Editing Jet propulsion (section)

==Jet-propelled animals==
{{Main|Aquatic locomotion#Jet propulsion}}

[[Cephalopod]]s such as squid use jet propulsion for rapid [[Anti-predator adaptation#Escape|escape from predators]]; they use other mechanisms for slow swimming. The jet is produced by ejecting water through a [[Siphon (mollusc)|siphon]], which typically narrows to a small opening to produce the maximum exhalent velocity. The water passes through the gills prior to exhalation, fulfilling the dual purpose of respiration and locomotion.<ref name='Packard1972'/> 
[[File:Swimming behaviour of Notarchus punctatus.png|thumb|175px|Illustration of [[Notarchus|Notarchus punctatus]] swimming motion <ref name=":0">{{Cite book |last=Martin |first=Rainer |title=On the swimming behaviour and biology of ''Notarchus punctatus'' Phillipi (Gastropoda, Opisthobranchia) |year=1966 |series=Pubblicazioni della Stazione Zoologica di Napoli |volume=35 |pages=61–75}}</ref>]]
Sea hares ([[Gastropoda]], [[Opisthobranchia]]) employ a similar method, but without the sophisticated neurological machinery of cephalopods and the absence of fins to steer their movements, they navigate somewhat more clumsily.<ref name=":0" />

The swimming cycle has two phases: (A) the propulsive phase, where the animal ejects a jet of water to move, and (B) the rolling phase, where it performs a somersault to reset its position.<ref name=":0" />

A study by Mazzarelli (1893) suggests that [[Dromia]] crabs may be predators of [[Notarchus]]. In a confined tank with little sea water, two sea hares suffocated after being tightly held by the crab for hours, despite showing no visible injuries upon dissection. It is unclear if this behavior occurs in the wild, but Notarchus may escape simply by swimming if space allows.<ref name=":0" /><ref>{{Cite journal |last=Mazzarelli |first=G. |date=1893 |title=Monografia delle Aplysiidae del Golfo di Napoli |url=https://gdz.sub.uni-goettingen.de/id/PPN641030126 |journal=Memorie della Società Italiana delle Scienze |volume=9 |pages=1–222}}</ref>

Some [[teleost fish]] have also developed jet propulsion, passing water through the gills to supplement fin-driven motion.<ref name="Hanken1993">{{cite book |last=Wake |first=M.H. |title=Craniology: Getting a Head: The Skull |publisher=[[University of Chicago Press]] |year=1993 |isbn=978-0-226-31573-7 |editor-last=Hanken |editor-first=James |volume=3 |at=p. 201 |chapter=The Skull as a Locomotor Organ |doi=10.1126/science.263.5154.1779 |editor-last2=Hall |editor-first2=Brian K.}}</ref><ref>{{Cite book |last=Lindsey |first=C. C. |title=Form, Function, and Locomotory Habits in Fish |publisher=Academic Press |year=1978 |isbn=978-0-12-350407-4 |editor-last=Hoar |series=Fish Physiology |volume=7 |pages=1–100 |doi=10.1016/S1546-5098(08)60163-6 |issn=1546-5098 |editor-last2=Randall}}</ref>

In some [[dragonfly]] larvae, jet propulsion is achieved by the expulsion of water from a specialised cavity through the anus. Given the small size of the organism, a great speed is achieved.<ref name='Mill2004'>{{Cite journal| first1 = P. J.| first2 = R. S. | title = Jet-propulsion in anisopteran dragonfly larvae| last1 = Mill | journal = Journal of Comparative Physiology| volume = 97| issue = 4 | pages = 329–338 | year = 1975 | doi = 10.1007/BF00631969| last2 =  Pickard | s2cid = 45066664 }}</ref>

Scallops and [[cardiids]],<ref>{{Nautilus|chapter=32. Locomotion of ''Nautilus''|author=Chamberlain Jr, John A.}}</ref> [[siphonophore]]s,<ref name="ref_" >{{Cite journal | last1 = Bone | first1 = Q. | last2 = Trueman | first2 = E. R. | doi = 10.1017/S0025315400057271 | title = Jet propulsion of the calycophoran siphonophores ''Chelophyes'' and ''Abylopsis'' | journal = Journal of the Marine Biological Association of the United Kingdom | volume = 62 | issue = 2 | pages = 263–276 | year = 2009 | s2cid = 84754313 }}</ref> tunicates (such as [[salps]]),<ref name="ref_a" >{{Cite journal | last1 = Bone | first1 = Q. | last2 = Trueman | first2 = E. R. | doi = 10.1111/j.1469-7998.1983.tb05071.x | title = Jet propulsion in salps (Tunicata: Thaliacea) | journal = Journal of Zoology | volume = 201 | issue = 4 | pages = 481–506 | year = 2009 }}</ref><ref name="ref_b" >{{Cite journal | last1 = Bone | first1 = Q. | last2 = Trueman | first2 = E. | doi = 10.1016/0022-0981(84)90059-5 | title = Jet propulsion in Doliolum (Tunicata: Thaliacea) | journal = Journal of Experimental Marine Biology and Ecology | volume = 76 | issue = 2 | pages = 105–118 | year = 1984 }}</ref> and [[Polyorchis|some jellyfish]]<ref>{{cite journal |last1=Demont |first1=M. Edwin |last2=Gosline |first2=John M. |date=January 1, 1988 |title=Mechanics of Jet Propulsion in the Hydromedusan Jellyfish, ''Polyorchis Pexicillatus'': I. Mechanical Properties of the Locomotor Structure |url=http://jeb.biologists.org/cgi/content/abstract/134/1/313 |journal=J. Exp. Biol. |volume=134 |issue=134 |pages=313–332 |bibcode=1988JExpB.134..313D |doi=10.1242/jeb.134.1.313}}</ref><ref>{{cite journal |last1=Demont |first1=M. Edwin |last2=Gosline |first2=John M. |date=January 1, 1988 |title=Mechanics of Jet Propulsion in the Hydromedusan Jellyfish, ''Polyorchis Pexicillatus'': II. Energetics of the Jet Cycle |url=http://jeb.biologists.org/cgi/content/abstract/134/1/333 |journal=J. Exp. Biol. |volume=134 |issue=134 |pages=333–345 |bibcode=1988JExpB.134..333D |doi=10.1242/jeb.134.1.333}}</ref><ref>{{cite journal |last1=Demont |first1=M. Edwin |last2=Gosline |first2=John M. |date=January 1, 1988 |title=Mechanics of Jet Propulsion in the Hydromedusan Jellyfish, ''Polyorchis Pexicillatus'': III. A Natural Resonating Bell; The Presence and Importance of a Resonant Phenomenon in the Locomotor Structure |url=http://jeb.biologists.org/cgi/content/abstract/134/1/347 |journal=J. Exp. Biol. |volume=134 |issue=134 |pages=347–361 |doi=10.1242/jeb.134.1.347}}</ref> also employ jet propulsion.  The most efficient jet-propelled organisms are the salps,<ref name="ref_a" /> which use an order of magnitude less energy (per kilogram per metre) than squid.<ref name="ref_c">{{Cite journal | last1 = Madin | first1 = L. P. | title = Aspects of jet propulsion in salps | journal = Canadian Journal of Zoology | volume = 68 | issue = 4 | pages = 765–777 | year = 1990 | doi = 10.1139/z90-111 }}</ref>