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Thomas VJ, Shaw J, Tay N, Warburton NM. Comparative three-dimensional jaw muscle anatomy of marsupial carnivores (Dasyurus spp.) and the termite-eating numbat (Myrmecobius fasciatus). J Morphol 2024; 285:e21684. [PMID: 38439588 DOI: 10.1002/jmor.21684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 12/14/2023] [Accepted: 02/21/2024] [Indexed: 03/06/2024]
Abstract
Among marsupials, the endangered numbat (Myrmecobius fasciatus) is the only obligate myrmecophage with a diet comprised strictly of termites. Like many other specialised myrmecophagous mammals, numbats have a gracile and highly specialised skull morphology with an elongated rostrum and small braincase. Myrmecobiidae is one of four taxonomic families within the Australasian marsupial order Dasyuromorphia, and to date, the muscular anatomy of any member of this group is relatively poorly known. We utilised microdissection and contrast-enhanced microcomputed tomography scanning to provide the first comprehensive qualitative and quantitative descriptions of jaw muscle anatomy in numbats and quolls (Dasuyrus species). The arrangement of the jaw muscles across these species was conservative, both in gross anatomy and muscle proportions, corresponding to a 'generalised' mammalian pattern. In contrast to Dasyurus, the jaw muscles of the numbat were greatly reduced. Many aspects of the muscle anatomy of the numbat were similar to patterns reported in other myrmecophagous species, particularly a greatly reduced temporalis muscle. Unusually, the digastric muscle in the numbat was comprised of a single, large anterior belly while the posterior belly was absent. We propose that the enlarged anterior belly of the digastric may be linked to jaw stabilisation and coordination of tongue movements during feeding. The lateral insertion and fascial connection of the digastric to the tongue in numbats may also aid in distributing stress evenly across the jaw and minimise muscle fatigue. The muscle descriptions and three-dimensional models provided in this study will facilitate further analysis of musculoskeletal adaptation and evolution within the Dasyuromorphia.
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Affiliation(s)
- Vanessa J Thomas
- School of Medical, Molecular and Forensic Sciences, Murdoch University, Murdoch, Australia
| | - Jeremy Shaw
- Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Australia
| | - Natasha Tay
- Centre for Terrestrial Ecosystem Science and Sustainability, Harry Butler Research Institute, Murdoch University, Murdoch, Australia
| | - Natalie M Warburton
- School of Medical, Molecular and Forensic Sciences, Murdoch University, Murdoch, Australia
- Centre for Terrestrial Ecosystem Science and Sustainability, Harry Butler Research Institute, Murdoch University, Murdoch, Australia
- Western Australian Museum, Welshpool, Australia
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Teullet S, Tilak MK, Magdeleine A, Schaub R, Weyer NM, Panaino W, Fuller A, Loughry WJ, Avenant NL, de Thoisy B, Borrel G, Delsuc F. Metagenomics uncovers dietary adaptations for chitin digestion in the gut microbiota of convergent myrmecophagous mammals. mSystems 2023; 8:e0038823. [PMID: 37650612 PMCID: PMC10654083 DOI: 10.1128/msystems.00388-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 06/19/2023] [Indexed: 09/01/2023] Open
Abstract
IMPORTANCE Myrmecophagous mammals are specialized in the consumption of ants and/or termites. They do not share a direct common ancestor and evolved convergently in five distinct placental orders raising questions about the underlying adaptive mechanisms involved and the relative contribution of natural selection and phylogenetic constraints. Understanding how these species digest their prey can help answer these questions. More specifically, the role of their gut microbial symbionts in the digestion of the insect chitinous exoskeleton has not been investigated in all myrmecophagous orders. We generated 29 new gut metagenomes from nine myrmecophagous species to reconstruct more than 300 bacterial genomes in which we identified chitin-degrading enzymes. Studying the distribution of these chitinolytic bacteria among hosts revealed both shared and specific bacteria between ant-eating species. Overall, our results highlight the potential role of gut symbionts in the convergent dietary adaptation of myrmecophagous mammals and the evolutionary mechanisms shaping their gut microbiota.
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Affiliation(s)
- Sophie Teullet
- Institut des Sciences de l’Evolution de Montpellier (ISEM), Univ Montpellier, CNRS, IRD, Montpellier, France
| | - Marie-Ka Tilak
- Institut des Sciences de l’Evolution de Montpellier (ISEM), Univ Montpellier, CNRS, IRD, Montpellier, France
| | - Amandine Magdeleine
- Institut des Sciences de l’Evolution de Montpellier (ISEM), Univ Montpellier, CNRS, IRD, Montpellier, France
| | - Roxane Schaub
- CIC AG/Inserm 1424, Centre Hospitalier de Cayenne Andrée Rosemon, Cayenne, French Guiana, France
- Tropical Biome and immunopathology, Université de Guyane, Labex CEBA, DFR Santé, Cayenne, French Guiana, France
| | - Nora M. Weyer
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
| | - Wendy Panaino
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- Centre for African Ecology, School of Animals, Plant, and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Andrea Fuller
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
| | - W. J. Loughry
- Department of Biology, Valdosta State University, Valdosta, Georgia, USA
| | - Nico L. Avenant
- National Museum and Centre for Environmental Management, University of the Free State, Bloemfontein, South Africa
| | - Benoit de Thoisy
- Institut Pasteur de la Guyane, Cayenne, French Guiana, France
- Kwata NGO, Cayenne, French Guiana, France
| | - Guillaume Borrel
- Evolutionary Biology of the Microbial Cell, Institut Pasteur, Université Paris Cité, Paris, France
| | - Frédéric Delsuc
- Institut des Sciences de l’Evolution de Montpellier (ISEM), Univ Montpellier, CNRS, IRD, Montpellier, France
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Ferreira-Cardoso S, Claude J, Goswami A, Delsuc F, Hautier L. Flexible conservatism in the skull modularity of convergently evolved myrmecophagous placental mammals. BMC Ecol Evol 2022; 22:87. [PMID: 35773630 PMCID: PMC9248141 DOI: 10.1186/s12862-022-02030-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 06/06/2022] [Indexed: 12/05/2022] Open
Abstract
Background The skull of placental mammals constitutes one of the best studied systems for phenotypic modularity. Several studies have found strong evidence for the conserved presence of two- and six-module architectures, while the strength of trait correlations (integration) has been associated with major developmental processes such as somatic growth, muscle-bone interactions, and tooth eruption. Among placentals, ant- and termite-eating (myrmecophagy) represents an exemplar case of dietary convergence, accompanied by the selection of several cranial morphofunctional traits such as rostrum elongation, tooth loss, and mastication loss. Despite such drastic functional modifications, the covariance patterns of the skull of convergently evolved myrmecophagous placentals are yet to be studied in order to assess the potential consequences of this dietary shift on cranial modularity. Results Here, we performed a landmark-based morphometric analysis of cranial covariance patterns in 13 species of myrmecophagous placentals. Our analyses reveal that most myrmecophagous species present skulls divided into six to seven modules (depending on the confirmatory method used), with architectures similar to those of non-myrmecophagous placentals (therian six modules). Within-module integration is also similar to what was previously described for other placentals, suggesting that most covariance-generating processes are conserved across the clade. Nevertheless, we show that extreme rostrum elongation and tooth loss in myrmecophagid anteaters have resulted in a shift in intermodule correlations in the proximal region of the rostrum. Namely, the naso-frontal and maxillo-palatine regions are strongly correlated with the oro-nasal module, suggesting an integrated rostrum conserved from pre-natal developmental processes. In contrast, the similarly toothless pangolins show a weaker correlation between the anterior rostral modules, resembling the pattern of toothed placentals. Conclusions These results reveal that despite some integration shifts related to extreme functional and morphological features of myrmecophagous skulls, cranial modular architectures have conserved the typical mammalian scheme. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-022-02030-9.
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Scheidt A, Ditzel PC, Geiger SM, Wagner FC, Mülling CKW, Nyakatura JA. A therian mammal with sprawling kinematics? Gait and 3D forelimb X-ray motion analysis in tamanduas. J Exp Biol 2022; 225:275397. [PMID: 35554550 DOI: 10.1242/jeb.243625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 05/08/2022] [Indexed: 10/18/2022]
Abstract
Therian mammals are known to move their forelimbs in a parasagittal plane, retracting the mobilised scapula during stance phase. Non-cursorial therian mammals often abduct the elbow out of the shoulder-hip parasagittal plane. This is especially prominent in Tamandua (Xenarthra), which suggests they employ aspects of sprawling (e.g., lizard-like-) locomotion. Here, we test if tamanduas use sprawling forelimb kinematics, i.e., a largely immobile scapula with pronounced lateral spine bending and long-axis rotation of the humerus. We analyse high speed videos and use X-ray motion analysis of tamanduas walking and balancing on branches of varying inclinations and provide a quantitative characterization of gaits and forelimb kinematics. Tamanduas displayed lateral sequence lateral-couplets gaits on flat ground and horizontal branches, but increased diagonality on steeper in- and declines, resulting in lateral sequence diagonal-couplets gaits. This result provides further evidence for high diagonality in arboreal species, likely maximising stability in arboreal environments. Further, the results reveal a mosaic of sprawling and parasagittal kinematic characteristics. The abducted elbow results from a constantly internally rotated scapula about its long axis and a retracted humerus. Scapula retraction contributes considerably to stride length. However, lateral rotation in the pectoral region of the spine (range: 21°) is higher than reported for other therian mammals. Instead, it is similar to skinks and alligators, indicating an aspect generally associated with sprawling locomotion is characteristic for forelimb kinematics of tamanduas. Our study contributes to a growing body of evidence of highly variable non-cursorial therian mammal locomotor kinematics.
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Affiliation(s)
- Adrian Scheidt
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt Universität zu Berlin, Philippstraße 13, 10115 Berlin, Germany
| | - Paulo C Ditzel
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt Universität zu Berlin, Philippstraße 13, 10115 Berlin, Germany
| | - Sandra M Geiger
- Institute of Veterinary Anatomy, Histology and Embryology, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany
| | - Franziska C Wagner
- Institute of Veterinary Anatomy, Histology and Embryology, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany
| | - Christoph K W Mülling
- Institute of Veterinary Anatomy, Histology and Embryology, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany
| | - John A Nyakatura
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt Universität zu Berlin, Philippstraße 13, 10115 Berlin, Germany
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Sahd L, Bennett NC, Kotzé SH. Hind foot drumming: Volumetric micro-computed tomography investigation of the hind limb musculature of three African mole-rat species (Bathyergidae). J Anat 2022; 240:23-33. [PMID: 34374084 PMCID: PMC8655198 DOI: 10.1111/joa.13534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/26/2021] [Accepted: 07/28/2021] [Indexed: 11/28/2022] Open
Abstract
Several species of African mole-rats use seismic signalling by means of hind foot drumming for communication. The present study aimed to create three-dimensional reconstructions and compare volumetric measurements of 27 muscles of the hind limb of two drumming (Georychus capensis and Bathyergus suillus) and one non-drumming (Cryptomys hottentotus natalensis) species of African mole-rats. Diffusible iodine contrast-enhanced micro-computed tomography (diceCT) scans were performed on six specimens per species. Manual segmentation of the scans using VGMAX Studio imaging software allowed for individual muscles to be separated while automatically determining the volume of each muscle. The volume of the individual muscles was expressed as a percentage of the total hind limb volume and statistically compared between species. Subsequently, three-dimensional reconstructions of these muscles were created. Musculus gracilis anticus had a significantly larger percentage of the total hind limb muscle volume in both drumming species compared to the non-drumming C. h. natalensis. Furthermore, several hip and knee extensors, namely mm. gluteus superficialis, semimembranosus, gluteofemoralis, rectus femoris and vastus lateralis, had significantly larger muscle volume percentages in the two drumming species (G. capensis and B. suillus) compared to the non-drumming species. While not statistically significant, G. capensis had larger muscle volume percentages in several key hip and knee extensors compared to B. suillus. Additionally, G capensis had the largest summed percentage of the total hind limb volume in the hip flexor, hip extensor, knee extensor and ankle plantar flexor muscle groups in all the three species. This could be indicative of whole muscle hypertrophy in these muscles due to fast eccentric contractions that occur during hind foot drumming. However, significantly larger muscle volume percentages were observed in the scratch digging B. suillus compared to the other two chisel tooth digging species. Moreover, while not statistically significant, B. suillus had larger muscle volume percentages in several hip extensor and knee flexor muscles compared to G. capensis (except for m. vastus lateralis). These differences could be due to the large relative size of this species but could also be influenced by the scratch digging strategy employed by B. suillus. Therefore, while the action of hind foot drumming seems to influence certain key muscle volumes, digging strategy and body size may also play a role.
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Affiliation(s)
- Lauren Sahd
- Division of Clinical AnatomyDepartment of Biomedical SciencesFaculty of Medicine and Health SciencesStellenbosch UniversityCape TownSouth Africa
| | - Nigel C. Bennett
- Department of Zoology and EntomologyMammal Research InstituteUniversity of PretoriaPretoriaSouth Africa
| | - Sanet H. Kotzé
- Division of Clinical AnatomyDepartment of Biomedical SciencesFaculty of Medicine and Health SciencesStellenbosch UniversityCape TownSouth Africa
- Department of Biomedical SciencesRoss University School of Veterinary MedicineBasseterreSt Kitts and Nevis
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