4/16/2023 0 Comments Labchart reader event markers![]() There is indirect evidence of elastic energy storage in the jaw system during food capture from earlier work on the tiger salamander ( Ambystoma tigrinum) Reilly & Lauder used electromyography (EMG) to demonstrate that the adductor mandibulae internus (AMi) was activated approximately 20–30 ms prior to the onset of jaw-closing during the strike. As the food is processed, interactions of the jaw and the adductor musculature with food substrates that have different mechanical properties may influence the generation of reaction forces and the potential for elastic recoil action. ![]() Thus, while elastic recoil has been shown to confer benefits during the fast, gape-expansive behaviours involved in food capture, we suspect that elastic recoil may also be beneficial during the slower, gape-compressing movements involved in food processing. Food might escape the jaws of a predator if gape is prolonged following a strike, but the escape risk remains during food processing. Here, we probe the idea that elastic recoil might be important during aquatic food processing, where high viscosity and drag limit the speed at which elements such as jaws or fins can move. Several studies have questioned the utility of elastic recoil action in small animals and fluid-based movement, whereas others have discovered evidence of elastic action in flight and swimming. Elastic action has the ability to amplify movement speed with respect to the initial shortening speed of activated muscle fascicles and may, therefore, potentially help minimize jaw gape duration, which in turn minimizes prey escape risks. Nevertheless, we have fewer clear examples of elastic recoil action for feeding, despite the tendency of jaw systems to operate rapidly and powerfully. There are many prominent connective tissue sheets associated with the jaw musculature of most tetrapods, and especially basal aquatic-feeding anamniotes. The occurrence and utility of springs in feeding systems could potentially be as diverse as in limbs. By contrast, we have a relatively limited knowledge about biological springs in feeding and fluid-based motion systems. Our fairly detailed understanding of biological spring performance is to an overwhelming extent sourced from terrestrial limb systems. the upstroke phase of a wing flap or the swing phase of a limb stride. The latter can be accomplished as elastic stretch and recoil relegates the production of muscular force and work to recovery phases within the motion cycle where stress is low, e.g. Elastic recoil action may also reduce the need for muscles to do mechanical work by recycling gravitational-potential energy from joint movements, thereby improving movement economy. Biological springs are known to amplify the power of movement, as well as the rate at which kinetic energy is released from muscle contraction to power joint movement. The elastic action of biological springs is common across vertebrate locomotor systems, where stretch and recoil of compliant tissues including tendons and fascia play diverse roles. Amplification of jaw-closing speed resulting from elastic recoil likely confers ecological advantages in reducing prey escape risks during food processing in a dense and viscous fluid environment. These data demonstrate a clear role for elastic recoil, which may be unexpected for a MTU in a feeding system of a small, aquatic animal. The speed of MTU shortening, which dictates the speed of gape closing is 2.5–4.4 times greater than the speed of the initial shortening of the muscle fascicles for fish and cricket gape cycles, respectively. Activation lasts significantly shorter for fish than cricket processing, and muscle shortening during MTU lengthening yields significantly greater elastic strain for cricket processing. The muscle is pre-activated coincident with gape opening, which causes MTU stretch. We measure activation of the adductor mandibulae externus via electromyography and strain of the jaw adductor muscle–tendon unit (MTU), and gape kinematics via fluoromicrometry. Here, we ask if elastic recoil amplifies the speed of gape closing during aquatic food processing in the Axolotl ( Ambystoma mexicanum). However, less is known about elastic recoil action in feeding systems, particularly for small aquatic animals. Tendon springs often influence locomotion by amplifying the speed and power of limb joint rotation.
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