SoOoOo, it has been a long time since my last post, but never fear: I have spent the last 6 months hard at work. Over the next few posts, I will let you know what is going on in our lab. This post is all about salamanders jumping and me dorking out.
When we last left our hero, the salamanders had been jumped under high-speed camera and subjected to various biomechanic analysis. We learned that their jump somewhat mimics a fish’s “C-start” escape response, and could only be initiated when the salamander was under duress (my finger). The salamander bends its torso into a C-shape and then rapidly unbends its torso, pivoting on its inside foot and catapults itself into the air. Their take-off velocities could reach as high as 1.2 m/s, which converts to 2.5 mph-ish…which sounds slow, but consider that they average about 6-10 cm long (including tail) and we are looking at an animal that that moves 15+ times its body length a second! You would be hard pressed to find a 6 foot man able to cross 90 feet (30ish meters) in that span. Even Usain Bolt (my man!) can only tackle up to maybe 14 meters a second. Therefore: Go salamanders!
On further review of their kinematics, it is clear that their jump is somewhat sloppy. This makes sense since these little guys are not arboreal (tree-livers), and so never need to jump from place to place, expect to frantically escape death, therefore natural selection would only favor just enough jumping ability to get away from their predators. (Though I would like to say a study on how they deal with falling through the air is underway!)
New Projects: My undergraduate researcher, Eileen Baker, and I are now focusing our efforts to understand where the energy for this jump comes from in the body. It is obvious that the quick bending and unbending of the torso plays a role in this…but what muscle supplies the power? Also, do the hips play a role in this launch? To make 2 months analysis short, yes, the hips play a pivotal role, by, well, pivoting around an inside planted foot (think of a catapult with the lever arm as the salamander leg and the rock being tossed as the body).
How much of a role does the hip play? We do not know yet.
How much of a role do the muscles play in the jump? We do not know.
Is there stored elastic energy in the muscles that accumulates during the bending phase of the jump and then expelled during the unbending phase (as is seen in human walking/running)? We do not know.
To answer these questions, we are going to jump our salamanders on a micro-force plate (thank you Dr. David Lee @UNLV for letting us borrow such a force plate), which after some nifty math work, should give us some answers to these questions.
Well that is the salamander saga, stay tune as new results pour in, and a lowly graduate student tries (and possibly fails) to make sense of it.