View source for Invertebrate

{{Short description|Animals without a vertebral column}}
{{pp-vandalism|small=yes}}
{{Paraphyletic group
| name = Invertebrates
| fossil_range = [[Cryogenian]] to [[Holocene|Present]], {{Long fossil range|665|0}}
| image = Invertebrate montage (2022).jpg
| image_upright = 1.2
| image_alt = Diversity of various invertebrates from different phyla (including a invertebrate of the phylum Chordata)
| image_caption = '''Left to right''': ''[[Chrysaora fuscescens]]'' ([[Cnidaria]]), ''[[Fromia indica]]'' ([[Echinodermata]]), [[Caribbean reef squid]] ([[Mollusca]]), ''[[Drosophila melanogaster]]'' ([[Arthropoda]]), ''[[Aplysina|Aplysina lacunosa]]'' ([[Porifera]]), ''[[Pseudobiceros hancockanus]]'' ([[Platyhelminthes]]), ''[[Hirudo medicinalis]]'' ([[Annelida]]), ''[[Polycarpa aurata]]'' ([[Tunicata]]), ''[[Milnesium tardigradum]]'' ([[Tardigrada]]).
| auto = yes
| parent = Animalia
| includes = *All animal groups not in subphylum [[Vertebrata]]
}}
'''Invertebrates''' are [[animal]]s that neither develop nor retain a [[vertebral column]] (commonly known as a ''spine'' or ''backbone''), which evolved from the [[notochord]]. It is a [[paraphyletic]] grouping including all animals excluding the [[chordata|chordate]] [[subphylum]] [[Vertebrata]], i.e. [[vertebrate]]s. Well-known [[Phylum|phyla]] of invertebrates include [[arthropod]]s, [[mollusc]]s, [[annelid]]s, [[echinoderm]]s, [[flatworm]]s, [[cnidarian]]s, and [[sponge]]s.

The majority of animal species are invertebrates; one estimate puts the figure at 97%.<ref>{{cite journal|first=Robert M.|last=May|date=16 September 1988|title=How Many Species Are There on Earth?|journal=Science|volume=241|issue=4872|pages=1441–9|url=http://www.ciesin.org/docs/002-253/002-253.html|jstor=1702670|pmid=17790039|doi=10.1126/science.241.4872.1441|bibcode=1988Sci...241.1441M|s2cid=34992724|access-date=17 June 2014|archive-url=https://web.archive.org/web/20161115011411/http://www.ciesin.org/docs/002-253/002-253.html|archive-date=15 November 2016|url-status=dead|url-access=subscription}}</ref>  Many invertebrate [[taxon|taxa]] have a greater number and diversity of species than the entire subphylum of Vertebrata.<ref name="isbn0-412-61390-5">{{cite book |author1=Richards, O. W. |author2=Davies, R.G. |title=Imms' General Textbook of Entomology: Volume 1: Structure, Physiology and Development Volume 2: Classification and Biology |publisher=Springer |location=Berlin |year=1977 |isbn=978-0-412-61390-6 }}</ref> Invertebrates vary widely in size, from 10&nbsp;[[Micrometre|μm]] (0.0004&nbsp;in)<ref>{{cite book |last1=Canning |first1=Elizabeth U. |last2=Okamura |first2=Beth |chapter=Biodiversity and Evolution of the Myxozoa |date=2003-01-01 |title=Advances in Parasitology |volume=56 |pages=43–131 |publisher=Academic Press |doi=10.1016/S0065-308X(03)56002-X |pmid=14710996 |isbn=978-0-12-031756-1}}</ref> [[myxozoa]]ns to the 9–10 m (30–33&nbsp;ft) [[colossal squid]].<ref>Roper, C.F.E. & P. Jereb (2010). Family Cranchiidae. In: P. Jereb & C.F.E. Roper (eds.) ''[http://www.fao.org/docrep/014/i1920e/i1920e00.htm Cephalopods of the world. An annotated and illustrated catalogue of species known to date. Volume 2. Myopsid and Oegopsid Squids] {{Webarchive|url=https://web.archive.org/web/20190129054613/http://www.fao.org/docrep/014/i1920e/i1920e00.htm |date=29 January 2019 }}''. FAO Species Catalogue for Fishery Purposes No. 4, Vol. 2. FAO, Rome. pp.&nbsp;148–178.</ref>

Some so-called invertebrates, such as the [[Tunicata]] and [[Cephalochordata]], are actually sister chordate subphyla to Vertebrata, being more closely related to vertebrates than to other invertebrates. This makes the "invertebrates" [[paraphyletic]], so the term has no significance in [[taxonomy (biology)|taxonomy]].

== Etymology ==

The word "invertebrate" comes from the Latin word {{wikt-lang|la|vertebra}}, which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. The jointed aspect of ''vertebra'' is derived from the concept of turning, expressed in the root ''verto'' or ''vorto'', to turn.<ref name="Latin Tucker">{{cite dictionary |last=Tucker |first=T. G. |entry=Vertebra |title=A Concise Etymological Dictionary of Latin |publisher=Max Niemeyer Verlag |location=Halle (Saale) |year=1931 }}</ref> The prefix ''in-'' means "not" or "without".<ref>{{cite book |last=Skeat |first=Walter William |title=An etymological dictionary of the English language |url=https://archive.org/details/anetymologicald02skeagoog |year=1882 |publisher=Clarendon Press |page=301}}</ref>

== Taxonomic significance ==

The term ''invertebrates'' does not describe a [[taxon]] in the same way that [[Arthropod]]a, [[Vertebrata]] or [[Manidae]] do. Each of those terms describes a valid taxon,  [[phylum]], [[subphylum]] or [[Family (biology)|family]]. "Invertebrata" is a term of convenience, not a taxon; it has very little [[Circumscription (taxonomy)|circumscriptional]] significance except within the [[Chordate|Chordata]]. The Vertebrata as a [[Taxonomic rank|subphylum]] comprises such a small proportion of the [[Animal|Metazoa]] that to speak of the [[Kingdom (biology)|kingdom]] [[Animal]]ia in terms of "Vertebrata" and "Invertebrata" has limited practicality. In the more formal taxonomy of Animalia other attributes that logically should precede the presence or absence of the vertebral column in constructing a [[cladogram]], for example, the presence of a [[notochord]]. That would at least circumscribe the Chordata. However, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry<ref name=" Pech">{{cite book | last = Pechenik | first = Jan | title = Biology of the Invertebrates | publisher = Wm. C. Brown Publishers | location = Dubuque | year = 1996 | isbn = 978-0-697-13712-8 }}</ref> or perhaps [[Body plan|Bauplan]].<ref>{{cite book |last1=Brusca |first1=Richard C. |last2=Brusca |first2=Gary J. | title = Invertebrates |url=https://archive.org/details/invertebrates0000brus  |url-access=registration  | publisher = Sinauer Associates | location = Sunderland | year = 1990 | isbn = 978-0-87893-098-2 }}</ref>

Despite this, the concept of ''invertebrates'' as a taxon of animals has persisted for over a century among the [[laity]],<ref name="isbn0-19-861271-0">{{cite book |author=Brown, Lesley |title=The New shorter Oxford English dictionary on historical principles |publisher=Clarendon |location=Oxford [Eng.] |year=1993 |isbn=978-0-19-861271-1 |url=https://archive.org/details/newshorteroxford00lesl }}</ref> and within the zoological community and in its literature it remains in use as a term of convenience for animals that are not members of the Vertebrata.<ref name="Agassiz2013">{{cite book |first=Louis |last=Agassiz |title=Essay on Classification |url=https://books.google.com/books?id=O6fDAgAAQBAJ&pg=PT115 |date=21 March 2013 |publisher=Courier Corporation |isbn=978-0-486-15135-9 |pages=115–}}</ref> The following text reflects earlier scientific understanding of the term and of those animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone, either internal or external. They include hugely varied [[body plan]]s. Many have fluid-filled, hydrostatic skeletons, like [[jellyfish]] or worms. Others have hard [[exoskeleton]]s, outer shells like those of [[insect]]s and [[crustacean]]s. The most familiar invertebrates include the [[Protozoa]], [[Porifera]], [[Coelenterata]], [[Platyhelminthes]], [[Nematoda]], [[Annelida]], [[Echinodermata]], [[Mollusca]] and [[Arthropoda]]. Arthropoda include [[insect]]s, [[crustacean]]s and [[arachnid]]s.

== Number of extant species ==

By far the largest number of described invertebrate species are insects. The following table lists the number of described [[Extant taxa|extant]] species for major invertebrate groups as estimated in the [[IUCN Red List of Threatened Species]], 2014.3.<ref name=IUCN1014>The World Conservation Union. 2014. ''[[IUCN Red List of Threatened Species]]'', 2014.3. Summary Statistics for Globally Threatened Species. [http://cmsdocs.s3.amazonaws.com/summarystats/2014_3_Summary_Stats_Page_Documents/2014_3_RL_Stats_Table_1.pdf Table 1: Numbers of threatened species by major groups of organisms (1996–2014)] {{Webarchive|url=https://web.archive.org/web/20150224091921/http://cmsdocs.s3.amazonaws.com/summarystats/2014_3_Summary_Stats_Page_Documents/2014_3_RL_Stats_Table_1.pdf |date=24 February 2015 }}.</ref>

{| class="wikitable sortable"
|-
! Invertebrate group
! Phylum
! Image
! Estimated number of<br />described species<ref name=IUCN1014 />
|-
| [[Insects]]
| [[Arthropoda]]
| [[File:European wasp white bg02.jpg|100px]] 
| align=right | 1,000,000
|-
| [[Arachnids]]
| [[Arthropoda]]
| [[File:PlatycryptusUndatusFemale.jpg|100px]]
| align=right | 102,248
|-
| [[Gastropod]]s
| [[Mollusca]]
| [[File:Grapevinesnail 01.jpg|100px]] 
| align=right | 85,000
|-
| [[Crustacean]]s
| [[Arthropoda]]
| [[File:J J Wild Pseudocarcinus cropped.jpg|100px]]
| align=right | 47,000
|-
| [[Bivalve]]s
| [[Mollusca]]
| [[File:Argopecten_irradians.jpg|100px]] 
| align=right | 20,000
|-
| [[Anthozoa|Sea anemones,<br/>corals, sea pens]]
| [[Cnidaria]]
| [[File:Coral_Outcrop_Flynn_Reef.jpg|100px]] 
| align=right | 2,175
|-
| [[Cephalopod]]s
| [[Mollusca]]
| [[File:Sepia_officinalis1.jpg|100px]] 
| align=right | 900
|-
| [[Velvet worms]]
| [[Onychophora]]
| [[File:Velvet worm.jpg|100px]] 
| align=right | 165
|-
| [[Horseshoe crabs]]
| [[Arthropoda]]
| [[File:Carcinoscorpius rotundicauda (mangrove horseshoe crab).jpg|100px]]
| align=right | 4
|-
| Others<br/><small>[[jellyfish]], [[echinoderm]]s,<br/>[[sponge]]s, etc.</small>
| —
| —
| align=right | 68,658
|-
|
|
! align=right | Total:
! align=right | ~1,300,000
|}

The [[IUCN]] estimates that 66,178 [[Vertebrate#Number of extant species|extant vertebrate species]] have been described,<ref name=IUCN1014 /> which means that over 95% of the described animal species in the world are invertebrates.

== Characteristics ==

The trait that is common to all invertebrates is the absence of a [[vertebral column]] (backbone): this creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only; it is not based on any clear biologically [[Homology (biology)|homologous]] trait, any more than the common trait of having wings functionally unites insects, bats, and birds, or than not having wings unites [[tortoise]]s, [[snail]]s and [[sponge]]s. Being animals, invertebrates are heterotrophs, and require sustenance in the form of the consumption of other organisms. With a few exceptions, such as the [[Porifera]], invertebrates generally have bodies composed of differentiated tissues. There is also typically a digestive chamber with one or two openings to the exterior.

=== Morphology and symmetry ===

The [[body plan]]s of most [[multicellular organism]]s exhibit some form of [[Symmetry in biology|symmetry]], whether radial, bilateral, or spherical. A minority, however, exhibit no symmetry. One example of asymmetric invertebrates includes all [[gastropod]] species. This is easily seen in [[snail]]s and [[sea snail]]s, which have helical shells. [[Slug]]s appear externally symmetrical, but their [[pneumostome]] (breathing hole) is located on the right side. Other gastropods develop external asymmetry, such as ''[[Glaucus atlanticus]]'' that develops asymmetrical [[cerata]] as they mature. The origin of gastropod asymmetry is a subject of scientific debate.<ref name="gastropod development">{{cite journal| author=Louise R. Page| title=Modern insights on gastropod development: Reevaluation of the evolution of a novel body plan| journal=Integrative and Comparative Biology| year=2006| volume=46| issue=2| pages=134–143| doi=10.1093/icb/icj018| pmid=21672730| df=dmy-all| doi-access=free}}</ref>

Other examples of asymmetry are found in [[fiddler crab]]s and [[hermit crab]]s. They often have one claw much larger than the other. If a male fiddler loses its large claw, it will grow another on the opposite side after [[moulting]]. [[Sessility (zoology)|Sessile]] animals such as [[sponge]]s are asymmetrical<ref name=Columbia>[http://www.factmonster.com/ce6/sci/A0847482.html Symmetry, biological] {{Webarchive|url=https://web.archive.org/web/20121113143415/http://www.factmonster.com/ce6/sci/A0847482.html |date=13 November 2012 }}, cited at FactMonster.com from ''[[The Columbia Electronic Encyclopedia]]'' (2007).</ref> alongside [[coral]] [[Colony (biology)|colonies]] (with the exception of the individual [[polyp (zoology)|polyp]]s that exhibit radial symmetry); [[Alpheidae]] claws that lack pincers; and some [[copepod]]s, [[polyopisthocotylea]]ns, and [[monogenea]]ns which parasitize by attachment or residency within the [[gill]] chamber of their [[fish]] [[host (biology)|hosts]]).

==== Nervous system ====

[[Neurons]] differ in invertebrates from mammalian cells. Invertebrates cells fire in response to similar stimuli as mammals, such as tissue trauma, high temperature, or changes in pH. The first invertebrate in which a neuron cell was identified was the medicinal [[leech]], ''[[Hirudo medicinalis]]''.<ref name="Nicholls and Baylor, 1968">{{cite journal |vauthors=Nicholls JG, Baylor DA |title=Specific modalities and receptive fields of sensory neurons in CNS of the leech |journal=Journal of Neurophysiology |volume=31 |issue=5 |pages=740–756 |date=September 1968 |pmid=5711143 |doi=10.1152/jn.1968.31.5.740 }}</ref><ref name="Pastor et al., 1996">{{cite journal |vauthors=Pastor J, Soria B, Belmonte C |title=Properties of the nociceptive neurons of the leech segmental ganglion |journal=Journal of Neurophysiology |volume=75 |issue=6 |pages=2268–2279 |date=June 1996 |pmid=8793740 |doi=10.1152/jn.1996.75.6.2268 }}</ref>
Learning and memory using nociceptors have been described in the sea hare, ''[[Aplysia]]''.<ref name="Byrne et al., 1978">{{cite journal |vauthors=Byrne JH, Castellucci VF, Kandel ER |title=Contribution of individual mechanoreceptor sensory neurons to defensive gill-withdrawal reflex in Aplysia |journal=Journal of Neurophysiology |volume=41 |issue=2 |pages=418–431 |date=March 1978 |pmid=650275 |doi=10.1152/jn.1978.41.2.418 }}</ref><ref name="Castellucci et al., 1970">{{cite journal |vauthors=Castellucci V, Pinsker H, Kupfermann I, Kandel ER |title=Neuronal mechanisms of habituation and dishabituation of the gill-withdrawal reflex in Aplysia |journal=Science |volume=167 |issue=3926 |pages=1745–1748 |date=March 1970 |pmid=5416543 |doi=10.1126/science.167.3926.1745 |bibcode=1970Sci...167.1745C }}</ref><ref name="Fischer et al., 2011">{{cite journal |vauthors=Fischer TM, Jacobson DA, Counsell AN, Pelot MA, Demorest K |title=Regulation of low-threshold afferent activity may contribute to short-term habituation in Aplysia californica |journal=Neurobiology of Learning and Memory |volume=95 |issue=3 |pages=248–259 |date=March 2011 |pmid=21144906 |doi=10.1016/j.nlm.2010.11.016 }}</ref> Mollusk neurons are able to detect increasing pressures and tissue trauma.<ref name="Illich and Walters, 1997">{{cite journal |vauthors=Illich PA, Walters ET |title=Mechanosensory neurons innervating Aplysia siphon encode noxious stimuli and display nociceptive sensitization |journal=Journal of Neuroscience |volume=17 |issue=1 |pages=459–469 |date=January 1997 |pmid=8987770 |pmc=6793714 |doi=10.1523/JNEUROSCI.17-01-00459.1997 }}Mechanosensory neurons innervating Aplysia siphon encode noxious stimuli and display nociceptive sensitization. The Journal of Neuroscience, 17: 459–469</ref>

Neurons have been identified in a wide range of invertebrate species, including annelids, molluscs, [[nematode]]s and arthropods.<ref name="Eismann et al., 1984">Eisemann, C.H., Jorgensen, W.K., Merritt, D.J., Rice, M.J., Cribb, B.W., Webb, P.D. and Zalucki, M.P., (1984). "Do insects feel pain? — A biological view". Cellular and Molecular Life Sciences, 40: 1420–1423</ref><ref name="St John Smith and Lewis, 2009">{{cite journal |vauthors=Smith ES, Lewin GR |title=Nociceptors: a phylogenetic view |journal=Journal of Comparative Physiology A |volume=195 |issue=12 |pages=1089–1106 |date=December 2009 |pmid=19830434 |pmc=2780683 |doi=10.1007/s00359-009-0482-z }}</ref>

====Respiratory system====

[[File:Tracheal system of dissected cockroach.tif|thumb|Tracheal system of dissected [[cockroach]].  The largest tracheae run across the width of the body of the cockroach and are horizontal in this image. Scale bar, 2 mm.]]
[[File:Cockroach tracheae supplying crop.tiff|thumb|The tracheal system branches into progressively smaller tubes, here supplying the [[Crop (anatomy)|crop]] of the cockroach.  Scale bar, 2.0 mm.]]

One type of invertebrate respiratory system is the open [[respiratory system]] composed of [[Spiracle (arthropods)|spiracles]], tracheae, and [[tracheole]]s that [[terrestrial animal|terrestrial]] arthropods have to transport [[metabolism|metabolic]] gases to and from tissues.<ref>Wasserthal, Lutz T. (1998). Chapter 25: The Open Hemolymph System of Holometabola and Its Relation to the Tracheal Space. In "Microscopic Anatomy of Invertebrates". Wiley-Liss, Inc. {{ISBN|0-471-15955-7}}.</ref>  The distribution of spiracles can vary greatly among the many [[order (biology)|orders]] of insects, but in general each segment of the body can have only one pair of spiracles, each of which connects to an atrium and has a relatively large tracheal tube behind it. The tracheae are invaginations of the cuticular [[exoskeleton]] that branch ([[anastomosis|anastomose]]) throughout the body with diameters from only a few micrometres up to 0.8&nbsp;mm. The smallest tubes, tracheoles, penetrate cells and serve as sites of [[diffusion]] for [[water]], [[oxygen]], and [[carbon dioxide]]. Gas may be conducted through the respiratory system by  means of active [[Ventilation (physiology)|ventilation]] or passive diffusion. Unlike vertebrates, insects do not generally carry oxygen in their [[hemolymph|haemolymph]].<ref>{{cite journal |author1=Westneat, Mark W. |author2=Betz, Oliver |author3=Blob, Richard W. |author4=Fezzaa, Kamel |author5=Cooper, James W. |author6=Lee, Wah-Keat |title=Tracheal Respiration in Insects Visualized with Synchrotron X-ray Imaging |journal=Science |date=January 2003 |volume=299 |pages=558–560 |doi=10.1126/science.1078008 |pmid=12543973 |issue=5606 |bibcode=2003Sci...299..558W |s2cid=43634044 }}{{Dead link|date=December 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

A tracheal tube may contain ridge-like circumferential rings of [[taenidia]] in various [[geometry|geometries]] such as loops or [[helix|helices]]. In the [[Cephalon (arthropod head)|head]], [[Thorax (arthropod anatomy)|thorax]], or [[Abdomen#Arthropoda|abdomen]], tracheae may also be connected to air sacs. Many insects, such as [[grasshopper]]s and [[bee]]s, which actively pump the air sacs in their abdomen, are able to control the flow of air through their body. In some aquatic insects, the tracheae exchange gas through the body wall directly, in the form of a [[gill]], or function essentially as normal, via a [[Plastron (arthropod)|plastron]]. Despite being internal, the tracheae of arthropods are shed during moulting ([[ecdysis]]).<ref>{{Cite journal|last=Ewer|first=John|date=2005-10-11|title=How the Ecdysozoan Changed Its Coat|journal=PLOS Biology|volume=3|issue=10|pages=e349|doi=10.1371/journal.pbio.0030349|pmid=16207077|pmc=1250302|issn=1545-7885 |doi-access=free }}</ref>

==== Hearing ====

{{excerpt|Ear|Invertebrates}}

=== Reproduction ===

Like vertebrates, most invertebrates reproduce at least partly through [[sexual reproduction]]. They produce specialized [[Gametogonium|reproductive cells]] that undergo [[meiosis]] to produce smaller, motile [[spermatozoon|spermatozoa]] or larger, non-motile [[ovum|ova]].<ref>{{cite book|last=Schwartz|first=Jill|title=Master the GED 2011 (w/CD)|year=2010|publisher=Peterson's|isbn=978-0-7689-2885-3|page=[https://archive.org/details/petersonsmasterg0000stew_x3f1/page/371 371]|url=https://archive.org/details/petersonsmasterg0000stew_x3f1/page/371}}</ref> These fuse to form [[zygote]]s, which develop into new individuals.<ref>{{cite book|last=Hamilton|first=Matthew B.|title=Population genetics|url=https://archive.org/details/populationgeneti00hami|url-access=limited|year=2009|publisher=Wiley-Blackwell|isbn=978-1-4051-3277-0|page=[https://archive.org/details/populationgeneti00hami/page/n69 55]}}</ref> Others are capable of [[asexual reproduction]], or sometimes, both methods of reproduction.

Extensive research with model invertebrate species such as ''[[Drosophila melanogaster]]'' and ''[[Caenorhabditis elegans]]'' has contributed much to our understanding of [[meiosis]] and reproduction. However, beyond the few model systems, the modes of reproduction found in invertebrates show incredible diversity.<ref name="Picard2021">{{cite journal |vauthors=Picard MA, Vicoso B, Bertrand S, Escriva H |title=Diversity of Modes of Reproduction and Sex Determination Systems in Invertebrates, and the Putative Contribution of Genetic Conflict |journal=Genes (Basel) |volume=12 |issue=8 |pages=1136 |date=July 2021 |pmid=34440310 |pmc=8391622 |doi=10.3390/genes12081136 |doi-access=free}}</ref>  In one extreme example, it is estimated that 10% of [[Oribatida|orbatid mite]] species have persisted without sexual reproduction and have reproduced asexually for more than 400 million years.<ref name = Picard2021/>

==== Reproductive systems ====
{{excerpt|Reproductive system|Invertebrates}}

===Social interaction===
Social behavior is widespread in invertebrates, including cockroaches, termites, aphids, [[thrips]], ants, bees, [[Passalidae]], [[Acari]], spiders, and more.<ref name=ChoeCrespi1997>{{cite book|title=The Evolution of Social Behavior in Insects and Arachnids|date=1997|publisher=Cambridge University Press|isbn=978-0521589772}}</ref> Social interaction is particularly salient in [[eusocial]] species but applies to other invertebrates as well.

Insects recognize information transmitted by other insects.<ref name="Riley">{{Cite journal| doi = 10.1038/nature03526| pmid = 15889092| year = 2005| last1 = Riley | first1 = J.| last2 = Greggers | first2 = U.| last3 = Smith | first3 = A.| last4 = Reynolds | first4 = D.| last5 = Menzel | first5 = R.| title = The flight paths of honeybees recruited by the waggle dance| volume = 435| issue = 7039| pages = 205–7| journal = Nature |bibcode = 2005Natur.435..205R | s2cid = 4413962}}</ref><ref>{{cite journal |author1=Seeley T.D. |author2=Visscher P.K. |author3=Passino K.M. | year = 2006 | title = Group decision making in honey bee swarms | journal = American Scientist | volume = 94 | issue = 3| pages = 220–9 | doi=10.1511/2006.3.220|doi-broken-date=1 July 2025 }}</ref><ref name="Frisch1967">Frisch, Karl von. (1967) The Dance Language and Orientation of Bees. Cambridge, Massachusetts: The Belknap Press of Harvard University Press.</ref>

=== Phyla ===

[[File:Cladocora.jpg|right|thumb|The fossil coral ''[[Cladocora]]'' from the [[Pliocene]] of [[Cyprus]]]]

The term invertebrates covers several phyla. One of these are the sponges ([[Porifera]]). They were long thought to have diverged from other animals early.<ref>{{cite book|title=An Introduction to Porifera|year=2003|publisher=Anmol Publications PVT. LTD.|isbn=978-81-261-0675-2|author=Bhamrah, H. S.|author2=Kavita Juneja|page=58}}</ref> They lack the complex organization found in most other phyla.<ref>{{cite book|last=Sumich|first=James L.|title=Laboratory and Field Investigations in Marine Life|year=2008|publisher=Jones & Bartlett Learning|isbn=978-0-7637-5730-4|page=67}}</ref> Their cells are differentiated, but in most cases not organized into distinct tissues.<ref>{{cite book|last=Jessop|first=Nancy Meyer|title=Biosphere; a study of life|year=1970|publisher=Prentice-Hall|page=428}}</ref> Sponges typically feed by drawing in water through pores.<ref>{{cite book|last=Sharma|first=N. S.|title=Continuity And Evolution Of Animals|year=2005|publisher=Mittal Publications|isbn=978-81-8293-018-6|page=106}}</ref> Some speculate that sponges are not so primitive, but may instead be secondarily simplified.<ref>{{Cite journal |last1=Dunn |first1=Casey W. |last2=Hejnol |first2=Andreas |last3=Matus |first3=David Q. |last4=Pang |first4=Kevin |last5=Browne |first5=William E. |last6=Smith |first6=Stephen A. |last7=Seaver |first7=Elaine |last8=Rouse |first8=Greg W. |last9=Obst |first9=Matthias |last10=Edgecombe |first10=Gregory D. |last11=Sørensen |first11=Martin V. |last12=Haddock |first12=Steven H. D. |last13=Schmidt-Rhaesa |first13=Andreas |last14=Okusu |first14=Akiko |last15=Kristensen |first15=Reinhardt Møbjerg |date=April 2008 |title=Broad phylogenomic sampling improves resolution of the animal tree of life |url=https://www.nature.com/articles/nature06614 |journal=Nature |language=en |volume=452 |issue=7188 |pages=745–9 |doi=10.1038/nature06614 |pmid=18322464 |bibcode=2008Natur.452..745D |issn=1476-4687|url-access=subscription }}</ref> The [[Ctenophora]] and the [[Cnidaria]], which includes [[sea anemone]]s, [[coral]]s, and [[jellyfish]], are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus.<ref>{{cite book|title=A living bay: the underwater world of Monterey Bay|year=2000|publisher=University of California Press|isbn=978-0-520-22149-9|author=Langstroth, Lovell|author2=Libby Langstroth|author3=Todd Newberry|author4=Monterey Bay Aquarium|page=[https://archive.org/details/livingbayunderwa0000lang/page/244 244]|url=https://archive.org/details/livingbayunderwa0000lang/page/244}}</ref> Both have distinct tissues, but they are not organized into [[organ (anatomy)|organs]].<ref>{{cite book|last=Safra|first=Jacob E.|title=The New Encyclopædia Britannica, Volume 16|year=2003|publisher=Encyclopædia Britannica|isbn=978-0-85229-961-6|page=523}}</ref> There are only two main germ layers, the [[ectoderm]] and [[endoderm]], with only scattered cells between them. As such, they are sometimes called [[diploblastic]].<ref>{{cite book|last=Kotpal|first=R. L.|title=Modern Text Book of Zoology: Invertebrates|publisher=Rastogi Publications|isbn=978-81-7133-903-7|page=184|year=2012}}</ref>

The [[Echinodermata]] are radially symmetric and exclusively marine, including [[starfish]] (Asteroidea), [[sea urchin]]s, (Echinoidea), [[brittle star]]s (Ophiuroidea), [[Holothuroidea|sea cucumbers]] (Holothuroidea) and [[Crinoid|feather stars]] (Crinoidea).<ref>{{cite book|last=Alcamo|first=Edward|title=Biology Coloring Workbook|year=1998|publisher=The Princeton Review|isbn=978-0-679-77884-4|page=220}}</ref>

The largest animal phylum is also included within invertebrates: the Arthropoda, including insects, [[spider]]s, [[crab]]s, and their kin. All these organisms have a body divided into repeating segments, typically with paired appendages. In addition, they possess a hardened exoskeleton that is periodically shed during growth.<ref name=forensic>{{cite book|last=Gunn|first=Alan|page=214|title=Essential forensic biology|publisher=John Wiley and Sons|year=2009|isbn=978-0-470-75804-5}}</ref> Two smaller phyla, the [[Onychophora]] and [[Tardigrada]], are close relatives of the arthropods and share some traits with them, excluding the hardened exoskeleton. The [[Nematoda]], or roundworms, are perhaps the second largest animal phylum, and are also invertebrates. Roundworms are typically microscopic, and occur in nearly every environment where there is water.<ref>{{cite book|title=BioInquiry: making connections in biology|year=2003|publisher=John Wiley|isbn=978-0-471-20228-8|author=Prewitt, Nancy L.|author2=Larry S. Underwood|author3=William Surver|page=[https://archive.org/details/bioinquiry00nanc_0/page/289 289]|url=https://archive.org/details/bioinquiry00nanc_0/page/289}}</ref> A number are important parasites.<ref>{{cite book|title=Parasites in social insects|year=1998|publisher=Princeton University Press|isbn=978-0-691-05924-2|last=Schmid-Hempel|first=Paul|page=75}}</ref> Smaller phyla related to them are the [[Kinorhyncha]], [[Priapulida]], and [[Loricifera]]. These groups have a reduced coelom, called a pseudocoelom. Other invertebrates include the [[Nemertea]], or ribbon worms, and the [[Sipuncula]].

Another phylum is [[Platyhelminthes]], the flatworms.<ref name=Gilson>{{cite book|last=Gilson|first=Étienne|title=El espíritu de la filosofía medieval|year=2004|publisher=Ediciones Rialp|isbn=978-84-321-3492-0|page=384}}</ref> These were originally considered primitive, but it now appears they developed from more complex ancestors.<ref>{{cite journal |last1=Ruiz-Trillo |first1=Iñaki |last2=Riutort |first2=Marta |last3=Littlewood |first3=D. Timothy J. |last4=Herniou |first4=Elisabeth A. |last5=Baguñà |first5=Jaume |date=March 1999 |title=Acoel Flatworms: Earliest Extant Bilaterian Metazoans, Not Members of Platyhelminthes |journal=Science |volume=283 |issue=5409 |pages=1919–23 |doi=10.1126/science.283.5409.1919 |pmid=10082465 |issn=0036-8075 |bibcode=1999Sci...283.1919R |s2cid=6079655 }}{{Dead link|date=December 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Flatworms are [[Coelom|acoelomates]], lacking a body cavity, as are their closest relatives, the microscopic [[Gastrotricha]].<ref name="umodena">{{cite web |url=http://www.gastrotricha.unimore.it/overview.htm |title=Gastrotricha: Overview |access-date=2008-01-26 |last=Todaro |first=Antonio |work=Gastrotricha: World Portal |publisher=University of Modena & Reggio Emilia |archive-date=2 October 2006 |archive-url=https://web.archive.org/web/20061002033954/http://www.gastrotricha.unimore.it/overview.htm |url-status=live }}</ref> The [[Rotifera]], or rotifers, are common in aqueous environments. Invertebrates also include the [[Acanthocephala]], or spiny-headed worms, the [[Gnathostomulida]], [[Micrognathozoa]], and the [[Cycliophora]].<ref name="IntroCyclio">{{cite journal |last=Kristensen |first= Reinhardt Møbjerg |date=July 2002 |title=An Introduction to Loricifera, Cycliophora, and Micrognathozoa |journal=Integrative and Comparative Biology |volume=42 |issue=3 |pages=641–651 |doi =10.1093/icb/42.3.641 |pmid=21708760|doi-access=free }}</ref>

Also included are two of the most successful animal phyla, the Mollusca and Annelida.<ref>{{cite web |url=http://www.lophelia.org/lophelia/biodiv_6.htm |title=Biodiversity: Mollusca|access-date=2007-11-19 |publisher=The Scottish Association for Marine Science |archive-url = https://web.archive.org/web/20060708083128/http://www.lophelia.org/lophelia/biodiv_6.htm |archive-date = 2006-07-08}}</ref><ref>{{cite video | people = Russell, Bruce J. (Writer), Denning, David (Writer) | title = Branches on the Tree of Life: Annelids| medium = [[VHS]] | publisher = BioMEDIA ASSOCIATES |date = 2000 }}</ref> The former, which is the second-largest animal phylum by number of described species, includes animals such as [[snail]]s, [[clam]]s, and [[squid]]s, and the latter comprises the segmented worms, such as [[earthworm]]s and [[leech]]es. These two groups have long been considered close relatives because of the common presence of [[trochophore]] larvae, but the annelids were considered closer to the arthropods because they are both segmented.<ref>{{cite journal|last1=Eernisse|first1=Douglas J. |last2=Albert|first2=James S. |last3=Anderson|first3=Frank E. | title=Annelida and Arthropoda are not sister taxa: A phylogenetic analysis of spiralean metazoan morphology | journal=Systematic Biology | volume=41 | issue=3 | pages = 305–330 | date=1 September 1992 | doi=10.2307/2992569 | issn=1063-5157| jstor=2992569 }}</ref> Now, this is generally considered [[convergent evolution]], owing to many morphological and genetic differences between the two phyla.<ref>{{cite journal|author=Eernisse, Douglas J. |author2=Kim, Chang Bae |author3=Moon, Seung Yeo |author4=Gelder, Stuart R. |author5=Kim, Won |title=Phylogenetic Relationships of Annelids, Molluscs, and Arthropods Evidenced from Molecules and Morphology |journal=Journal of Molecular Evolution |volume=43 |issue=3 |pages=207–215 |date=September 1996 |doi=10.1007/PL00006079 |pmid=8703086 |bibcode=1996JMolE..43..207K }}{{dead link|date=June 2016|bot=medic}}{{cbignore|bot=medic}}</ref>

Among lesser phyla of invertebrates are the [[Hemichordata]], or acorn worms,<ref>{{cite book|title=Asking about life|year=2005|publisher=Cengage Learning|isbn=978-0-534-40653-0|author=Tobin, Allan J.|author2=Jennie Dusheck|page=497}}</ref> and the Chaetognatha, or arrow worms. Other phyla include [[Acoelomorpha]], [[Brachiopoda]], [[Bryozoa]], [[Entoprocta]], [[Phoronida]], and [[Xenoturbellida]].

== Classification ==

Invertebrates can be classified into several main categories, some of which are [[Biological classification|taxonomically]] obsolescent or debatable, but still used as terms of convenience. Each however appears in its own article at the following links.<ref>{{cite web| url=https://www.reference.com/science/main-groups-invertebrates-30b0365b4702b5f8| title=What Are the Main Groups of Invertebrates?| date=4 August 2015| access-date=17 January 2019| archive-date=17 January 2019| archive-url=https://web.archive.org/web/20190117070101/https://www.reference.com/science/main-groups-invertebrates-30b0365b4702b5f8| url-status=live}}</ref>

* [[Sponges]] (Porifera)
* [[Comb jellies]] (Ctenophora)
* [[Cnidaria|Medusozoans and corals]] (Cnidaria)
* [[Xenacoelomorpha|Acoels]] (Xenacoelomorpha)
* [[Flatworm]]s (Platyhelminthes)
* [[Annelid|Bristleworms, earthworms and leeches]] (Annelida)
* [[Arthropod|Insects, springtails, crustaceans, myriapods, chelicerates]] (Arthropoda)
* [[Mollusca|Chitons, snails, slugs, bivalves, tusk shells, cephalopods]] (Mollusca)
* [[Nematodes|Roundworms or threadworms]] (Nematoda)
* [[Rotifers]] (Rotifera)
* [[Tardigrades]] (Tardigrada)
* [[Scalidophora|Scalidophores]] (Scalidophora)
* [[Lophophorata|Lophophorates]] (Lophophorata)
* [[Velvet worms]] (Onychophora)
* [[Arrow worms]] (Chaetognatha)
* [[Nematomorph|Gordian worms or horsehair worms]] (Nematomorpha)
* [[Nemertea|Ribbon worms]] (Nemertea)
* [[Placozoa]]
* [[Loricifera]]
* [[Echinoderm|Starfishes, sea urchins, sea cucumbers, sea lilies and brittle stars]] (Echinodermata)
* [[Hemichordata|Acorn worms, cephalodiscids and graptolites]] (Hemichordata)
* [[Amphioxiformes|Lancelets]] (Amphioxiformes)
* [[Tunicates|Salps, pyrosomes, doliolids, larvaceans and sea squirts]] (Tunicata)
* [[Symbion|Cycliophora]]

== History ==

The earliest animal fossils are of invertebrates. 665-million-year-old fossils in the Trezona Formation at Trezona Bore, West Central Flinders, South Australia have been interpreted as being early sponges.<ref name="roseMaloof">{{cite journal | author1= Maloof, Adam C. |author2= Rose, Catherine V. |author3= Beach, Robert |author4= Samuels, Bradley M. |author5= Calmet, Claire C. |author6= Erwin, Douglas H. |author7= Poirier, Gerald R. |author8= Yao, Nan |author9= Simons, Frederik J.|title= Possible animal-body fossils in pre-Marinoan limestones from South Australia |journal= Nature Geoscience | volume= 3 | page= 653 |date= 17 August 2010 |doi=10.1038/ngeo934 | issue= 9 | bibcode=2010NatGe...3..653M  }}</ref> Some paleontologists suggest that animals appeared much earlier, possibly as early as 1&nbsp;billion years ago<ref>{{cite book|title=Biology|year=2005|publisher=Pearson, Benjamin Cummings|isbn=978-0-8053-7171-0|author=Campbell. Neil A.|edition=7|author2=Jane B. Reece|page=526}}</ref> though they probably became multicellular in the [[Tonian]]. [[Trace fossil]]s such as tracks and burrows found in the late [[Neoproterozoic]] Era indicate the presence of [[triploblastic]] worms, roughly as large (about 5&nbsp;mm wide) and complex as [[earthworm]]s.<ref name="Seilacher1998">{{cite journal | title=Animals More Than 1 Billion Years Ago: Trace Fossil Evidence from India | journal=Science | volume=282 | pages=80–83 | date=October 1998 | last1=Seilacher|first1=A. | last2=Bose |first2=P.K. | last3=Pflüger |first3=F. | doi=10.1126/science.282.5386.80 | pmid=9756480 | issue=5386 |bibcode = 1998Sci...282...80S }}</ref>

Around 453 MYA, animals began diversifying, and many of the important groups of invertebrates diverged from one another. Fossils of invertebrates are found in various types of sediment from the [[Phanerozoic]].<ref name=clarkson>{{cite book |last=Clarkson |first=Euan Neilson Kerr |title=Invertebrate palaeontology and evolution |publisher=Wiley-Blackwell |isbn=978-0-632-05238-7 |year=1998}}</ref> Fossils of invertebrates are commonly used in stratigraphy.<ref name=Kummel>{{cite book |last=Kummel |first=Bernhard |title=Status of invertebrate paleontology, 1953 |page=93 |isbn=978-0-405-12715-1 |year=1954 |publisher=Ayer Publishing}}</ref>

=== Classification ===

[[Carl Linnaeus]] divided these animals into only two groups, the Insecta and the now-obsolete [[Vermes]] ([[worm]]s). [[Jean-Baptiste Lamarck]], who was appointed to the position of "Curator of Insecta and Vermes" at the [[Muséum National d'Histoire Naturelle]] in 1793, both coined the term "invertebrate" to describe such animals and divided the original two groups into ten, by splitting Arachnida and Crustacea from the Linnean Insecta, and Mollusca, Annelida, [[Barnacle|Cirripedia]], [[Radiata]], [[Coelenterata]] and [[Infusoria]] from the Linnean Vermes. They are now classified into over 30 [[phylum|phyla]], from simple organisms such as [[sea sponge]]s and [[flatworm]]s to complex animals such as arthropods and molluscs.

==== Significance ====

Invertebrates are animals without a vertebral column. This has led to the conclusion that ''in''vertebrates are a group that deviates from the normal, vertebrates. This has been said to be because researchers in the past, such as Lamarck, viewed vertebrates as a "standard": in Lamarck's theory of evolution, he believed that characteristics acquired through the evolutionary process involved not only survival, but also progression toward a "higher form", to which humans and vertebrates were closer than invertebrates were. Although goal-directed evolution has been abandoned, the distinction of invertebrates and vertebrates persists to this day, even though the grouping has been noted to be "hardly natural or even very sharp." Another reason cited for this continued distinction is that Lamarck created a precedent through his classifications which is now difficult to escape from. It is also possible that some humans believe that, they themselves being vertebrates, the group deserves more attention than invertebrates.<ref name=rskbarnes>{{cite book|last=Barnes|first=Richard Stephen Kent|title=The Invertebrates: A Synthesis|isbn=978-0-632-04761-1|publisher=Wiley-Blackwell|year=2001|page=3}}</ref> In any event, in the 1968 edition of ''Invertebrate Zoology'', it is noted that "division of the Animal Kingdom into vertebrates and invertebrates is artificial and reflects human bias in favor of man's own relatives." The book also points out that the group lumps a vast number of species together, so that no one characteristic describes all invertebrates. In addition, some species included are only remotely related to one another, with some more related to vertebrates than other invertebrates (see [[Paraphyly]]).<ref>{{Cite book|last=Barnes |first=Robert D.|year=1968|title=Invertebrate Zoology|edition=2nd|publisher=W.B. Saunders|oclc=173898}}</ref>

== In research ==

For many centuries, invertebrates were neglected by biologists, in favor of big vertebrates and "useful" or [[charismatic species]].<ref name="Aristotle"/> Invertebrate biology was not a major field of study until the work of [[Carl Linnaeus|Linnaeus]] and [[Lamarck]] in the 18th century.<ref name="Aristotle">{{cite web |url=http://nmnh.typepad.com/no_bones/2015/06/why-study-invertebrates-a-philosophical-argument-from-aristotle.html |title=Why study invertebrates? A philosophical argument from Aristotle |last1=Ducarme |first1=Frédéric |date=2015 |website=No Bones (Smithsonian Institution website) |access-date=15 July 2015 |archive-date=15 July 2015 |archive-url=https://web.archive.org/web/20150715175131/http://nmnh.typepad.com/no_bones/2015/06/why-study-invertebrates-a-philosophical-argument-from-aristotle.html |url-status=live }}</ref> During the 20th century, invertebrate zoology became one of the major fields of natural sciences, with prominent discoveries in the fields of medicine, genetics, palaeontology, and ecology.<ref name="Aristotle"/> The study of invertebrates has also benefited law enforcement, as arthropods, and especially insects, were discovered to be a source of information for forensic investigators.<ref name=forensic />

Two of the most commonly studied model organisms nowadays are invertebrates: the fruit fly ''[[Drosophila melanogaster]]'' and the nematode ''[[Caenorhabditis elegans]]''. They have long been the most intensively studied [[model organism]]s, and were among the first life-forms to be genetically sequenced. This was facilitated by the severely reduced state of their [[genome]]s, but many [[gene]]s, [[intron]]s, and [[genetic linkage|linkages]] have been lost. Analysis of the [[starlet sea anemone]] genome has emphasised the importance of sponges, placozoans, and [[choanoflagellate]]s, also being sequenced, in explaining the arrival of 1,500 ancestral genes unique to animals.<ref>{{cite journal |author=N.H. Putnam |date=July 2007 |title=Sea anemone genome reveals ancestral eumetazoan gene repertoire and genomic organization |journal=[[Science (journal)|Science]]|volume=31 |issue=5834 |pages=86–94 |doi=10.1126/science.1139158 |pmid=17615350|first1=N.H.|last2=Srivastava |first2=M.|last3=Hellsten |first3=U. |last4=Dirks |first4=B.|last5=Chapman|first5=J.|last6=Salamov |first6=A.|last7=Terry |first7=A.|last8=Shapiro |first8=H. |last9=Lindquist |first9=E.|last10=Kapitonov|first11=J.|last12=Genikhovich|first12=G. |last13=Grigoriev|first13=I.V. |last14=Lucas|first14=S.M.|last15=Steele |first15=R.E.|last16=Finnerty |first16=J.R.|last17=Technau |first17=U.|last18=Martindale |first18=M.Q.|last19=Rokhsar |first19=D.S. |first10=V. V. |last11=Jurka |bibcode=2007Sci...317...86P |osti=910591 |s2cid=9868191 |display-authors=3 |url=https://digital.library.unt.edu/ark:/67531/metadc884638/ |access-date=21 January 2019 |archive-date=1 August 2020 |archive-url=https://web.archive.org/web/20200801213038/https://digital.library.unt.edu/ark:/67531/metadc884638/ |url-status=live}}</ref> Invertebrates are also used by scientists in the field of [[aquatic biomonitoring]] to evaluate the effects of water pollution and [[climate change]].<ref>{{cite journal | last1=Lawrence|first1=J.E. |first2=K.B.|last2=Lunde |first3=R.D. |last3=Mazor |first4=L.A.|last4=Bêche |first5=E.P.|last5=McElravy |first6=V.H.|last6=Resh | title = Long-Term Macroinvertebrate Responses to Climate Change: Implications for Biological Assessment in Mediterranean-Climate Streams | journal = Journal of the North American Benthological Society | volume =29 | pages =1424–40 | year = 2010| doi= 10.1899/09-178.1 | issue =4 |s2cid=84679634 }}</ref>

== See also ==

* [[Invertebrate zoology]]
* [[Invertebrate paleontology]]
* [[Marine invertebrates]]
* [[Pain in invertebrates]]

==References==

{{Reflist}}

== Further reading ==
{{refbegin}}
* {{cite book |author-link=Libbie Hyman |first=L.H. |last=Hyman |title=The Invertebrates |publisher=McGraw-Hill |date=1940 |oclc=896702848 }} (6 volumes) A classic work.
* {{cite book |editor-first=D.T. |editor-last=Anderson |title=Invertebrate zoology |publisher=Oxford University Press |edition=2nd |date=2001 |isbn=978-0-19-551368-4 |oclc=48627623 }}
* {{cite book |last1=Brusca |first1=R.C. |last2=Brusca |first2=G.J. |title=Invertebrates |publisher=Sinauer Associates |edition=2nd |date=2003 |isbn=978-0-87893-097-5 |oclc=51053596 }}
* {{cite book |last1=Miller |first1=S.A. |last2=Harley |first2=J.P. |title=Zoology |publisher=WCB/McGraw-Hill |edition=4th |date=1996 |isbn=0-697-24374-5 |oclc=33263056 }}
* {{cite book |title=Biology of the invertebrates |last=Pechenik |first=Jan A. |year=2005 |publisher=McGraw-Hill, Higher Education |location=Boston |isbn=978-0-07-234899-6 |oclc=54805957 |edition=5th }}
* {{cite book |last1=Ruppert |first1=E.E. |last2=Fox |first2=R.S. |last3=Barnes |first3=R.D. |title=Invertebrate zoology: a functional evolutionary approach |publisher=Thomas-Brooks/Cole |location=Belmont CA |date=2004 |isbn=978-0-03-025982-1 |oclc=475257771 }}
* {{cite book |last1=Adiyodi |first1=K.G. |last2=Adyiodi |first2=R.G. |title=Reproductive Biology of Invertebrates |publisher=Wiley |orig-date=1983 |oclc=679323766 }} (Many volumes.)
* {{cite book |editor-last=Giese |editor-first=A.G. |editor2-last=Pearse |editor2-first=J.S. |title=Reproduction of Marine Invertebrates |publisher=Academic Press |orig-date=1974 |oclc=679395548 }} (Many volumes.)
* [https://www.isird.org/ International Society of Invertebrate Reproduction and Development]
** International Congress for Invertebrate Reproduction and Development (ICIRD) — proceedings
** [https://www.tandfonline.com/journals/tinv20 Invertebrate Reproduction & Development] (journal) {{ISSN|2157-0272}} {{OCLC|633196745}}
{{refend}}

== External links ==

* {{cite book |author1=A. R. Maggenti |author2=S. Gardner |url=http://digitalcommons.unl.edu/onlinedictinvertzoology/ |title=Online Dictionary of Invertebrate Zoology |year=2005 |access-date=7 September 2005 |archive-date=26 December 2018 |archive-url=https://web.archive.org/web/20181226124609/http://digitalcommons.unl.edu/onlinedictinvertzoology/%20 |url-status=live }}
* [https://web.archive.org/web/20160305154711/https://www.buglife.org.uk/News/Endangeredspeciessculpture.htm  Buglife (UK)]
* [https://web.archive.org/web/20080820143549/http://www.africaninvertebrates.org.za/ ''African Invertebrates'']

{{Authority control}}
{{Use dmy dates|date=April 2017}}

[[Category:Invertebrates| 01]]
[[Category:Zoology]]
[[Category:Paraphyletic groups]]
[[Category:Obsolete animal taxa]]