Anatomic and histologic analysis of paca larynx (Cuniculus paca, Linnaeus 1766)

Abstract

Paca (Cuniculus paca) has encouraged research as an experimental model both in the human medicine and veterinary, as well as the economic exploitation of its meat cuts, which favored its zootechnical use. There are no anatomical, microscopic descriptions and measurements of the larynx in this rodent. Eight pacas were dissected from the wild animal’s sector of the Faculty of Agricultural and Veterinary Sciences of the University of the State of São Paulo. The larynx was observed located in the ventral region of the neck, ventral to the esophagus, connecting the pharynx to the trachea, with cylindrical and irregular shape. Laryngeal cartilages (epiglottic, thyroid, cricoid and arytenoid) are interconnected and have different shapes. Thyroid showed greater length and width, compared to the others. Laryngeal cartilages were submitted to histological processing and stained with hematoxylin-eosin and Masson's trichrome. The epiglottic cartilage was stained with toluidine blue. Laryngeal cartilages thyroid, cricoid and the lower portion of the arytenoids are of hyaline origin and, in contrast, the epiglottis and the upper portion of the arytenoids are elastic. This latter cartilage demonstrated taste buds. The results will be able to auxiliate in veterinary care and as well as the conservation programs for this rodent.

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

“…The thyroid cartilage was the largest cartilage observed in this study. The gross anatomy of the thyroid cartilage in the white‐eared opossum is similar to those described for other mammals such as European red deer (Frey & Riede, 2013), agouti (Silva et al., 2014), crab‐eating fox (Souza Junior et al., 2016), nine‐banded armadillo (Fonseca et al., 2017), capybara (Moreto et al., 2017), koala (Frey et al., 2018), impala (Frey et al., 2020), paca (Ruaro et al., 2021) and giant anteater (Oliveira et al., 2023). Concerning the rostral and caudal cornus of the thyroid cartilage, there is a similarity with those reported, where the rostral and caudal cornus articulate with the thyrohyoid bone (hyoid apparatus) and with the lateral portion of the cricoid cartilage, respectively.…”

“…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.…”

“…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).…”

“…The morphology of the mammal larynx has been described in several species, such as rat (Smith, 1977), coatis (Oliveira et al., 2012), agouti (Silva et al., 2014), crab‐eating fox (Souza Junior et al., 2016) and paca (Ruaro et al., 2021). Although there is a study on the opossum larynx (Bertassoli et al., 2013), there is no description of larynx using radiography or computed tomography (CT) in the white‐eared opossum as far as our our knowledge.…”