Extremely fast prey capture in pipefish is powered by elastic recoil

Abstract

The exceptionally high speed at which syngnathid fishes are able to rotate their snout towards prey and capture it by suction is potentially caused by a catapult mechanism in which the energy previously stored in deformed elastic elements is suddenly released. According to this hypothesis, tension is built up in tendons of the post-cranial muscles before prey capture is initiated. Next, an abrupt elastic recoil generates high-speed dorsal rotation of the head and snout, rapidly bringing the mouth close to the prey, thus enabling the pipefish to be close enough to engulf the prey by suction. However, no experimental evidence exists for such a mechanism of mechanical power amplification during feeding in these fishes. To test this hypothesis, inverse dynamical modelling based upon kinematic data from high-speed videos of prey capture in bay pipefish Syngnathus leptorhynchus, as well as electromyography of the muscle responsible for head rotation (the epaxial muscle) was performed. The remarkably high instantaneous muscle-mass-specific power requirement calculated for the initial phase of head rotation (up to 5795 W kg K1 ), as well as the early onset times of epaxial muscle activity (often observed more than 300 ms before the first externally discernible prey capture motion), support the elastic power enhancement hypothesis.

Comparative feeding kinematics and performance of odontocetes: belugas, Pacific white-sided dolphins and long-finned pilot whales

“…Results from previous mammalian suction performance studies indicate that faster hyolingual and jaw kinematics are associated with suction (Kastelein et al, 1997;Werth, 2000a;Bloodworth and Marshall, 2005;Marshall et al, 2008). This relationship is also prominent among teleosts, with an extreme case represented by sygnathids (de Lussanet and Muller, 2007;Van Wassenbergh et al, 2008;Van Wassenbergh et al, 2009). However, in this study, belugas exhibited some kinematics that were more similar to ram feeding bottlenose dolphins, and that may result from a suite of varied morphological and behavioral specializations for suction generation in belugas.…”

An adaptive explanation for the horse-like shape of seahorses

“…We expected the head-to-trunk position to have a biomechanical role during pivot feeding of seahorses because of an observation during previous research on the bay pipefish Syngnathus leptorhynchus 7 . In that species, a considerable ventral countermovement of the trunk occurred when the head was rotated dorsally towards the prey.…”

“…As suction only works within a relatively short distance of the mouth 5,6 , bringing the mouth quickly close to the prey by rotating the head is critical to prevent prey from escaping. Syngnathid fishes (seahorses, pipefish and seadragons) are therefore equipped with large tendons of the epaxial muscles, in which they store and release elastic energy that accelerates the head towards the prey in astonishingly little time ( < 0.005 s) 7,8 .…”

Jaw protrusion enhances forces exerted on prey by suction feeding fishes

“…In fact, any behaviour that will rapidly shorten the distance between the prey and the predator while suction is being produced might have similar effects on the force exerted on the prey. Such behaviours include forward swimming (ram), fast cranial elevation (Van Wassenbergh et al 2008) or feeding on prey that is drifting in a current towards the predator, as done by many site-attached coral reef planktivores (Coughlin & Strickler 1990;Westneat 2006). These behaviours are not mutually exclusive to jaw protrusion (at least mechanically) and would have an additive effect on the force and the capture success.…”

“…Moreover, the magnitude of increased force depends also on the speed of jaw protrusion (figures 3 and 4), and jaw protrusion can attain very high speeds (Lauder 1982;Motta 1984;Van Leeuwen & Muller 1984;Osse 1985) that allow significant augmentation of forces on the prey. It is probable that the rapid head rotation during feeding in pipefishes (Van Wassenbergh et al 2008) also augments the forces these fishes exert on their prey.…”