Comparative muscle anatomy of the anuran pelvis and hindlimb in relation to locomotor mode

Leavey, A; Richards, CT; Porro, LB

Abstract

Frogs have a highly conserved body plan, yet they employ a diverse array of locomotor modes, making them ideal organisms for investigating the relationships between morphology and locomotor function, in particular whether anatomical complexity is a prerequisite for functional complexity. We use diffusible iodine contrast-enhanced microCT (diceCT) imaging to digitally dissect the gross muscle anatomy of the pelvis and hindlimbs for 30 species of frogs representing five primary locomotor modes, including the first known detailed dissection for some of the world's smallest frogs, forming the largest digital comparative analysis of musculoskeletal structure in any vertebrate clade to date. By linking musculoskeletal dissections and phylogenetic comparative methods, we then quantify and compare relationships between anatomy and function across over 160 million years of anuran evolution. In summary, we have found that bone lengths and pelvic crest sizes are generally not reliable predictors of muscle sizes, which highlights important implications for future palaeontological studies. Our investigation also presents previously unreported differences in muscle anatomy between frogs specialising in different locomotor modes, including several of the smallest frog hindlimb muscles, which are extremely difficult to extract and measure using traditional approaches. Furthermore, we find evidence of many-to-one and one-to-many mapping of form to function across the phylogeny. Additionally, we perform the first quantitative analysis of how the degree of muscle separation can differ between frogs. We find evidence that phylogenetic history is the key contributing factor to muscle separation in the pelvis and thigh, while the separation of shank muscles is influenced more strongly by locomotor mode. Finally, our anatomical 3D reconstructions are published alongside this manuscript to contribute towards future research and serve as educational materials. Scientists at UCL and the Royal Veterinary College have digitally dissected the musculoskeletal anatomy of the pelvis and hindlimbs of 30 frog species using contrast-enhanced microCT scanning, forming the largest digital anatomical dataset in any vertebrate group to date. The team have discovered previously unreported anatomical differences between frogs specialising in different locomotor modes and have published all of the 3D anatomical reconstructions with detailed annotations, free for anyone to download.image

Citation

Leavey, A., Richards, C., & Porro, L. (2024). Comparative muscle anatomy of the anuran pelvis and hindlimb in relation to locomotor mode. Journal of Anatomy, https://doi.org/10.1111/joa.14122

• Journal Article Type: Article
• Acceptance Date: Jul 25, 2024
• Online Publication Date: Aug 9, 2024
• Publication Date: 2024
• Deposit Date: Aug 19, 2024
• Publicly Available Date: Aug 19, 2024
• Journal: Journal of Anatomy
• Print ISSN: 0021-8782
• Electronic ISSN: 1469-7580
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1111/joa.14122
• Keywords: diceCT; dissection; frog; imaging; locomotion; musculoskeletal; LEGGED RUNNING FROG; COMPUTED-TOMOGRAPHY DICECT; SOFT-TISSUE ANATOMY; JUMPING PERFORMANCE; FUNCTIONAL-MORPHOLOGY; DIGITAL DISSECTION; POWER OUTPUT; R PACKAGE; EVOLUTION; MUSCULATURE