''Trombidium'', ''Eutrombidium'' and the aquatic ''Eylais'' and ''Hydrachna''.<ref>{{Citation |last1=Wohltmann |first1=Andreas |title=Acari: Terrestrial Parasitengona inhabiting transient biotopes |date=2006 |url=http://link.springer.com/10.1007/978-3-662-55958-1_6 |work=Süßwasserfauna von Mitteleuropa, Vol. 7/2-1 Chelicerata: Araneae/Acari I |pages=158–240 |editor-last=Gerecke |editor-first=Reinhard |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |language=de |doi=10.1007/978-3-662-55958-1_6 |isbn=978-3-662-55957-4 |access-date=2023-01-26 |last2=Gabryś |first2=Grzegorz |last3=Mąkol |first3=Joanna|url-access=subscription }}</ref>
In mites of family Hypoderatidae, deutonymphs grow by neosomy. Deutonymph are the main (sometimes only) feeding stage in the hypoderatid life cycle.<ref>{{Cite journal |last1=Mironov |first1=Sergey V. |last2=Ramilo |first2=David W.R. |date=2019-06-30 |title=A new mite species of the genus Neottialges (Acariformes: Hypoderatidae) from the black stork Ciconia nigra (Ciconiiformes: Ciconiidae) in Portugal |url=https://www1.montpellier.inrae.fr/CBGP/acarologia/article.php?id=4332 |journal=Acarologia |volume=59 |issue=2 |pages=279–287 |doi=10.24349/acarologia/20194332}}</ref>
In ticks of family Ixodidae, the larvae, nymphs and adult females show neosomy. This involves an initial period where the tick thickens its cuticle and slowly gains weight, then a rapid engorgement (increasing the tick's size by as much as 100 times) that returns the cuticle to its original thickness. In the soft ticks (Argasidae), neosomy usually occurs in larvae only.<ref name=":0" />
=== Insects === Females of some flea species in superfamilies Pulicoidea, Vermipsylloidea and Malacopsylloidea are neosomatic. For example, an adult female ''Tunga monositus'' starts out at 1 mm long and, after feeding and growing, increases in volume by 1000 times, becomes circular in shape and forms anterior lobes that the head is retracted between (for protection).<ref>{{Cite journal |last=Rothschild |first=Miriam |date=1992 |title=Neosomy in fleas, and the sessile life-style |journal=Journal of Zoology |volume=226 |issue=4 |pages=613–629 |doi=10.1111/j.1469-7998.1992.tb07504.x |issn=0952-8369}}</ref>
Similar to the aforementioned fleas, bat flies of genus ''Ascodipteron'' have females which attach to a host, then lose their limbs and transform into neosomes, with the head and thorax withdrawn into a swollen abdomen.<ref>{{Cite journal |last1=Sun |first1=Haoran |last2=Ding |first2=Liang |last3=Yan |first3=Liping |last4=Pape |first4=Thomas |last5=Zhang |first5=Dong |date=2021-04-23 |title=Ascodipteron sanmingensis sp. nov., a new bat fly (Hippoboscidae: streblid grade) from Fujian, China |journal=Biodiversity Data Journal |volume=9 |article-number=e64558 |doi=10.3897/BDJ.9.e64558 |issn=1314-2828 |pmc=8087615 |pmid=33948101 |doi-access=free }}</ref> thumb|Neosomatic termite queen Neosomy occurs in queen termites and in queen ants of certain species. Queen termites include the largest neosomes among terrestrial arthropods, with some exceeding 12.5 cm in length.<ref name=":0" />
Termite-associated species of phorid flies and rove beetles have neosomatic females. In rove beetles, some genera have neosomatic males as well as females, and neosomy in some genera results in an abdomen that resembles a termite.<ref name=":0" />
=== Crustaceans === Parasitic copepods, such as ''Lernaea'', ''Collipravus'', and ''Lernaeenicus'', exhibit neosomy. In some of the more extreme instances, neosomes vary greatly in shape within a species.<ref name=":0" />
== Purposes == Neosomy is a mechanism that allows a symbiote to better exploit abundant food. It increases the reproductive potential of females. For example, a female ixodid tick can usually lay thousands of eggs at once, compared to the few hundred eggs of a female non-neosomatic argasid.<ref name=":0" />
There are also other possible purposes. In ''Termitomimus'' and ''Nasutimimus'' rove beetles, the abdomen is similar in shape to a termite nymph and may be used in tactile mimicry.<ref>{{Cite journal |last=Kistner |first=David H. |date=1968 |title=Revision of the African Species of the Termitophilous Tribe Corotocini (Coleoptera, Staphylinidae) II. The Genera Termitomimus Tragardh and Nasutimimus New Genus and Their Relationships |journal=The Coleopterists Bulletin |volume=22 |issue=3 |pages=65–93 |doi=10.5962/p.372415 |jstor=3999251 |issn=0010-065X|doi-access=free }}</ref>
== References == <references />
Category:Animal developmental biology