Lecture 9, Feb 1, 2011

Flea jump continuedLevers

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

Rebound resilience of the proteinresilin is 97%Bubonic plague flea: 1-2 mm long jumps 90 mm high6’ human to 300 feetFlea can jump >50 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.

An antagonist of the trochanteral depressor is the levator of the trochanter. It originates on the

inner wall of the coxa and inserts on the trochanter posterior to the axis. And another muscle antagonistic to

the trochanteral depressor is the epipleural muscle: this inserts on

the base of the coxa and on its contraction, as with the levator,

pulls behind the axis of rotation of the trochanter on the coxa. Both the epipleural muscle and the levator of

the trochanter have the effect of flexing the limb, i.e. raising it from

the substratum.

Under normal locomotory movement either the levator or the depressor is contracting: they are not active at the same moment. But in preparing itself in the jumping position, the flea eventually contracts all three muscles simultaneously.It begins by flexing the limb (the levator and epipleural muscles playing an appropriate part in this). Then all three muscles [levator of trochanter, epipleural muscle and depressor of the trochanter] are contracted simultaneously. Since the depressor opposes the action of the other two, nothing happens now to change the relation of the segments of the flexed hind limb. Rather the force expended by the muscles is "loaded into the pleural arch", i.e. it goes to compress the resilin pad located above the pleural plate, squeezing the resilin between the plate and the notum.

Some animals have two valves but are not Mollusca, e.g., lampshells

Discovering FossilsVenericor bivalve

Museum of New Zealand

Lampshell [Brachiopoda]

Bivalve (Mollusca) body Orientationpaleo.cortland.edu

Dragonfly flight muscles

Photo from ‘Creative Lynx’

Saltatorial adaptationAn unnamed Myopophyllum sp. of katydid from Ecuador

hind femur bears defensive spines: these legs are weapons as well as a device for rapid escape [see species on webpage home: it is the same genus]