Editing Larva

{{Short description|Juvenile form of distinct animals before metamorphosis}}
{{Other uses}}
[[File:Papilio xuthus Larva 2011-10-15.jpg|thumb|250px|Larva of the ''[[Papilio xuthus]]'' [[butterfly]]]]
[[File:Eurosta solidaginis larva.jpg|thumb|''[[Eurosta solidaginis]]'' goldenrod gall fly larva]]

A '''larva''' ({{IPAc-en|'|l|ɑr|v|ə|}}; {{plural form}}: '''larvae''' {{IPAc-en|'|l|ɑr|v|iː|}}) is a distinct juvenile form many  [[animal]]s undergo before [[metamorphosis]] into their next life stage. Animals with indirect [[developmental biology|development]] such as [[insect]]s, some [[arachnid]]s, [[amphibian]]s, or [[cnidaria]]ns typically have a larval phase of their [[Biological life cycle|life cycle]].

A larva's appearance is generally very different from the adult form (''e.g.'' [[caterpillar]]s and [[butterfly|butterflies]]) including different unique structures and organs that do not occur in the adult form. Their diet may also be considerably different. In the case of smaller primitive arachnids, the larval stage differs by having three instead of four pairs of legs.<ref>{{cite web|url= https://dec.alaska.gov/eh/vet/ticks/tick-identification/#:~:text=Additionally%2C%20ticks%20go%20through%20three,of%20a%20grain%20of%20sand. | title= TICK IDENTIFICATION | date= 4 October 2024|work=Division of environmental health}}</ref>

Larvae are frequently adapted to different environments than adults. For example, some larvae such as [[tadpole]]s live almost exclusively in aquatic environments, but can live outside water as adult [[frog]]s. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population.

Animals in the larval stage will consume food to fuel their transition into the adult form. In some organisms like [[polychaete]]s and [[barnacle]]s, adults are immobile but their larvae are mobile, and use their mobile larval form to distribute themselves.<ref>{{Citation|last=Qian|first=Pei-Yuan|title=Larval settlement of polychaetes|date=1999|work=Reproductive Strategies and Developmental Patterns in Annelids|pages=239–253|place=Dordrecht|publisher=Springer Netherlands|doi=10.1007/978-94-017-2887-4_14|isbn=978-90-481-5340-4}}</ref><ref>{{Cite journal|last1=Chen|first1=Zhang-Fan|last2=Zhang|first2=Huoming|last3=Wang|first3=Hao|last4=Matsumura|first4=Kiyotaka|last5=Wong|first5=Yue Him|last6=Ravasi|first6=Timothy|last7=Qian|first7=Pei-Yuan|date=2014-02-13 |title=Quantitative Proteomics Study of Larval Settlement in the Barnacle Balanus amphitrite |journal=PLOS ONE |language=en |volume=9 |issue=2 |pages=e88744 |doi=10.1371/journal.pone.0088744 |pmid=24551147 |pmc=3923807|bibcode=2014PLoSO...988744C|issn=1932-6203 |doi-access=free}}</ref> These larvae used for dispersal are either [[Marine larval ecology#Larval development strategies|planktotrophic (feeding) or lecithotrophic (non-feeding)]].

Some larvae are dependent on adults to feed them. In many eusocial [[Hymenoptera]] species, the larvae are fed by female workers. In ''[[Ropalidia marginata]]'' (a paper wasp) the males are also capable of feeding larvae but they are much less efficient, spending more time and getting less food to the larvae.<ref>{{cite journal|last1=Sen|first1=R|last2=Gadagkar|first2=R|title=Males of the social wasp Ropalidia marginata can feed larvae, given an opportunity|journal=Animal Behaviour|date=2006|volume=71|issue=2|pages=345–350|doi=10.1016/j.anbehav.2005.04.022|s2cid=39848913}}</ref>

The larvae of some organisms (for example, some [[newt]]s) can become [[puberty|pubescent]] and do not develop further into the adult form. This is a type of [[neoteny]].<ref>{{Cite journal|last=Wakahara|first=Masami|date=1996|title=Heterochrony and Neotenic Salamanders: Possible Clues for Understanding the Animal Development and Evolution|journal=Zoological Science|volume=13|issue=6|pages=765–776|doi=10.2108/zsj.13.765|doi-broken-date=1 November 2024 |pmid=9107136|s2cid=35101681|issn=0289-0003}}</ref>

It is a misunderstanding that the larval form always [[Recapitulation theory|reflects the group's evolutionary history]]. This could be the case, but often the larval stage has evolved secondarily, as in insects.<ref>{{Citation|last1=Nagy|first1=Lisa M.|title=Cell Lineages in Larval Development and Evolutions of Holometabolous Insects|date=1999|work=The Origin and Evolution of Larval Forms|pages=275–300|publisher=Elsevier|isbn=978-0-12-730935-4|last2=Grbić|first2=Miodrag|doi=10.1016/b978-012730935-4/50010-9}}</ref><ref>{{Cite journal|last=Raff|first=Rudolf A|date=2008-01-11|title=Origins of the other metazoan body plans: the evolution of larval forms|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|volume=363|issue=1496|pages=1473–1479|doi=10.1098/rstb.2007.2237|pmid=18192188|issn=0962-8436|pmc=2614227}}</ref> In these cases{{clarify|reason=Please specify  in which of the two types of cases|date=February 2024}}, the larval form may differ more than the adult form from the group's common origins.<ref>{{cite journal |last1=Williamson |first1=Donald I. |author-link=Donald I. Williamson|date=2006 |title=Hybridization in the evolution of animal form and life-cycle |journal=Zoological Journal of the Linnean Society |volume=148 |issue= 4|pages=585–602 |doi= 10.1111/j.1096-3642.2006.00236.x|doi-access=free }}</ref>

==Selected types of larvae==
{| class="wikitable sortable"
! Animal || Name of larvae
|-
| [[Porifera]] (sponges) || coeloblastula (= blastula, amphiblastula), parenchymula (= [[parenchymella]], stereogastrula)
|-
| [[Rhombozoa|Heterocyemida]] || Wagener's larva
|-
| [[Dicyemida]] || infusoriform larva
|-
| [[Cnidarian]]s || [[planula]] (= stereogastrula), actinula
|-
| [[Ctenophora]] || cydippid larvae
|-
| [[Platyhelminthes]] || [[Turbellaria]]: [[Müller's larva]], Götte's larva;<br /> [[Trematoda]]: [[miracidium]], [[Trematode lifecycle stages|sporocyst]], [[Trematode lifecycle stages|redia]], [[cercaria]];<br /> [[Monogenea]]: [[oncomiracidium]];<br /> [[Cestoda]]: [[Cysticercosis|cysticercus]], [[cysticercoid]], [[oncosphere]] (or [[hexacanth]]), [[coracidium]], [[plerocercoid]]
|-
| [[Annelida]] || [[nectochaete]], polytroch
|-
| [[Nematoda]] || [[Dauer larva]], [[microfilaria]]
|-
| [[Sipuncula]] || pelagosphera larva
|-
| [[Ectoprocta]] || [[cyphonautes]], vesiculariform larvae
|-
| [[Nematomorpha]] || nematomorphan larva
|-
| [[Phoronid]]s || actinotroch 
|-
| [[Cycliophora]] || pandora, chordoid larva
|-
| [[Nemertea]] || pilidium, Iwata larva, Desor larva
|-
| [[Acanthocephala]] || acanthor
|-
| [[Locifera]] || Higgins larva
|-
| [[Brachiopoda]] || lobate larva
|-
| [[Priapula]] || loricate larva
|-
| Certain [[Mollusca|molluscs]], [[annelid]]s, [[nemertean]]s and [[sipunculid]]s || [[trochophore]]
|-
| Certain [[Mollusca|molluscs]] || [[veliger]]
|-
| [[Mollusca]]: freshwater [[Bivalvia]] (mussels) || [[glochidium]]
|-
| [[Arthropoda]]: †[[Trilobita]] || protaspis (unjointed), meraspis (increasing number of joints, but 1 less than the holaspis), holaspis (=adult)<ref name='Treatise'>{{cite book|last= Moore|first= R.C.|year= 1959|title= Arthropoda I – Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha|publisher= Geological Society of America/University of Kansas Press|series= [[Treatise on Invertebrate Paleontology]]|volume= Part O.|pages= O121, O122, O125|location= Boulder, Colorado/Lawrence, Kansas|isbn= 978-0-8137-3015-8}}</ref>
|-
| [[Arthropoda]]: [[Xiphosura]] || euproöps larva ("trilobite larva")
|-
| [[Arthropoda]]: [[Pycnogonida]] || protonymphon
|-
| [[Crustacean]]s || General: [[Crustacean larvae|nauplius, metanauplius, protozoea, antizoea, pseudozoea, zoea, postlarva, cypris, primary larva, mysis]]<br /> [[Decapoda]]: [[zoea]]<br /> [[Rhizocephala]]: [[kentrogon]]
|-
| [[Insect]]a: [[Lepidoptera]] (butterflies and moths) || [[caterpillar]]
|-
| [[Insect]]a: [[Beetle]]s || [[Beetle#Life cycle|grub]]
|-
| [[Insect]]a: [[Fly|Flies]], [[Bee]]s, [[Wasp]]s || [[maggot]]
|-
| [[Insect]]a: [[Mosquito]]es || [[Wriggler (mosquito larva)|wriggler]]
|-
| [[Insect]]a: [[Orthoptera]] (crickets and grasshoppers), [[Odonata]] (dragonflies and damselflies), [[Hemiptera]] (true bugs) || [[Nymph (biology)|nymph]]
|-
| [[Deuterostome]]s || [[dipleurula]] (hypothetical larva)
|-
| [[Echinodermata]] || [[bipinnaria]], vitellaria, brachiollaria, pluteus, ophiopluteus, echinopluteus, auricularia
|-
| [[Hemichordata]] || [[tornaria]]
|-
| [[Urochordata]] || tadpole (does not feed, technically a "swimming embryo")
|-
| [[Fish]] (generally) || [[Fish larva|Ichthyoplankton]]
|-
| [[Fish]]: [[Petromyzontiformes]] (lamprey) || [[ammocoete]]
|-
| [[Fish]]: [[Anguilliformes]] (eels) || [[leptocephalus]]
|-
| [[Amphibian]]s || [[Tadpole|tadpole, polliwog]]
|-
|}

==Insect larvae==
[[File:Hercules beetle (larva).jpg|thumb|The larvae of the [[Hercules beetle]] (''Dynastes hercules'') are among the largest of any species of insect]]
[[File:Micromus.aphids.2.jpg|thumb|Campodeiform larva of ''[[Micromus]]'' sp.]]

Within [[Insects]], only [[Endopterygota|Endopterygote]]s show complete metamorphosis, including a distinct larval stage.<ref>{{Cite web|title=Division: Endopterygota – Amateur Entomologists' Society (AES)|url=https://www.amentsoc.org/insects/fact-files/orders/endopterygota.html |access-date=2020-08-03|website=www.amentsoc.org}}</ref><ref>{{cite web |url=https://entomology.ca.uky.edu/ef017 |title=Recognizing Insect Larval Types |publisher=University of Kentucky |access-date=28 April 2016}}</ref> Several classifications have been suggested by many [[Entomology|entomologists]],<ref>{{Cite book|last=JOHNSON, NORMAN. TRIPLEHORN, CHARLES A.|title=BORROR AND DELONG'S INTRODUCTION TO THE STUDY OF INSECTS.|date=2020|publisher=CENGAGE LEARNING CUSTOM P|isbn=978-0-357-67127-6|oclc=1163940863}}</ref><ref>{{Cite book|title=Encyclopedia of Entomology|date=2008|publisher=Springer Netherlands|isbn=978-1-4020-6242-1|editor-last=Capinera|editor-first=John L.|location=Dordrecht|doi=10.1007/978-1-4020-6359-6}}</ref> and following classification is based on [[Antonio Berlese]] classification in 1913. There are four main types of endopterygote larvae types:<ref>{{cite web |url=http://www.agriinfo.in/default.aspx?page=topic&superid=6&topicid=1552 |title=Types of Insect Larva |publisher=Agri info |access-date=28 April 2016 | archive-url=https://web.archive.org/web/20160514042749/http://www.agriinfo.in/default.aspx?page=topic&superid=6&topicid=1552 |archive-date=14 May 2016 |url-status=dead }}</ref><ref>{{Cite web|date=2017-03-23|title=Types of Insect Larva|url=https://agriinfo.in/types-of-insect-larva-1531/|access-date=2021-11-22|website=agriinfo.in|language=en-US|archive-date=2017-02-04|archive-url=https://web.archive.org/web/20170204080237/http://www.agriinfo.in/default.aspx?page=topic&superid=6&topicid=1552|url-status=dead}}</ref>

# '''Apodous larvae''' – no legs at all and are poorly sclerotized. Based on [[Sclerotin|sclerotization]]. All Apocrita are apodous.  Three [[apodous]] forms are recognized.
#* Eucephalous – with well sclerotized head capsule. Found in [[Nematocera]], [[Buprestidae]] and [[Cerambycidae]] families.
#* Hemicephalus – with a reduced head capsule, retractable in to the thorax. Found in [[Tipulidae]] and [[Brachycera]] families. 
#* Acephalus – without head capsule. Found in [[Cyclorrhapha]]
# '''Protopod larvae''' – larva have many different forms and often unlike a normal insect form. They hatch from eggs which contain very little [[yolk]]. E.g. first [[instar]] larvae of parasitic hymenoptera.
# '''Polypod larvae''' – also known as '''eruciform larvae''', these larvae have abdominal prolegs, in addition to usual thoracic legs. They are poorly sclerotized and relatively inactive. They live in close contact with their food. Best example is [[caterpillar]]s of lepidopterans.
# '''Oligopod larvae''' – have well-developed head capsule and mouthparts are similar to the adult, but without compound eyes. They have six legs. No abdominal prolegs. Two types can be seen:
#* Campodeiform – well sclerotized, dorso-ventrally flattened body. Usually long legged predators with [[Prognathism|prognathous]] mouthparts. (lacewing, trichopterans, mayflies and some coleopterans).
#* Scarabeiform – poorly sclerotized, flat thorax and abdomen. Usually short legged and inactive burrowing forms. ([[Scarabaeoidea]] and other coleopterans).

==See also==
* [[Crustacean larvae]]
* [[Ichthyoplankton]]
* [[Maggots]]
* [[Spawn (biology)]]
* Non-larval animal [[Juvenile (organism)|juvenile]] (immature) stages and other [[biological life cycle|life cycle]] stages:
** In [[Porifera]]: olynthus, [[gemmule]]
** In [[Cnidaria]]: [[Jellyfish#Phases|ephyra]], scyphistoma, [[Strobilation|strobila]], [[gonangium]], hydranth, [[polyp (zoology)|polyp]], [[Medusa (biology)|medusa]]
** In [[Mollusca]]: [[paralarva]], young [[cephalopods]]
** In [[Platyhelminthes]]: [[hydatid cyst]]
** In [[Bryozoa]]: [[avicularium]]
** In [[Acanthocephala]]: cystacanth
** In [[Insecta]]: 
*** [[Nymph (biology)|Nymphs and naiads]], immature forms in [[hemimetabolism|hemimetabolous]] insects
*** [[Subimago]], a juvenile that resembles the adult in [[Ephemeroptera]]
*** [[Instar]], intermediate between each [[ecdysis]]
*** [[Pupa]] and [[chrysalis]], intermediate stages between larva and [[imago]] (the adult stage)
* Protozoan life cycle stages
** [[Apicomplexan life cycle]]
* Algal life cycle stages:
** ''[[Codiolum]]''-phase
** ''[[Red algae|Conchocelis]]''-phase
* [[Marine larval ecology]]

==References==
{{Reflist}}

==Bibliography==
* Brusca, R. C. & Brusca, G. J. (2003). ''Invertebrates'' (2nd ed.). Sunderland, Mass. : Sinauer Associates.
* Hall, B. K. & Wake, M. H., eds. (1999). ''The Origin and Evolution of Larval Forms''. San Diego: Academic Press.
* Leis, J. M. & Carson-Ewart, B. M., eds. (2000). The Larvae of Indo-Pacific Coastal Fishes. An Identification Guide to Marine Fish Larvae''. Fauna Malesiana handbooks, vol. 2. Brill, Leiden. 
* Minelli, A. (2009). The larva. In: ''Perspectives in Animal Phylogeny and Evolution''. Oxford University Press. p. 160–170. [https://books.google.com/books?id=jIASDAAAQBAJ link].
* Shanks, A. L. (2001). ''An Identification Guide to the Larval Marine Invertebrates of the Pacific Northwest''. Oregon State University Press, Corvallis. 256 pp. 
* Smith, D. & Johnson, K. B. (1977). ''A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae''. Kendall/Hunt Plublishing Company.
* Stanwell-Smith, D., Hood, A. & Peck, L. S. (1997). ''A field guide to the pelagic invertebrates larvae of the maritime Antarctic''. British Antarctic Survey, Cambridge.
* Thyssen, P.J. (2010). [https://www.springer.com/cda/content/document/cda_downloaddocument/9781402096839-c2.pdf?SGWID=0-0-45-1118144-p173877432 Keys for Identification of Immature Insects] {{Webarchive|url=https://web.archive.org/web/20170809221659/https://www.springer.com/cda/content/document/cda_downloaddocument/9781402096839-c2.pdf?SGWID=0-0-45-1118144-p173877432 |date=2017-08-09 }}. In: Amendt, J. et al. (ed.). ''Current Concepts in Forensic Entomology'', chapter 2, pp.&nbsp;25–42. Springer: Dordrecht.

== External links ==
{{EB1911 Poster|Larval Forms}}
{{Commons category}}
{{wiktionary}}
*[http://rstb.royalsocietypublishing.org/content/365/1540/653.full Arenas-Mena, C. (2010) Indirect development, transdifferentiation and the macroregulatory evolution of metazoans. Philosophical Transactions of the Royal Society B: Biological Sciences. Feb 27, 2010 Vol.365 no.1540 653–669]

{{Authority control}}

[[Category:Larvae| ]]
[[Category:Insect developmental biology]]