Editing Squid (section)

==Behaviour==

===Locomotion===
[[File:Euprymna scolopes - image.pbio.v12.i02.g001.png|thumb|left|upright=1.2|Hawaiian bobtail squid swimming slowly by undulating its fins]]

Squid can move about in several different ways. Slow movement is achieved by a gentle undulation of the muscular lateral fins on either side of the trunk which drives the animal forward. A more common means of locomotion providing sustained movement is achieved using jetting, during which contraction of the muscular wall of the mantle cavity provides jet propulsion.<ref name=Ruppert/>

Slow jetting is used for ordinary locomotion, and ventilation of the gills is achieved at the same time. The circular muscles in the mantle wall contract; this causes the inhalant valve to close, the exhalant valve to open and the mantle edge to lock tightly around the head. Water is forced out through the funnel which is pointed in the opposite direction to the required direction of travel. The inhalant phase is initiated by the relaxation of the circular muscles causes them to stretch, the connective tissue in the mantle wall recoils elastically, the mantle cavity expands causing the inhalant valve to open, the exhalant valve to close and water to flow into the cavity. This cycle of exhalation and inhalation is repeated to provide continuous locomotion.<ref name=Ruppert/>

Fast jetting is an escape response. In this form of locomotion, radial muscles in the mantle wall are involved as well as circular ones, making it possible to hyper-inflate the mantle cavity with a larger volume of water than during slow jetting. On contraction, water flows out with great force, the funnel always being pointed anteriorly, and travel is backwards. During this means of locomotion, some squid exit the water in a similar way to [[flying fish]], gliding through the air for up to {{convert|50|m|ft|-1|abbr=on}}, and occasionally ending up on the decks of ships.<ref name=Ruppert/>

===Feeding===
Squid are [[carnivore]]s, and, with their strong arms and suckers, can overwhelm relatively large animals efficiently. Prey is identified by sight or by touch, grabbed by the tentacles which can be shot out with great rapidity, brought back to within reach of the arms, and held by the hooks and suckers on their surface.<ref name=Messenger/> In some species, the squid's saliva contains [[toxin]]s which act to subdue the prey. These are injected into its bloodstream when the prey is bitten, along with vasodilators and chemicals to stimulate the heart, and quickly circulate to all parts of its body.<ref name=Ruppert/> The deep sea squid ''[[Taningia danae]]'' has been filmed releasing blinding flashes of light from large photophores on its arms to illuminate and disorientate potential prey.<ref>{{cite journal |author1=Kubodera, T. |author2=Koyama, Y. |author3=Mori, K. |year=2006 |title=Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, ''Taningia danae'' |journal=Proceedings of the Royal Society B: Biological Sciences |volume=274 |issue=1613 |pages=1029–1034 |doi=10.1098/rspb.2006.0236 |pmid=17301020 |pmc=2124471 |url=http://www.pubs.royalsoc.ac.uk/media/proceedings_b/papers/RSPB20060236.pdf |access-date=13 January 2019 |archive-url=https://web.archive.org/web/20070216024900/http://www.pubs.royalsoc.ac.uk/media/proceedings_b/papers/RSPB20060236.pdf |archive-date=16 February 2007 |df=dmy-all }}</ref>

[[File:Ventouse calmar.jpg|thumb|The whip-like tentacles of ''[[Mastigoteuthis]]'' are covered with tiny suckers to catch small organisms like [[flypaper]].]]

Although squid can catch large prey, the mouth is relatively small, and the food must be cut into pieces by the chitinous beak with its powerful muscles before being swallowed. The radula is located in the buccal cavity and has multiple rows of tiny teeth that draw the food backwards and grind it in pieces.<ref name=Ruppert/> The deep sea squid ''[[Mastigoteuthis]]'' has the whole length of its whip-like tentacles covered with tiny suckers; it probably catches small organisms in the same way that [[flypaper]] traps flies. The tentacles of some [[bathypelagic]] squids bear [[photophore]]s which may bring food within its reach by attracting prey.<ref name=Messenger>{{cite book |author1=Hanlon, Roger T. |author2=Messenger, John B. |title=Cephalopod Behaviour |url=https://books.google.com/books?id=Nxfv6xZZ6WYC&pg=PA47 |year=1998 |publisher=Cambridge University Press |isbn=978-0-521-64583-6 |pages=47–49}}</ref>

Squid are among the most intelligent invertebrates. For example, groups of [[Humboldt squid]] hunt cooperatively, spiralling up through the water at night and coordinating their vertical and horizontal movements while foraging.<ref>{{cite web|url=http://deepseanews.com/2012/06/coordinated-hunting-in-red-devils/ |title=Coordinated Hunting in Red Devils |publisher=Deep Sea News|author=Smith, Helena|date= 5 June 2012 |url-status=live |archive-url=https://web.archive.org/web/20120611054534/http://deepseanews.com/2012/06/coordinated-hunting-in-red-devils/|archive-date=11 June 2012|access-date=9 December 2018}}</ref>

===Reproduction===
[[File:Squid colors 2.jpg|thumb|left|The [[Caribbean reef squid]] (''Sepioteuthis sepioidea'') employs a complex array of colour changes during courtship and social interactions.]]

Courtship in squid takes place in the open water and involves the male selecting a female, the female responding, and the transfer by the male of spermatophores to the female. In many instances, the male may display to identify himself to the female and drive off any potential competitors.<ref>{{cite journal |author=Arnold, John M. |year=1965 |title=Observations on the Mating Behavior of the Squid ''Sepioteuthis sepioidea'' |journal=Bulletin of Marine Science |volume=15 |issue=1 |pages=216–222 |url=https://www.ingentaconnect.com/content/umrsmas/bullmar/1965/00000015/00000001/art00008 }}</ref> Elaborate changes in body patterning take place in some species in both agonistic and courtship behaviour. The [[Caribbean reef squid]] (''Sepioteuthis sepioidea''), for example, employs a complex array of colour changes during courtship and social interactions and has a range of about 16 body patterns in its repertoire.<ref>{{cite book |author1=Hanlon, Roger T. |author2=Messenger, John B. |title=Cephalopod Behaviour|url=https://books.google.com/books?id=Nxfv6xZZ6WYC&pg=PA42 |year=1998 |publisher=[[Cambridge University Press]] |isbn=978-0-521-64583-6 |page=42}}</ref>

The pair adopt a head-to-head position, and "jaw locking" may take place, in a similar manner to that adopted by some [[cichlid]] fish.<ref>{{cite journal |author1=Jackson, George D. |author2=Jackson, Christine H. |year=2004 |title=Mating and spermatophore placement in the onychoteuthid squid ''Moroteuthis ingens'' |journal=Journal of the Marine Biological Association of the United Kingdom |volume=84 |issue=4 |pages=783–784 |doi=10.1017/S0025315404009932 |bibcode=2004JMBUK..84..783J |s2cid=86725399 }}</ref> The heterodactylus of the male is used to transfer the spermatophore and deposit it in the female's mantle cavity in the position appropriate for the species; this may be adjacent to the gonopore or in a seminal receptacle.<ref name=Ruppert/>

[[File:Squid Eggs (6997601241).jpg|thumb|Squid eggs<!--in the Philippines-->]]

The sperm may be used immediately or may be stored. As the eggs pass down the oviduct, they are wrapped in a gelatinous coating, before continuing to the mantle cavity, where they are fertilised. In ''[[Loligo]]'', further coatings are added by the nidimental glands in the walls of the cavity and the eggs leave through a funnel formed by the arms. The female attaches them to the substrate in strings or groups, the coating layers swelling and hardening after contact with sea water. ''Loligo'' sometimes forms breeding aggregations which may create a "community pile" of egg strings. Some pelagic and deep sea squid do not attach their egg masses, which float freely.<ref name=Ruppert/>