Macroscopic and histological aspects of the pharynx and larynx of the giant anteater (Myrmecophaga tridactylaLinnaeus, 1758)

Abstract

Giant anteater (Myrmecophaga tridactyla) is an endangered species that resides in much of Latin America, but it has been losing its habitat, especially in the Cerrado biome, where it constantly suffers traumas resulting from fires and roadkill. The anatomical knowledge of structures of the respiratory system is important for a better morphophysiological understanding of the species. Thus, this study aimed to perform the macroscopic and histomorphological description of the pharynx and larynx of the giant anteater. Twelve adult giant anteaters were used, three of them fixed in buffered formalin for further dissection and pharynx and larynx macroscopic analysis of structures. From the other animals, samples of the pharynx and larynx were collected and prepared for histological evaluation under optical microscope. Macroscopically, their pharynx and soft palate are extensive, and the anatomical location of these structures and the larynx differs greatly from that described in other species. The larynx, although more caudal, was similar to that of other animals. Histologically, the epithelium of these regions varied between the pseudostratified ciliated columnar and the non‐keratinized stratified squamous epithelium. Laryngeal cartilages were composed of elastic (epiglotti) and hyaline cartilages (arytenoid, cricoid and thyroid cartilage), with an ossification process and glandular clusters around the hyaline cartilage. The distinct anatomical location of the pharynx and larynx of Myrmecophaga tridactyla is the main macroscopic finding of this study, besides the length of the pharynx and soft palate of these animals.

Morphology and computed tomography of the larynx in the white‐eared opossum (Didelphis albiventris)

“…cartilage. The same gross anatomy has been described for crab-eating fox (Souza Junior et al, 2016), nine-banded armadillo (Fonseca et al, 2017) and giant anteater (Oliveira et al, 2023). The thyroid and cricoid cartilages were fused ventromedially and this anatomical feature has been previously reported in marsupials such as koala (Frey et al, 2018).…”

“…The larynx in the white-eared opossum is formed by four distinc cartilages (epiglottis, and thyroid, cricoid and arytenoids cartilages), similar to those observed in other wild mammals such as crab-eating fox (Souza Junior et al, 2016), nine-banded armadillo (Fonseca et al, 2017), paca (Ruaro et al, 2021) and giant anteater (Oliveira et al, 2023). However, cuneiform and corniculate cartilages cited in the agouti (Silva et al, 2014) were not observed in the white-eared opossum.…”

“…The same topography was related to the crab-eating fox (Souza Junior et al, 2016). On the other hand, the larynx is located a position at the level of the sixth (C6) and seventh (C7) cervical vertebrae in the giant anteater (Oliveira et al, 2023). The knowledge of the larynx topography is important because for the knowledge of the anatomical characteristics of the species and for clinical and surgical procedures, such as endotracheal intubation.…”

“…Thyroid, cricoid, and arytenoid cartilages are formed by hyaline cartilage, with typical arrangement consisting of chondrocytes and extracellular matrix surrounded by perichondrium, as reported in coatis (Oliveira et al, 2012), capybaras (Moreto et al, 2017), nine-banded armadillo (Fonseca et al, 2017), and giant anteater (Oliveira et al, 2023). The hyaline cartilage provides the necessary rigidity for muscle fixation that promotes movement between these cartilages (Ruaro et al, 2021).…”

“…In general, the morphology of the laryngeal cartilaginous framework in the white-eared opossum was similar to those reported to other mammals. Oliveira et al (2023) claimed that divergences about larynx morphology could be frequent and are related to the lifestyle and eating habits of the species. The morphology of the white-eared opossum epiglottis resembles a 'leaf' formed by elastic cartilage.…”