Adaptations to cursoriality and digit reduction in the forelimb and hind limb musculature of the African wild dog (Lycaon pictus)


SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
2021 VIRTUAL ANNUAL MEETING (VAM)
January 3 – Febuary 28, 2021

Meeting Abstract


14-3  Sat Jan 2  Adaptations to cursoriality and digit reduction in the forelimb and hind limb musculature of the African wild dog (Lycaon pictus) Smith, HF*; Adrian, B; Koshy, R; Alwiel, R; Wright, W; Grossman, A; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ hsmith@midwestern.edu http://www.midwestern.edu//academics/our-faculty/heather-smith-phd.xml

The African wild dog, Lycaon pictus, is native to southern and eastern Africa, and is unique among canids in its purported tetradactyly, nomadic lifestyle, and distinct reliance on exhaustive predation. This cursorial behavior and lack of a fully formed digit I presumably alter the structure, position, and functions of limb musculature. We conducted dissections and quantitative data collection of forelimb and hind limb myology of L. pictus, including descriptions, photographs, muscle maps and quantitative analyses. In L. pictus , muscles involved in forelimb posture and stability, and those that store elastic energy, have enlarged bony attachments. It has smaller wrist rotators than other carnivorans, likely to increase antebrachial stability over rotatory movement. While a full developed digit I is absent, we discovered a vestigial metacarpal I, resulting in changes to pollical muscle insertions, which may help stabilize the carpus during long distance locomotion and provide proprioception. In the hind limb, quadriceps femoris muscles were separated, which may allow a functional decoupling of hip flexor and stifle extensor components of thigh musculature, such that tensor fascia latae + rectus femoris flex the hip while the vasti extend the stifle to facilitate energy conservation during prolonged locomotion. Crural musculature was heavily invested in fascia and an extra gracilis tendon was present. Reductions and altered attachments of tibialis and fibularis muscles suggest reduced leverage during inversion/eversion and greater emphasis on stability of talocrural joint.

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