Lecture 8, Jan. 27

ScutigeraAdhesive locomotion: walking on glue -- sliding on snot

Sidewinding and serpentine snakesFish swimming shapes

Jumping onto dogs

Arthropod of the day: Class Chilopoda: house centipede

Legs moved in a metachronal stepping wave: one step-cycles after another -- just out of phase;opposite is a synchronal wave: all in synchrony.The movement of Nereis parapodia during swimming is metachronal.

sidewinders Only certain portions of the bodywave are placed in contact with the substratum

Crotaline movement in snakes

What would happen when a crotaline snake tried to employ sidewinding in water?

The snake puts down body ‘segments’ at B and lifts them up at A [tractor]; the snake is not sliding its ‘segments’ along the ground

Fish swimming

Webb, Paul W. 1984. Form and functionin fish swimming. Scientific American 251: 58-68.Sfakiotakis M., Lane D.M., Davies J.B.C. 1999. Review of fish swimming modes for aquatic locomotion. IEEE Journal of Oceanic Engineering 24: 237-252

Thrust: forces that tend to advance the fish; drag: forces that tend to retard it

Retrograde body wave pushes back againstthe water; creates a reaction force resolvableinto two components: one lateral and the other propelling the animal forward: thrust; lateral forces of the right and left sides tend to cancel out.Propulsive element: small segment of bodyInclination of reaction force is toward the headThe farther back a propulsive element is located the steeper this incline toward the head; thus more of the reaction force is thrust as one moves posteriorly out along the tail.Rearward elements are moving through a greater displacement – in the same time – so they needs must go faster.

Change medium to ‘pegs’: snake locomotion serpentine on land

Undulation and oscillation; ribbon fin;feathering, draw strokes, flexible canoe paddle. In oscillation a fin attached by a short peduncle (base) moves rapidly back and forth to propel without any wave motion.

Diversity of fish body shapes relate to locomotion: corners of the triangle: tuna sustained cruising, strong ‘narrow necking’; butterfly fish for maneuvering, plate in water; pike or barracuda for acceleration.

Pedal locomotion in Gastropoda

From Wikimedia CommonsArion ater, black slug

Mantle cavity has been converted into a lung: hence ‘pulmonate snails’ of which slugs are just one type; edges of mantle cavity sealed to back except for pneumostome opening; roof of mantle cavity vascularized, no gill. >16000 species.

Denny, M. 1980. The role of gastropod pedal mucus in locomotion. Nature 285: 160-161. See also: Barnes, Invert. Zool.

7th ed, p. 363.

Monotaxic and ditaxic species

• The schnauzer and the blood-sucking ectoparasite

Adaptiveness of flea side-to-side body flattening; flea setae (hairs) orientation

Rothschild, M. et al. 1973. The flying leap of the flea. Scientific American 222: 92-101

Rebound resilience of the proteinresilin is 97%Fleas can jump 100 X its body lengthAccelerates from rest to 1 metre p secin a distance of 0.4 mm; extends its legs in about 8/1000 th of a second.

Power rate of doing workResilin located in the pleural archEnergy loaded into pleural arch and held there by catchesRelease is by body width change.

• The trochanteral depressor is located a relatively long way from the trochanter; it originates on the notum and inserts on the trochanter (B, C). The insertion is via a massive tendon-like apodeme and this attaches anterior to the (dicondylic) axis of the trochanteral rotation (see blue dots in A, B, C). So the contraction of the trochanteral depressor pulls the trochanter, rotating it forward on the coxa and extending it (= depressing it) against the substratum.