Common cellular origin and diverging developmental programs for different sesamoid bones

Eyal, Shai; Rubin, Sarah; Krief, Sharon; Levin, Lihi; Zelzer, Elazar

doi:10.1242/dev.167452

Cited by 35 publications

(57 citation statements)

References 45 publications

(64 reference statements)

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“…Consequently, differences among species in the association of the calcar with the calcaneus may be the result of relatively minor developmental alterations. Our finding of many sesamoids in bat feet, consistent with a recent assessment of bat sesamoids (Amador et al 2018), suggests a propensity for metaplastic cartilage and bone development in bat feet, as tendon metaplasia is hypothesized to play a role in sesamoid development (Sarin et al 1999; but see also Eyal et al 2015Eyal et al , 2019. Developmental plasticity may also lead to intraspecific variation in calcar anatomy or even presence.…”

Section: Discussionsupporting

confidence: 87%

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Anatomical diversification of a skeletal novelty in bat feet

2019

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Neomorphic, membrane‐associated skeletal rods are found in disparate vertebrate lineages, but their evolution is poorly understood. Here we show that one of these elements—the calcar of bats (Chiroptera)—is a skeletal novelty that has anatomically diversified. Comparisons of evolutionary models of calcar length and corresponding disparity‐through‐time analyses indicate that the calcar diversified early in the evolutionary history of Chiroptera, as bats phylogenetically diversified after evolving the capacity for flight. This interspecific variation in calcar length and its relative proportion to tibia and forearm length is of functional relevance to flight‐related behaviors. We also find that the calcar varies in its tissue composition among bats, which might affect its response to mechanical loading. We confirm the presence of a synovial joint at the articulation between the calcar and the calcaneus in some species, which suggests the calcar has a kinematic functional role. Collectively, this functionally relevant variation suggests that adaptive advantages provided by the calcar led to its anatomical diversification. Our results demonstrate that novel skeletal additions can become integrated into vertebrate body plans and subsequently evolve into a variety of forms, potentially impacting clade diversification by expanding the available morphological space into which organisms can evolve.

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Section: Discussionsupporting

confidence: 87%

“…; but see also Eyal et al. , ). Developmental plasticity may also lead to intraspecific variation in calcar anatomy or even presence.…”

Section: Discussionmentioning

confidence: 91%

Anatomical diversification of a skeletal novelty in bat feet

2019

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“…; Eyal et al. , ). It would be very interesting to test whether the progenitor cells of the TP are similar to those of other sesamoids, which would confirm these structures as those mainly responsible for the plasticity of the patterning of vertebrate skeleton.…”

Section: Discussionmentioning

confidence: 98%

“…Sesamoids have been proposed as a source of skeletal variability (Parsons, , ; Eyal et al. , ; V. Abdala, M. C. Vera, L. I. Amador, G. Fontanarrosa, J. Fratani & L. Ponssa, in prep.) and it could be inferred that they even can give rise to a digit‐like structure (see e.g.…”

Section: Discussionmentioning

confidence: 99%

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Functional morphology and identity of the thenar pad in the subterranean genus Ctenomys (Rodentia, Caviomorpha)

et al. 2019

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As in many other fossorial tetrapods, the most obvious adaptations to scratch‐digging in the subterranean tuco‐tuco (Rodentia, Ctenomyidae, Ctenomys) are found in the hands, which among other adaptations, present the mesaxonic condition; i.e. the central digits are more developed, and also their claws, which are curved and elongated. The thumb is atrophied and aligned with the rest of the digits, showing a small and flat claw. This configuration of digits and claws seems to be in accordance with what it is expected for rodents: rudimentary movements when handling food items. However, on the palmar side of the hand, tuco‐tucos have several pads, the thenar (located under the thumb) being the most developed. In this study, we investigated the functional morphology of the thenar pad through different approaches: musculoskeletal anatomy, histology and functionality. The analysis of radiographs and clarified and double‐stained hand samples of Ctenomys talarum and C. australis showed that the thenar pad is supported by a paddle‐shaped bone that articulates with a protrusion in the scapholunate bone. This bone, flat and long, continues in a flat cartilaginous structure, with a shape similar to a claw. Dissections showed that the thenar pad has several associated muscles: the m. palmaris longus, the m. abductor pollicis longus, and a massive muscular complex located between the thumb and the thenar pad. By topology it might be inferred that this complex is formed by the m. abductor pollicis brevis, the m. flexor pollicis brevis and the m. adductor pollicis brevis. Longitudinal histological sections of the thenar pad stained with hematoxylin‐eosin showed a thick layer of keratin at the distal end, external face. The observation of live specimens of C. talarum foraging on two food items of different size and filmed at 300 fps showed that the thenar pad acts as an opposable thumb, with digit‐like movements. Tuco‐tucos are able to perform more precise movements than expected, and to grasp and manipulate the food with one hand. In previous studies, it was suggested that the thenar pad was supported by a ‘palmar ossicle’, or ‘prepollex’ (= radial sesamoid bone). Our results suggest that this sesamoid underwent a radical change on its morphology, making the thenar pad a part of the food handling system in Ctenomys, so the thenar pad might be considered a ‘false thumb’, rather than a palmar pad. It is suggested to advance on the description and functional analysis of the thenar pad, redefining the structure, since the terms used so far to define it would not be accurate.

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The sesamoid bone in the long abductor muscle tendon of the first digit in the dog

Broeck

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Duchateau

et al. 2021

The Anatomical Record

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The sesamoid bone in the tendon of the m. abductor digiti primi longus is considered present in most dog breeds and is described to be radiologically detectable at the level of the carpus from the age of 4 months. However, an extensive investigation of this sesamoid bone has not been conducted before. The aim of this study was therefore to determine its prevalence in different dog breeds, to describe its histological development, and to determine the age at which it becomes radiologically visible. The prevalence of the sesamoid bone was assessed on radiographic images of the carpus or by dissection of the carpal region in 743 adult dogs of 115 breeds. Its development was studied by dissection and histological analysis in 45 puppies and its timing of radiological appearance was evaluated in 209 puppies. At least one sesamoid bone was present in all adult dogs, except for 14 dogs of six breeds of predominantly the small breed category. The lowest prevalence rate of 38.46% was exhibited in the French bulldog. The histological development could be divided into five stages. The first radiographic appearance corresponded to the coalescence of smaller ossification centers into one big nucleus (stage 4). The mean time of radiographic appearance was 108.4 days. This study provides extensive data on the prevalence and timing of the radiographic appearance of a sesamoid at the carpus of the dog. The data on radiographic appearance may be helpful in the age estimation of puppies.

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Common cellular origin and diverging developmental programs for different sesamoid bones

Cited by 35 publications

References 45 publications

Anatomical diversification of a skeletal novelty in bat feet

Anatomical diversification of a skeletal novelty in bat feet

Functional morphology and identity of the thenar pad in the subterranean genus Ctenomys (Rodentia, Caviomorpha)

The sesamoid bone in the long abductor muscle tendon of the first digit in the dog

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