Lecture 8, Bio 325 Jetting locomotion by prolate and oblate medusae Squid locomotion Assigned...
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Lecture 8, Bio 325 Jetting locomotion by prolate and oblate medusae Squid locomotion Assigned reading: Dabiri J. O., Colin S.P., Costello J.H., Gharib, M. 2005. Flow patterns generated by oblate medusan jellyfish: field measurements and laboratory analyses. Journal of experimental Biology 208: 1257- in which they discover the stopping vortex ring which contributes to medusa swimming. JELLYFISH FORM AND FUNCTION Website by John H. Costello & Sean P. Colin, Roger Williams University. See this website for information about jellyfish swimming: fox.rwu.edu/jellies/index.html Gemmell B.J. et al. 2013. Passive energy recapture in jellyfish contributes to propulsive advantage over other metazoans. PNAS 110: 17904- Gosline J.M., & Demont M.E. 1984. Jet-propelled swimming in squids. Scientific American 252: 96-103.
Lecture 8, Bio 325 Jetting locomotion by prolate and oblate medusae Squid locomotion Assigned reading: Dabiri J. O., Colin S.P., Costello J.H., Gharib,
Lecture 8, Bio 325 Jetting locomotion by prolate and oblate
medusae Squid locomotion Assigned reading: Dabiri J. O., Colin
S.P., Costello J.H., Gharib, M. 2005. Flow patterns generated by
oblate medusan jellyfish: field measurements and laboratory
analyses. Journal of experimental Biology 208: 1257- in which they
discover the stopping vortex ring which contributes to medusa
swimming. JELLYFISH FORM AND FUNCTION Website by John H. Costello
& Sean P. Colin, Roger Williams University. See this website
for information about jellyfish swimming:
fox.rwu.edu/jellies/index.html Gemmell B.J. et al. 2013. Passive
energy recapture in jellyfish contributes to propulsive advantage
over other metazoans. PNAS 110: 17904- Gosline J.M., & Demont
M.E. 1984. Jet-propelled swimming in squids. Scientific American
252: 96-103.
Slide 2
Vortices When I draw a canoe paddle through still water on a
lake, I see small vortices trail off the paddle edges downflow.
When I stir coffee or let water down the drain I make vortices.
Smokers blow smoke rings and cetaceans blow bubble rings. This
picture is of a vortex forming on the upstream side of a tidal
turbine*. These rings travel through the fluid. Fluids like water
and air exhibit flow and a vortex is simply flow that spins.
Toroid: doughnut-shaped object, e.g., O ring toroidal vortices
produced behind swimming jellyfish *the hole in the centre is ~15
cm in diameter songofthepaddle
Slide 3
Cnidarian morphs: Polyps (e.g., sea anemones) and Medusae
(e.g., Jellyfish) -In contrast to the polypoid mesoglea (middle
layer), which is more or less thin, the medusoid mesoglea is
extremely thick and constitutes the bulk of the animal. (from
Barnes) What is the function of mesoglea in a jellyfish? Buoyancy?
Antagonist? Why is the mesoglea of the locomotory morph so much
more important (based on its abundance) than the mesoglea of the
sessile morph? Mesoglea another body material: a pliant composite
material The mesoglea of jellyfish is adapted as a viscoelastic
antagonist of the bells circular muscles.
Slide 4
Medusae can be bullet-shaped (prolate) or flatter (oblate)
Velum has to do with shaping vortices Oblate medusae have smaller
velums than prolate, contract more slowly when swimming and throw
larger amounts of water behind them as they jet. prolate
oblate
Slide 5
Jet propulsion and vortices Animal Literature More complex:
Dabiri et al. : jellyfish jetts out seawater making 2 vortex rings
--doughnuts of water that are continuously rolling into themselves.
oblate medusaBarnes: Simplest swimming explanation: seawater
beneath the umbrella is incompressible; coronal muscle, powerful
circular fibres on the subumbrella contracts to jet out the
subumbrellar fluid.
Slide 6
Jetting by Jellyfish
Slide 7
Schematic of a jetting medusa with vortex rings in the wake.
Dabiri J O et al. J Exp Biol 2005;208:1257-1265 2005 by The Company
of Biologists Ltd Jetting medusa with vortex rings in wake Periodic
bell contractions decrease volume of subumbrellar cavity,
displacing out the high bulk modulus (incompressible) water as a
jet: jet propulsion. Swimming cycle: fluid efflux emerges during
bell contraction: a toroidal volume of rotating fluid known as the
power stroke starting vortex ring. This travels downstream is shed
-- behind the forward progress of the medusa. There are two things
in the wake: this vortex and a central jet (D). The cycle continues
with a second fluid efflux shed during bell relaxation and
recovery, a recovery stroke stopping vortex ring as mesoglea
returns its elastic force. of distortion, elastic force)
Slide 8
Kinematics of the starting, stopping and co-joined lateral
vortex structures. Dabiri J O et al. J Exp Biol 2005;208:1257-1265
2005 by The Company of Biologists Ltd Dye used to visualize the
behaviour of the fluid in the wake of the swimming medusa. Starting
vortex ring involves fluid originating from regions inside the
subumbrellar volume, but also from outside the bell via entrainment
of ambient fluid [flow induced by vortex rotation]; motion of this
ring is oriented at an angle away from the bell margin toward the
central axis of the bell and downstream (broken arrows). ambient:
surrounding solid arrows: direction of vortex rotation
Slide 9
Kinematics of the starting, stopping and co-joined lateral
vortex structures. Stopping vortex ring: bell coronal muscle fibres
relax and bell opens (mesoglea returns energy for this that
originated with the coronal muscle). This bell recoil makes a
stopping vortex initially within the subumbrellar cavity. But fluid
originating from outside the bell is also entrained: it is drawn
toward the subumbrellar cavity.
Slide 10
My first attempt to make these kinematics comprehensible to
make the information my own. Drawings, scribbles are important to
me in this process. I recommend something like this for both
learning and for testing. L1/L2, adjacent lateral vortex
superstructures created between the two toroids. Stopping vortex
lateral structure contributes to advance of swimmer during recovery
cycle.
Slide 11
Gemmell B.J. et al. 2013. Passive energy recapture in jellyfish
contributes to propulsive advantage over other metazoans. PNAS 110:
17904- Gelatinous zooplankton (jellyfish) blooms are problems in
perturbed ecosystems. How are jellyfish able to do so much better
than the fish? Jellyfish are such apparently poor swimmers, so
primitive and inefficient in comparison to fish; how can they so
thoroughly outcompete fish in these degraded habitats? Note that
both medusae and fish have to pursue their food in the water
column, i.e., swim after what they eat rather than filter it out of
currents bringing food to them: we are comparing animal predators
that pursue their food and must rely on direct contact with prey to
feed. The passive energy recapture involved in the vortices is
credited with this greater locomotion efficiency: [from abstract of
Gemmell] ...jellyfish exhibit a unique mechanism of passive energy
recapture, which is exploited to allow them to travel 30% further
each swimming cycle, thereby reducing metabolic energy demand by
swimming muscles. Jellyfish are one of the most energetically
efficient propulsors on the planet.
Slide 12
Nature News, October 2013, Ed Yong: The sockeye salmon is a
sleek torpedo that uses its strong muscles to leap up waterfalls.
The moon jellyfish (Aurelia aurita) is a flimsy blob that drifts
along like a gently pulsating bell. The salmon is obviously the
more powerful swimmer, but a study has revealed that the jellyfish
outclasses it in efficiency. For its mass the jellyfish spends less
energy to travel a given distance than any other swimming animal.
When moon jellyfish contract their umbrella-shaped bells, they
create two vortex rings doughnuts of water that are continuously
rolling into themselves. The creature sheds the first ring in its
wake, propelling itself forward. As the bell relaxes, the second
vortex ring rolls under it and starts to spin faster. This sucks in
water which pushes up against the centre of the jellyfish and gives
it a secondary boost... Maybe explanation of role of stopping
vortices in jellyfish locomotion is easier to understand in Gemmel
(and Yong)?
Slide 13
Phylum Mollusca Shell is a skeleton that doesnt function in
locomotion. Snail body, visceral mass and foot, seems amorphous;
these animals are shape-shifters (octopus reknowned for escaping
cages through cracks): versatility in body shape change marks the
importance of its hydraulic skeleton: its use of fluid force
translocation in moving about: changing body shape by the
interaction of fluid and muscle and collagen fibres Land snail
Slide 14
A mollusc ancestral to squids, to see how foot shell &
mantle cavity changed during evolution
Slide 15
streamlining dorsal view Shell is an internal remnant sunk
within the mantle tissue; it is called the pen
Slide 16
Funnel (not visible in this photo) developed from posterior of
primitive foot. Primitive ventral surface of ancestor became
functional anterior end. Chromatophores are pigment cells in skin,
circlet of smooth muscle cells, disperse concentrate. Class
Cephalopoda includes squid, octopus, cuttlefish, Nautilus primitive
dorsum Fins set up waves; posterior lateral fins act as stabilizers
and rudders; squids achieve greatest swimming speeds of any aquatic
invertebrate, up to 40 kmph.
Slide 17
Assigned reading: Gosline J.M., & Demont M.E. 1984.
Jet-propelled swimming in squids. Scientific American 252: 96-103.
A swimming squid takes up and expels water by contracting radial
and circular muscles in its boneless mantle wall. Elastic collagen
springs in the muscle increase the power of the jet. Beware
potential confusion: squids jet-propel themselves and of course
there is a fluid-filled cavity involved the mantle cavity. The
seawater in this cavity functions in locomotion by virtue of its
high bulk modulus; if the seawater were not incompressible the
jetting wouldnt work. But this cavity is NOT functioning as a
hydrostatic skeleton antagonizing mantle muscles. Rather the mantle
wall itself is a muscular hydrostat.
Slide 18
The seawater within the mantle cavity of the squid is not
functioning as a hydrostatic skeleton. But it is the basis of the
animal's jet propulsion, which in turn depends upon the
incompressibility of seawater. When the radial muscles of the
mantle contract, the volume of the mantle cavity is increased and
seawater is drawn in. When the circular muscles of the mantle
contract, the volume of the mantle cavity is decreased and seawater
is squirted out. The action-force of the jetted seawater creates a
reaction force that pushes the squid in the opposite direction:
opposite to whatever direction the funnel is pointing. One-way
valves* control intake of water into mantle cavity at sides.
Pressure build up in seawater inside mantle cavity (circulars
contract) forces the inner flaps of the funnel against the mantle
wall water jets out funnel (hypostome). [*recall starfish
canals]
Slide 19
In the mantle structures interact: 1) collagen fibres make a
tunic that prevents longitudinal dimension change 2) radial muscles
contract to thin the mantle wall and 3) circular muscles of the
mantle contract to thicken the wall. Circulars and radials are
antagonists. The mantle (the actual wall) is a muscular hydrostat
and its volume must stay constant (just as if it were a
fluid-filled cavity). But (per Kier) the fibres are very critical:
because of the collagen tunic the mantle cannot get longer in the A
to B dimension: it can change in girth. [Imagine as it isnt: no
tunic: would lengthen in response to circulars.] A B
Slide 20
1.Radial muscles contract to cause: hyperinflation: seawater
intake into mantle cavity: outside diameter of mantle increases by
approximately 10% over resting diameter (girth increase); cavity
volume increases 22% re relaxed volume, wall thins. 2. Circular
muscles contract to bring mantle to about 75% of its relaxed
diameter, radials restored to precontracted length (girth
decrease): volume drops & pressure rises sharply, forcing the
inlet valvesl against the mantle wall and leaving only the funnel
as exit. relaxed Mantle wall Escape Jet Cycle of squid Internal
organs contracted
Slide 21
The mantle wall functions as a muscular hydrostat -- a
fluid-based skeleton [muscles mostly water] without a distinct
fluid chamber -- it makes antagonists of the radial and circular
muscles: contraction of one kind of muscle restores the other to
its relaxed state via this type of fluid skeleton. The radial and
circular muscles become coupled as antagonists by virtue of their
own tissue being significantly water and so incompressible and
because the mantle cannot lengthen. Because the mantle is
incompressible it must retain an overall constant volume; and it
cannot get longer as mantle muscles contract because of the
collagen fibre tunic that prevents any movement in that direction.
Thus, it can only increase or decrease in thickness at the same
time changing its overall diameter and the capacity of the mantle
cavity. When the radials contract the mantle walls must get thinner
and the walls move apart -- to maintain hydrostat volume.
Conversely when the circulars contract the mantle wall must get
thicker as the overall outside diameter of the mantle decreases. If
there were no inextensible fibres, if the animals mantle was not in
a jacket of fibres preventing it from lengthening, then the radials
and the circulars could not have an antagonistic effect on each
other.