Was that it's butthole? That big hole? What is that? I may or may not have gotten turned on watching that.
From Wikipedia:
Locomotion and buoyancyEdit
Octopuses swim headfirst, with arms trailing behind
While most cephalopods can move by
jet propulsion, this is a very energy-consuming way to travel compared to the tail propulsion used by fish.
[36] The efficiency of a
propellor-driven
waterjet(i.e.
Froude efficiency) is a more efficient model than
rocketefficiency.
[37] The relative efficiency of
jet propulsion decreases further as animal size increases;
paralarvae are far more efficient than juvenile and adult individuals.
[38] Since the
Paleozoic era, as competition with
fish produced an environment where efficient motion was crucial to survival, jet propulsion has taken a back role, with
fins and
tentacles used to maintain a steady velocity.
[3] Whilst jet propulsion is never the sole mode of locomotion,
[3]:208 the stop-start motion provided by the jets continues to be useful for providing bursts of high speed - not least when capturing
prey or avoiding
predators.
[3]Indeed, it makes cephalopods the fastest marine invertebrates,
[5]refaceand they can out-accelerate most fish.
[31] The jet is supplemented with fin motion; in the squid, the fins flap each time that a jet is released, amplifying the thrust; they are then extended between jets (presumably to avoid sinking).
[38] Oxygenated water is taken into the
mantle cavity to the
gills and through muscular contraction of this cavity, the spent water is expelled through the
hyponome, created by a fold in the mantle. The size difference between the posterior and anterior ends of this organ control the speed of the jet the organism can produce.
[39] The velocity of the organism can be accurately predicted for a given mass and morphology of animal.
[40] Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by pointing it in different directions.
[41] Some cephalopods accompany this expulsion of water with a gunshot-like popping noise, thought to function to frighten away potential predators.
[42]
Link to full article:
Cephalopod - Wikipedia, the free encyclopedia
FRAT: That's it's jet hole.