Jan. 25, Lecture 7 Squid mantle hydrostat Asterias tube feet;
pulsate jet propulsion jellyfish Body waves: Nereis parapodia Snake
locomotion Adhesive locomotion: gastropods The term test short
answer scheduled for lecture time period on February 17, just
before Reading Week
Slide 2
Last years two-way table re mantle function: there is an error:
Volume decreases to 75% of relaxed volume: should be 75% of relaxed
diameter The essence of last lectures account of the squid mantle
as muscular hydrostat: the collagen creates a tunic that prevents
change in dimension in all longitudinal planes; this means that
radial and circular muscles are now efficient antagonists, one able
to stretch the other back to its precontracted state. Imagine it as
it isnt to better understand the effect: imagine no collagen.
Contract the radial muscles and normally the mantle thins. But
without the longitudinal restriction imposed by collagen it is not
as necessary to thin. The connective tissue collagen is a critical
element in the design. the most abundant protein in mammals, making
up about 25% to 35% of the whole-body protein content. Collagen, in
the form of elongated fibrils, is mostly found in fibrous tissues
such as tendon, ligament and skin, and is also abundant in cornea,
cartilage, bone, blood vessels, the gut, and intervertebral disc.
[from Wikkipedia]
Slide 3
From Brown, Selected Invertebrate Types
Slide 4
A parallel to the squid mantle: spiral connective tissue limits
response planes of structure and is essential for protraction
Slide 5
Santos, R. et al. 2005. Adhesion of echinoderm tube feet to
rough surfaces. J. exp. Biol. 208: 2555-2567. Fig. 6 external
morphology of unattached pedal discs of Paracentrotus lividus
(left) [sea urchin] and Asterias rubens [starfish] (right). End of
extensible cylinder is the disc, larger in diameter than the stem.
There is a central depression. The epidermis of the disc contains
glands which produce two secretions: glue/bonder and de-bonder,
i.e., adhesive secretions and de-adhesive secretions. The glue is
delivered through the disc cuticle to the substratum where it forms
a thin film bonding the foot. The debonding secretions are released
within the cuticle [how?] and act as enzymes; detaching the upper
coat of the glue and leaving the rest of the adhesive material
behind attached to the substratum as a footprint.
Slide 6
Pulsate jet swimming in jellyfish: pushes it in opposite
direction of jet; cancellation parallel to destructive interference
in sound production ? Polyp and medusa morphs Power and recovery
strokes Incompressible fluid displaced: jetting seawater out from
under umbrella Radial and circular fibres of myoepithelium;
Antagonist MESOGLEA Stores elastic strain energy like ligament of
scallop.
Slide 7
From Wikkimedia Commons pictures by Hans Hillewaert Nereis
succinia epitoke of polychaete worm
Slide 8
Retrograde vs direct body waves Errant polychaetes, parapodia;
aciculum [small pin] Circular oblique retractor (antagonist not
another muscle: but coelomic fluidand longitudinal muscles,
fenestrated septa Notopodium, neuropodium [noto = back] Nereis
parapodia:
Slide 9
Body waves and parapodia interact complexly Parapodia, kept
normal to the side of the segment and following the curve of the
body wave, if they are on the outside of a body wave, move through
a greater sweep of distance and develop more force against the
water than those on the opposite inside of the wave. The propulsive
forces produced are greater for parapodia on the outside of the
curve. The worm accentuates the difference by parapodium retraction
on the inside of the wave. BODY WAVE HEAD TO TAIL (like a fish):
outside parapodia (on the outside of the curve and developing more
force against the water are now sweeping forward toward the head
which will tend to propel the worm backward. BODY WAVE TAIL TO
HEAD: the more effective parapodia (on the outside of the curve now
sweep backward toward the tail which will tend to propel the worm
head-first. To make forward progress Nereis must use a direct body
wave and not a retrograde one the opposite of a fish.
Slide 10
sidewinder
Slide 11
Crotaline movement in snakes Only when certain portions of the
body wave are in contact with the substratum
Slide 12
Pedal locomotion in Gastropoda From Wikimedia Commons Arion
ater, black slug