Functional morphology of the feeding apparatus in chain pickerel, Esox niger: Adaptations for manipulation and consumption of large live prey

Prey processing is a vital component of predation and includes techniques such as cutting, shearing, and crushing. However, when prey is swallowed whole, processing can include holding and repositioning for optimal swallowing. The prey processing mechanism of fish like chain pickerel, Esox niger, appears unique to the members of the Esox genus. Following ambush and capture, pickerel processes large prey by “walking” its jaws along the prey’s body until its head is reached. Once there, prey is swallowed head-first. The mechanism used by pickerel to “walk” its jaws along the body of its prey occurs while the prey is still alive and struggling. This is paradoxical, as pickerel appear to be holding onto prey to prevent escape yet simultaneously letting go to reposition it for swallowing. Here we explore morphological adaptations facilitating the pickerel prey processing mechanism. Potential similarities to the prey processing mechanism of snakes are discussed, as this form of processing appears similar to the pterygoid walk snakes perform as a “hands-free” way of moving their jaws along prey. Additionally, the musculoskeletal components of pickerel are compared to that of largemouth bass, Micropterus salmoides, through dissection, manual manipulation, quantification of muscle architecture, and leverage analysis. Bass feed on similar prey but use water pressure to capture and position prey for swallowing. Anatomical differences in feeding structures suggests specialization for the mechanisms used by each species. Lastly, given a better understanding of the functioning of the prey processing mechanism of pickerel, potential applications to biomimetic tool design are discussed.