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  Jet propulsion
  The topic of locomotion is divided into sections of jet propulsion, considered here, and CRAWLING and NAVIGATION & LEARNING considered elsewhere.

drawing of an octopus to show mantle-cavity parts relating to jet propulsion drawing of an octopus to show mantle-cavity parts relating to jet propulsion
The process of jet propulsion in an octopus is presented in simplified form in these 2 drawings. The process is the same whether the animal is simply ventilating or whether it is jetting. The mantle opening is divided into 2 openings separated by the siphon. The openings are closed by flapper valves that pop into place during exhalation, thus forcing all the water out the siphon. Correct alignment of the 2 mantle-cavity openings in photograph of an octopus showing orientation of flapper valve on right side of mantle cavityrelation to the siphon is ensured by symmetrically placed cartilaginous photograph of cartilaginous locking devices on either sid of the mantle cavity of a giant squid Mortoteuthis robustalocking devices. Correct alignment ensures that the 2 flapper valves open and close without back-flow leakage during exhalation. Prior to its entry into the siphon the flow picks up discharge from the anus, nephridiopores, and ink from the ink sac.

Zip-loc configuration of one side
of the mantle opening in a giant squid Moroteuthis robusta. The left side
of the mantle is at the top of the
photo, while the soft edge of the
flapper valve is at the bottom

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photograph of an octopus Enteroctopus dolfleini commencing a ventilatory cycle taken from a video

CLICK HERE to see a video of an octopus Enteroctopus dolfleini ventilating its mantle cavity. The siphon, which in this view is pointing to the octopus' right, can be moved in any direction.

NOTE the video replays automatically

Research study 1

drawing of mantle of squid showing relationship of circular and radial musculaturephotograph of squid Loligo opalescens with egg sausage courtesy NOAA, Federal Government, WashingtonWater flow through a squid functions both for gas exchange and jetting locomotion.  Studies on the pelagic squid Doryteuthis opalescens at the University of British Columbia indicate a different pattern for each function.  During escape jetting, for example, there are 3 phases: 1) filling of the mantle cavity powered largely by elastic recoil of the mantle wall from the previous jetting with a small contribution from the radial muscles, 2) hyperinflation of the mantle cavity through contraction of radial muscles drawing more water in, and 3) expulsion of the water powered by contraction of circular muscles. Hyperinflation serves to fill the mantle cavity maximally, making the jet more powerful.  In comparison, the more gentle pulsation of gas exchange is done in 2 ways, either by radial-muscle power or circular-muscle power, but both being antagonised by mantle tissue elasticity. The study emphasises the important role played by storage of elastic energy in the connective tissue-fibers of the mantle wall in both locomotion and gas exchange.  Gosline et al. 1983 J Exp Biol 104: 97; for an account of temperature-compensation effects and prey-capture experience on escape jetting in squids Doryteuthis opalescens see Neumeister et al. 2000 J Exp Biol 203: 547 and Preuss & Gilly 2000 J Exp Biol 203: 559. Photograph of squid courtesy NOAA, Federal Government, Washington.

photograph of the siphon of a Humboldt squid Dosidicus gigas taken from a video

CLICK HERE to see a video of a moribund Humboldt squid Dosidicus gigas jetting once gently and then culminating in a larger expulsion that douses the video camera.

NOTE the video replays automatically

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Research study 2

graph showing cost of transport in different invertebrates and fishes, including cephalopodsa, relative to live mass Squids locomote by a combination of finning and jetting, and open-water species can maintain a pace of 1-2km . h-1 for weeks at a time.  During fast jetting the fins are rolled up to reduce drag.  How does the jet-propulsion swimming of a squid compare with tail-wagging swimming of a fish?  table showing comparative costs of swimming in salmon vs. squidsNot well, in fact.  A squid uses 3 times as much energy to travel half as fast as a sockeye salmon of comparable size (see table on Right):

The graph shows the net cost of transport for various tail-wagging fishes, including sockeye salmon, in comparison with several species of planktonic crustaceans and 3 species of squids.  The authors note the one advantage of squids over fishes in this regard is that the jet system automatically increases water flow over the ctenidia as swimming speed increases.  Fishes expend increasing amounts of energy to ventilate their gills with increased velocity. O’Dor & Webber 1986 Can J Zool 64; 1591; O’Dor 1982 Can J Fish Aquat Sci 39: 580.

Research study 3

photograph of octopus Enteroctopus dolfleini jetting backwardsJetting is used by octopuses not just for locomotion, but also for cleaning out potential homes, digging clams from sand, and chasing fishes away from prey remains.  Mather & Anderson 1999 J Comp Psychol 113: 333.



Enteroctopus dolfleini in full jetting flight backwards (Leftwards
in the photo). The siphon is partly collapsed at the end of a jet cycle,
and the mantle openings are soon to open with a new intake of water.
Note that the octopus is looking backwards to see where it is going

photograph of an octopus being held by a SCUBA-diver

CLICK HERE to see a video of a small octopus, either Octopus rubescens or Enteroctopus dolfleini, trying to get away from being held by a SCUBA-diver.

NOTE the video replays automatically

Research study 4

Research at the Monterey Bay Aquarium Research Institute at Moss Landing, California and in situ video recordings in Monterey Bay with the ROV Ventana show that squids Doryteuthis opalescens of 10-120mm mantle length swim at an average velocity of 0.2m . sec-1 with burst speeds up to 1.6m . sec-1.  The authors provide a variety of morphometric measurements that allow handy identification of size of squids from the ROV video recordings.  For example, a linear regression can predict dorsal mantle length (ML) from a dimensionless ratio of ML over eye diameter taken from video records.  Zeidberg 2004 J Exp Biol 207: 4195.

CLICK HERE to see a selection of video clips of various swimming squids, octopuses, and cuttlefishes provided by the Monterey Bay Aquarium, California