Musculoskeletal anatomical changes that accompany limb reduction in lizards

Author(s)

Abdala, Virginia ^[1] ; Grizante, Mariana B. ^[2] ; Diogo, Rui ^[3] ; Molnar, Julia ^[4] ; Kohlsdorf, Tiana ^[2]

Affiliation

^[1] CONICET UNT, Inst Biodiversidad Neotrop, RA-4000 San Miguel De Tucuman - Argentina

^[2] Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Biol, Ribeirao Preto, SP - Brazil

^[3] Howard Univ, Coll Med, Dept Anat, Washington, DC 20059 - USA

^[4] Coastal Carolina Univ, Dept Biol, Conway, SC 29526 - USA

• Document type: Journal article
• Source: Journal of Morphology; v. 276, n. 11, p. 1290-1310, NOV 2015.
• Web of Science Citations: 7

Abstract

Muscles, bones, and tendons in the adult tetrapod limb are intimately integrated, both spatially and functionally. However, muscle and bone evolution do not always occur hand in hand. We asked, how does the loss of limb bones affect limb muscle anatomy, and do these effects vary among different lineages? To answer these questions, we compared limb muscular and skeletal anatomy among gymnophthalmid lizards, which exhibit a remarkable variation in limb morphology and different grades of digit and limb reduction. We mapped the characters onto a phylogeny of the group to assess the likelihood that they were acquired independently. Our results reveal patterns of reduction of muscle and bone elements that did not always coincide and examples of both, convergent and lineage-specific non-pentadactyl musculoskeletal morphologies. Among lineages in which non-pentadactyly evolved independently, the degree of convergence seems to depend on the number of digits still present. Most tetradactyl and tridactyl limbs exhibited profound differences in pattern and degree of muscle loss/reduction, and recognizable morphological convergence occurred only in extremely reduced morphologies (e.g., spike-like appendix). We also found examples of muscles that persisted although the bones to which they plesiomorphically attach had been lost, and examples of muscles that had been lost although their normal bony attachments persisted. Our results demonstrate that muscle anatomy in reduced limbs cannot be predicted from bone anatomy alone, meaning that filling the gap between osteological and myological data is an important step toward understanding this recurrent phenomenon in the evolution of tetrapods. J. Morphol. 276:1290-1310, 2015. (c) 2015 Wiley Periodicals, Inc. (AU)

• FAPESP's process: 11/18868-1 - Evolution of meristic and morphometric diversity in the Autopodium of Squamata: patterns, processes and mechanisms
• Grantee: Tiana Kohlsdorf
• Support Opportunities: Regular Research Grants
• FAPESP's process: 10/00447-7 - Convergent morphological evolution in Squamata: developmental modularity and body elongation patterns
• Grantee: Mariana Bortoletto Grizante
• Support Opportunities: Scholarships in Brazil - Doctorate