Editing Onychophora (section)

===Slime papillae===
[[File:Ooperipatellus viridimaculatus 34495501.jpg|thumb|Head region of ''[[Ooperipatellus viridimaculatus]]'', showing its oral papillae and mouthparts|left|220x220px]]
On the third head segment, to the left and right of the mouth, are two openings called "oral papillae", with each containing a large, heavily branched slime gland.<ref name=":2">{{cite journal |last1=Morera-Brenes |first1=B. |last2=Monge-Najera |first2=J. |date=2010 |title=A new giant species of placented worm and the mechanism by which onychophorans weave their nets (onychophora: Peripatidae) |url=http://www.kerwa.ucr.ac.cr/handle/10669/4483 |url-status=dead |journal=Revista de Biología Tropical |volume=58 |issue=4 |pages=1127–1142 |arxiv=1511.00983 |doi=10.15517/rbt.v58i4.5398 |pmid=21246983 |archive-url=https://web.archive.org/web/20150402132847/http://www.kerwa.ucr.ac.cr/handle/10669/4483 |archive-date=2015-04-02}}</ref> These slime glands lie roughly in the center of a velvet worm's body and secrete a sort of milky-white slime. The slime is used to both ensnare [[prey]] and act as a distraction for defensive purposes.<ref name=":2" /> In certain species, an organ connected to the slime gland known as the "slime conductor" is broadened into a reservoir, allowing it to hold pre-produced slime.<ref name=":3">{{cite journal |last1=Concha |first1=Andrés |last2=Mellado |first2=Paula |last3=Morera-Brenes |first3=B. |last4=Sampaio Costa |first4=Cristiano |last5=Mahadevan |first5=L. |last6=Monge-Nájera |first6=Julián |date=17 March 2015 |title=Oscillation of the velvet worm slime jet by passive hydrodynamic instability |journal=Nature Communications |volume=6 |page=6292 |bibcode=2015NatCo...6.6292C |doi=10.1038/ncomms7292 |pmc=4382676 |pmid=25780995}}</ref>

Velvet worm slime glands and oral papilla are likely modified and repurposed limbs. The glands themselves are probably modified crural glands.<ref name=":3" /> All three structures correspond to an [[evolution]]ary origin in the leg pairs of the other segments.{{citation needed|date=February 2016}}

==== Slime ====
[[File:Peripatopsis overbergiensis 45218773.gif|thumb|''[[Peripatopsis overbergiensis]]'' squirting its slime]]The Onychophora forcefully [[projectile use by living systems|squirt]] glue-like slime{{efn|The secretion ejected by onychophorans is sometimes referred to as ''glue'', but termed ''slime'' in current scientific literature; e.g. {{harvp|Benkendorff|Beardmore|Gooley|Packer|Tait |1999}},<ref name=Benkendorff1999/> {{harvp|Baer|Mayer|2012}},<ref name=Baer2012/> {{harvp|Concha|Mellado|Morera-Brenes|Sampaio-Costa|Mahadevan|Monge-Nájera|2014|ref=none}},<ref name=:3/> and others.<ref>{{cite journal |last1 = Baer |first1 = A. |last2 = de&nbsp;Sena Oliveira | first2 = I. |last3 = Steinhagen |first3 = M. |last4 = Beck-Sickinger |first4 = A.G. |last5 = Mayer |first5 = G. |year = 2014 |title = Slime protein profiling: A non-invasive tool for species identification in Onychophora (velvet worms) |journal = Journal of Zoological Systematics and Evolutionary Research| volume = 52 |issue = 4 |pages = 265–272 | doi = 10.1111/jzs.12070 |doi-access = free }}</ref>
}} from their oral papillae; they do so either in defense against predators or to capture prey.<ref name="Baer2012">{{cite journal |last1=Baer |first1=Alexander |last2=Mayer |first2=Georg |date=October 2012 |title=Comparative anatomy of slime glands in onychophora (velvet worms) |journal=Journal of Morphology |volume=273 |issue=10 |pages=1079–1088 |doi=10.1002/jmor.20044 |pmid=22707384 |s2cid=701697}}</ref> The openings of the glands that produce the slime are in the papillae, a pair of highly modified limbs on the sides of the head below the antennae. Inside, they have a syringe-like system that, by a geometric amplifier, allows for fast squirt using slow muscular contraction.<ref name=":3"/> High speed films show the animal expelling two streams of adhesive liquid through a small opening (50–200 [[micron]]s) at a speed of {{convert|3|to|5|m/s|ft/s|abbr=on|sigfig=1}}.<ref name=":3" /> The interplay between the elasticity of oral papillae and the fast unsteady flow produces a passive oscillatory motion (30–60&nbsp;Hz) of the oral papillae.<ref name=":3" /> The oscillation causes the streams to cross in mid air, weaving a disordered net; the velvet worms can control only the general direction where the net is thrown.<ref name="Morera-Brenes2010">{{cite journal |last1=Morera-Brenes |first1=Bernal |last2=Monge-Nájera |first2=Julián |date=December 2010 |title=A new giant species of placented worm and the mechanism by which onychophorans weave their nets (onychophora: Peripatidae) |journal=Revista Biologìa Tropical |volume=58 |pages=1127–1142 |arxiv=1511.00983}}</ref>

The slime glands themselves are deep inside the body cavity, each at the end of a tube more than half the length of the body. The tube both conducts the fluid and stores it until it is required. The distance that the animal can propel the slime varies; usually it squirts it about a centimetre,<ref name="Benkendorff1999">{{cite journal |last1=Benkendorff |first1=Kirsten |last2=Beardmore |first2=Kate |last3=Gooley |first3=Andrew A. |last4=Packer |first4=Nicolle H. |last5=Tait |first5=Noel N. |date=December 1999 |title=Characterisation of the slime gland secretion from the peripatus, ''Euperipatoides kanangrensis'' (Onychophora: Peripatopsidae) |journal=Comparative Biochemistry and Physiology B |volume=124 |issue=4 |pages=457–65 |doi=10.1016/S0305-0491(99)00145-5}}</ref> but the maximal range has variously been reported to be ten centimetres,<ref name="ISBN 978-0-7993-4689-3">{{cite book |last1=Holm |first1=Erik |url=http://www.LAPA.co.za |title=Goggo Guide |last2=Dippenaar-Schoeman |publisher=LAPA publishers |year=2010 |isbn=978-0-7993-4689-3 |first12=Ansie}}{{page needed|date=November 2014}}</ref> or even nearly a foot,<ref name="CNH4">{{cite book |last1=Harmer |first1=Sidney Frederic |title=Peripatus, Myriapods, Insects |last2=Shipley |first2=Arthur Everett |publisher=Macmillan Company |year=1922 |series=The Cambridge Natural History |volume=5 |display-authors=etal}}{{page needed|date=November 2014}}</ref> although accuracy drops with range.<ref name="Read1987" /> It is not clear to what extent the range varies with the species and other factors. One squirt usually suffices to snare a prey item, although larger prey may be further immobilised by smaller squirts targeted at the limbs; additionally, the fangs of spiders are sometimes targeted.<ref name="Read1987" /> Upon ejection, it forms a net of threads about twenty microns in diameter, with evenly spaced droplets of viscous adhesive fluid along their length.<ref name="Benkendorff1999" /> It subsequently dries, shrinking, losing its stickiness, and becoming brittle.<ref name="Benkendorff1999" /> Onychophora eat their dried slime when they can, which seems provident, since an onychophoran requires about 24&nbsp;days to replenish an exhausted slime repository.<ref name="Read1987" />

The slime can account for up to 11% of the organism's dry weight<ref name="Read1987" /> and is 90% water; its dry residue consists mainly of proteins—primarily a [[collagen]]-type protein.<ref name="Benkendorff1999" /> 1.3% of the slime's dry weight consists of sugars, mainly [[galactosamine]].<ref name="Benkendorff1999" /> The slime also contains lipids and the [[surfactant]] [[nonylphenol]]. Onychophora are the only organisms known to produce this latter substance.<ref name="Benkendorff1999" /> It tastes "slightly bitter and at the same time somewhat astringent".<ref>{{cite journal |last=Moseley |first=H.N. |year=1874 |title=On the structure and development of ''Peripatus capensis'' |url=https://zenodo.org/record/1432452 |journal=Philosophical Transactions of the Royal Society of London |volume=164 |pages=757–82 |bibcode=1874RSPT..164..757M |doi=10.1098/rstl.1874.0022 |jstor=109116 |doi-access=free}}</ref> The proteinaceous composition accounts for the slime's high [[tensile strength]] and stretchiness.<ref name="Benkendorff1999" /> The lipid and nonylphenol constituents may serve one of two purposes: They may line the ejection channel, stopping the slime from sticking to the organism when it is secreted; or they may slow the drying process long enough for the slime to reach its target.<ref name="Benkendorff1999" />