Differing effects of size and lifestyle on bone structure in mammals

Amson, Eli; Bibi, Faysal

doi:10.1101/2020.08.13.249128

Cited by 9 publications

(26 citation statements)

References 78 publications

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“…3 c ). This is evidently a modification that has to be associated with diaphysis elongation, which is indeed found in all aerial mammals (Amson & Bibi 2020), even though their convergence was found as “incomplete” (Grossnickle et al. 2020).…”

Section: Discussionmentioning

confidence: 90%

“…A dataset of 159 specimens of extant mammals (adult, disease‐free, and wild‐caught) was built to comprise representatives of each independent acquisition of specialised lifestyles [fully aquatic (Howell 1930), aerial (Jackson & Thorington 2012), and subterranean (Ellerman 1956)], as well as terrestrial close relatives (figure 1; Amson and Bibi 2020). This was complemented with five extinct taxa with well‐preserved humerus: the chiropteran Hipposideros (Pseudorhinolophus) “antiquus” (MB.Ma.27298; late Eocene, Escamps, phosphorites du Quercy, France (Maitre 2014)), Palaeonycteris robustus (MB.Ma.27309; Early Miocene or possibly late Oligocene (De Pietri et al.…”

Section: Methodsmentioning

confidence: 99%

“…I used the extant species timetree from TimeTree.org (Kumar et al. 2017), modifying it according to the sampled species as detailed in Amson and Bibi (2020) (provided in the File S1, available online). When several specimens of the same species were sampled, their slopes were averaged.…”

Section: Methodsmentioning

confidence: 99%

“…During the evolution of therian mammals, some linages acquired adaptions to highly specialised lifestyles. The aerial, fully aquatic, and subterranean lifestyles, in particular, were acquired by clades with extant representatives seven times (among which three in the Petauroidea), two times, and 13 times, respectively (Amson & Bibi 2020). I sampled several extant representatives of each of these clades, along with terrestrial species spread across the tree of therian mammals, using high resolution micro‐Computed Tomography (μCT).…”

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confidence: 99%

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Humeral diaphysis structure across mammals

Amson

2021

Evolution

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Long bones comprise articular ends (epiphyses) joined by transitional metaphyses and a diaphysis (shaft). The structure of the latter is often viewed as regularly tubular across tetrapods (limbed vertebrates). However, assessments of the bone structure along the whole diaphysis are rare. Here, I assess whole-diaphysis profiles of global compactness (bone fraction) of 164 species of extant and extinct therian mammals (marsupials + placentals) in a phylogenetically informed context. Generally terrestrial, mammals have acquired multiple times the highly specialized aerial, fully aquatic, and subterranean lifestyles, allowing to potentially associate specific traits with these lifestyles. I show that there is a consistent increase in global compactness along the diaphysis in most mammals. This pattern is modified in a limited number of specialized species: all aerial clades (gliders and bats) have rather uniform and low values, while cetaceans' humeral diaphysis is marked by a slightly more compact mid-diaphyseal region. Among subterranean clades, structure alterations are most obvious in fossorial talpids (true moles) and their highly modified humerus. These results call for the investigation of bone structure in whole skeletal elements of key fossils in order to reconstruct the patterns of evolutionary modifications associated with lifestyle transitions.

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Section: Discussionmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Humeral diaphysis structure across mammals

Amson

2021

Evolution

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“…The final, altered tree (182 species) can be found on figshare [104]. Lifestyle classification of all genera and timetree with 182 sampled species can also be found on figshare [104].…”

Section: Lifestyles Species and Treementioning

confidence: 99%

Differing effects of size and lifestyle on bone structure in mammals

Amson

Bibi

2021

BMC Biol

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Background Mammals are a highly diverse group, with body mass ranging from 2 g to 170 t, and encompassing species with terrestrial, aquatic, aerial, and subterranean lifestyles. The skeleton is involved in most aspects of vertebrate life history, but while previous macroevolutionary analyses have shown that structural, phylogenetic, and functional factors influence the gross morphology of skeletal elements, their inner structure has received comparatively little attention. Here we analysed bone structure of the humerus and mid-lumbar vertebrae across mammals and their correlations with different lifestyles and body size. Results We acquired bone structure parameters in appendicular and axial elements (humerus and mid-lumbar vertebra) from 190 species across therian mammals (placentals + marsupials). Our sample captures all transitions to aerial, fully aquatic, and subterranean lifestyles in extant therian clades. We found that mammalian bone structure is highly disparate and we show that the investigated vertebral structure parameters mostly correlate with body size, but not lifestyle, while the opposite is true for humeral parameters. The latter also show a high degree of convergence among the clades that have acquired specialised (non-terrestrial) lifestyles. Conclusions In light of phylogenetic, size, and functional factors, the distribution of each investigated structural parameter reveals patterns explaining the construction of appendicular and axial skeletal elements in mammalian species spanning most of the extant diversity of the clade in terms of body size and lifestyle. These patterns should be further investigated with analyses focused on specific lifestyle transitions that would ideally include key fossils.

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Effect of captivity on the vertebral bone microstructure of xenarthran mammals

Zack

Smith

Angielczyk

2021

The Anatomical Record

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Captive specimens in museum collections facilitate study of rare taxa, but the lifestyles, diets, and lifespans of captive animals differ from their wild counterparts. Trabecular bone architecture adapts to in vivo forces, and may reflect interspecific variation in ecology and behavior as well as intraspecific variation between captive and wild specimens. We compared trunk vertebrae bone microstructure in captive and wild xenarthran mammals to test the effects of ecology and captivity. We collected μCT scans of the last six presacral vertebrae in 13 fossorial, terrestrial, and suspensorial xenarthran species (body mass: 120 g to 35 kg). For each vertebra, we measured centrum length; bone volume fraction (BV.TV); trabecular number and mean thickness (Tb.Th); global compactness (GC); cross‐sectional area; mean intercept length; star length distribution; and connectivity and connectivity density. Wild specimens have more robust trabeculae, but this varies with species, ecology, and pathology. Wild specimens of fossorial taxa (Dasypus) have more robust trabeculae than captives, but there is no clear difference in bone microstructure between wild and captive specimens of suspensorial taxa (Bradypus, Choloepus), suggesting that locomotor ecology influences the degree to which captivity affects bone microstructure. Captive Tamandua and Myrmecophaga have higher BV.TV, Tb.Th, and GC than their wild counterparts due to captivity‐caused bone pathologies. Our results add to the understanding of variation in mammalian bone microstructure, suggest caution when including captive specimens in bone microstructure research, and indicate the need to better replicate the habitats, diets, and behavior of animals in captivity.

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Differing effects of size and lifestyle on bone structure in mammals

Cited by 9 publications

References 78 publications

Humeral diaphysis structure across mammals

Humeral diaphysis structure across mammals

Differing effects of size and lifestyle on bone structure in mammals

Effect of captivity on the vertebral bone microstructure of xenarthran mammals

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