The impact of digging on the evolution of the rodent mandible

McIntosh, Andrew; Cox, Philip G.

doi:10.1002/jmor.20929

Cited by 12 publications

(5 citation statements)

References 53 publications

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“…A notable ecological transition is represented by the colonization of the subterranean ecotope by different, unrelated taxa (rodents, insectivores and marsupials [12, 13]). Different studies on rodents have demonstrated how the colonization of the subterranean ecotope could dramatically influence species morphology and how digging specialization shapes the evolution of forelimbs and the cranio-dental complex [14–16]. One of the most spectacular examples of adaptation to subterranean life is represented by moles.…”

Section: Introductionmentioning

confidence: 99%

Impact of transition to a subterranean lifestyle on morphological disparity and integration in talpid moles (Mammalia, Talpidae)

et al. 2019

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Background Understanding the mechanisms promoting or constraining morphological diversification within clades is a central topic in evolutionary biology. Ecological transitions are of particular interest because of their influence upon the selective forces and factors involved in phenotypic evolution. Here we focused on the humerus and mandibles of talpid moles to test whether the transition to the subterranean lifestyle impacted morphological disparity and phenotypic traits covariation between these two structures. Results Our results indicate non-subterranean species occupy a significantly larger portion of the talpid moles morphospace. However, there is no difference between subterranean and non-subterranean moles in terms of the strength and direction of phenotypic integration. Conclusions Our study shows that the transition to a subterranean lifestyle significantly reduced morphological variability in talpid moles. However, this reduced disparity was not accompanied by changes in the pattern of traits covariation between the humerus and the mandible, suggesting the presence of strong phylogenetic conservatism within this pattern.

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Section: Introductionmentioning

confidence: 99%

Impact of transition to a subterranean lifestyle on morphological disparity and integration in talpid moles (Mammalia, Talpidae)

et al. 2019

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“…Although incisors are key to pigs’ detection and ingestion of foods, their functional morphology is largely inferred from studies in other species. For example, rodents using their incisors to dig have procumbent incisors that morphologically differ from rodents that do not dig with their incisors (Landry, 1957; McIntosh & Cox, 2016, 2019). This suggests that the horizontally protruding mandibular incisors in pigs may not only interact with diverse food textures and substrates during foraging but may also be used in digging.…”

Section: Discussionmentioning

confidence: 99%

In vivo measurement of strain in the periodontal space of pig (Sus scrofa) incisors using in‐fiber Bragg sensors

Popowics,

Hwang,

et al. 2024

Journal of Morphology

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The incisor teeth in pigs, Sus scrofa, function in association with a disc‐shaped snout to explore the environment for potential food. Understanding how mechanical loading applied to the tooth deforms the periodontal ligament (PDL) is important to determining the role of periodontal mechanoreceptors during food exploration and feeding. The objective of this study was to use fiber Bragg (FBG) sensors to measure strain in vivo within the PDL space of pig incisors. The central mandibular incisors of pigs underwent spring loaded lingual tipping during FBG strain recording within the labial periodontal space. FBG sensors were placed within the periodontal space of the central mandibular incisors of ~2–3‐month‐old farm pigs. The magnitude and orientation of spring loads are expected to mimic incisor contact with food. During incisor tipping with load calibrated springs, FBG strains in vitro (N = 6) and in vivo (N = 6) recorded at comparable load levels overlapped in range (−10–20 με). Linear regressions between peak FBG strains, that is, the highest recorded strain value, and baseline strains, that is, strain without applied spring load, were significant across all in vivo experiments (peak strain at 200 g vs. baseline, p = .04; peak strain at 2000 g vs. baseline p = .03; peak strain at 2000 g vs. 200 g, p = .004). These linear relationships indicate that on a per experiment basis, the maximum measured strain at different spring loads showed predictable differences. A Friedman test of the absolute value of peak strain confirmed the significant increase in strain between baseline, 200 g, and 2000 g spring activation (p = .02). Mainly compressive strains were recorded in the labial PDL space and increases in spring load applied in vivo generated increases in FBG strain measurements. These results demonstrate the capacity for FBG sensors to be used in vivo to assess transmission of occlusal loads through the periodontium. PDL strain is associated with mechanoreceptor stimulation and is expected to affect the functional morphology of the incisors. The overall low levels of strain observed may correspond with the robust functional morphology of pig incisors and the tendency for pigs to encounter diverse foods and substrates during food exploration.

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“…Compared to the other specimens in the study, and indeed many other rodents 9 , these two species exhibit far longer incisor roots relative to the amount of incisor protruding from the alveolus. Similarly, chisel-tooth digging rodents that require high bite forces to penetrate hard substrates have also been observed to possess incisors with notably deep roots 21 , 52 . The larger stress increases in these specimens may be reflective of a larger volume of tooth material that has been replaced by bone or air.…”

Section: Discussionmentioning

confidence: 99%

“…In rodents, the unerupted portion of the incisor typically extends distally to the end of the tooth row or just beyond 9 , occasionally extending as far as, or into, the condylar process 21 . It has previously been suggested that the deep internal projection of the incisor within the rodent mandibular body is responsible for the arch-like shape of the mandible visible in many rodents and a reduction in the bending moment by up to 25% compared to a beam-like mandible 3 , 22 .…”

Section: Introductionmentioning

confidence: 99%

The biomechanical significance of the elongated rodent incisor root in the mandible during incision

Morris

Cox

Cobb

2022

Sci Rep

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Rodents are characterised by a distinctive masticatory apparatus which includes a single pair of enlarged and continually growing incisors. This morphology, termed diprotodonty, has also independently evolved in a number of other mammals, including the aye-aye. This study examined the functional significance of the internal “root” of the elongated rodent-like incisor. The mandibles of four rodents and an aye-aye were modelled to exhibit incrementally shorter incisor roots. Finite element analysis was used to predict stress and strain patterns across the jaw to determine whether the length of the incisor root contributes to the resistance of mechanical forces encountered in the mandible during incision. It was found that von Mises stresses increase in the region of the mandible local to where the incisor is removed, but that the stress distribution across the wider mandible is only minimally affected. Thus, the long internal incisor appears to play a small role in resisting bending forces close to the incisor alveolus, and may act with the arch-like mandibular shape to strengthen the mandible in this region. However, the impact across the whole mandible is relatively limited, suggesting the highly elongate incisor in diprotodont mammals may be principally driven by other factors such as rapid incisor wear.

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The impact of digging on the evolution of the rodent mandible

Cited by 12 publications

References 53 publications

Impact of transition to a subterranean lifestyle on morphological disparity and integration in talpid moles (Mammalia, Talpidae)

Impact of transition to a subterranean lifestyle on morphological disparity and integration in talpid moles (Mammalia, Talpidae)

In vivo measurement of strain in the periodontal space of pig (Sus scrofa) incisors using in‐fiber Bragg sensors

The biomechanical significance of the elongated rodent incisor root in the mandible during incision

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