Macroscopic description of the external and middle ear of paca (Cuniculus paca Linnaeus, 1766)

Abstract

RESUMO.-[Descrição macroscópica da orelha externa e media da paca (Cuniculus paca Linnaeus, 1766).] A paca (Cuniculus paca), um dos maiores roedores da fauna brasileira, possui características inerentes à sua espécie que podem contribuir como uma nova opção de animal experimental; assim, considerando-se que há crescente busca por modelos experimentais apropriados para pesquisas audiológicas e otológica cirúrgicas foram analisados e descritos em detalhes a anatomia macroscópica e ultraestrutural da orelha desse roedor. Para o estudo, utilizaram-se 15 animais adultos provenientes do plantel do Setor de Animais Silvestres da Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, Jaboticabal/SP. Após anestesia e eutanásia, avaliou-se toda a composição da orelha externa, registrando-se e descrevendo-se os detalhes, também se dissecou a região temporal para melhor visibilização e detalhamento da bula timpânica e estas foram removidas e abertas a fim de expor as estruturas da orelha, as quais foram analisadas, macroscopicamente e ultraestruturalmente. O pavilhão auricular apresenta forma triangular e côn-cava com cristas irregulares e ápice pontiagudo; o conduto auditivo externo é sinuoso em seu trajeto até a membrana timpânica; a bula timpânica encontra-se na parte poste- , one of the largest rodents of the Brazilian fauna, has inherent characteristics of its species which can conribute as a new option for animal experimantation. As there is a growing demand for suitable experimental models in audiologic and otologic surgical research, the gross anatomy and ultrastructural ear of this rodent have been analyzed and described in detail. Fifteen adult pacas from the Wild Animals Sector herd of Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, were used in this study. After anesthesia and euthanasia, we evaluated the entire composition of the external ear, registering and ddescribing the details; the temporal region was often dissected for a better view and detailing of the tympanic bulla which was removed and opened to expose the ear structures analyzed mascroscopically and ultrastructurally. The ear pinna has a triangular and concave shape with irregular ridges and sharp apex. The external auditory canal is winding in its path to the tympanic mebrane. The tympanic bulla is is on the back-bottom of the skull. The middle ear is formed by a cavity region filled with bone and membranous structures bounded by the tympanic membrane and the oval and round windows. The tympanic membrane is flat and seals the ear canal. The anatomy of the paca ear is similar to the guinea pig and from the viewpoint of experimental model has major advantages compared with the mouse ear.INDEX TERMS: Ear, paca, Cuniculus paca, rodent, temporal bone, ultrastructure. rior-inferior do crânio; a orelha média é formada por uma região cavitária preenchida por estruturas ósseas e membranosas. É delimitada pela membrana timpânica e as janelas redonda e oval, sendo a membrana timpânica de forma plana e que veda todo o conduto audi...

Morphological and morphometrical study of the auditory ossicles in chinchilla

“…The stapes, the smallest of three bones, has an overall pyramidal shape (similarly with many species studied; Berghes et al, ; Gürbüz et al, ; Martins et al, ). It consists of a defined head (with the corresponding articular surface), less evident neck, two crura and the base.…”

“…Same joint articular complex is described, except for chinchilla , in guinea pig, degu (Argyle & Mason, ; Şanlı et al, ), and naked mole rat (Mason, Cornwall, & Smith, ). In other species, literature data mention two easily separable bones (rat; Argyle & Mason, ; Martins et al, ). More than this, in case of minipig (HaiJin et al, ), a synovial joint is described in case of the maleo‐incal joint, contrary to the one in humans (Isaacson, ) that remains a cartilaginous one throughout the entire life.…”

“…Data related to the detailed anatomy of the auditory ossicles are relatively limited. A few elements were reported in case of birds (Mills, ), different rodents (Kerber & Sánchez‐Villagra, ; Kurtul et al, ; Lee, Park, Kang, & Choung, ; Li, Gao, Ding, & Salvi, ; Maier, Tröscher, & Ruf, ; Martins et al, ; Mohammadpour, , ; Şanlı, Sedat, & Oztürk, ), humans (García‐Real, Kass, Sturges, & Wisner, ; Isaacson, ), swine (Gurr, Kevenhörster, Stark, Pearson, & Dazert, ; Hoffstetter et al, ; Pracy, White, Mustafa, Smith, & Perry, ), miniature pigs (HaiJin et al, ), sheep (Ayres Seibel, Lavinsky, & Preto De Oliveira, ; Simaei, Soltanalinejad, Najafi, & Shalizar Jalali, ), chinchilla (Vrettakos, Dear, & Saunders, ; Wang & Gan, ), cat (Beck, Kilchling, & Meyer‐Lindenberg, ; Seifert et al, ), dog (Berghes, Parvu, Cucoanes, & Cuca, ) and wolf (Gürbüz et al, ), badger (Rozen‐Rechels, Peigné, Germain, & Ladevèze, ), horse (Blanke, Aupperle, Seeger, Kubick, & Schusser, ), donkey (Awal et al, ), common degu (32) or other subterranean cavimorphes (Argyle & Mason, ).…”

Morphological and morphometrical aspects of the auditory ossicles in goat (Capra hircus)

“…The three ossicles were presented as individualized pieces, unlike the situation described in chinchilla (Carrasco et al, 2008; Martonos et al., 2019; Wang & Gan, 2016), guinea pig (Amin & Tucker, 2006; Guan et al., 2019), common degu (Argyle & Mason, 2008), spotted paca (Martins et al., 2015) or the naked mole‐rat (Argyle & Mason, 2008) where a fused assembly—the malleal–incudo complex—is described as the result of the fusion of malleus and incus. Such a fusion is described in the case of humans and mice as pathological, being associated with loss of hearing, as malleus and incus develop embryologically from a single condensation that splits to form the two ossicles (Amin & Tucker, 2006).…”

Anatomical, Histological, and Morphometrical Investigations of the Auditory Ossicles in Chlorocebus aethiops sabaeus from Saint Kitts Island

“…Specifically, the long crus of this ossicle may be affected in cases of chronic otitis in the middle ears [ 36 , 46 , 47 , 48 ]. Another important fact associated with the morphology of this ossicle refers to the existence, in some particular instances, of the malleo-incal complex, which is the result of the fusion of the first two ossicles, noted in Heterocephalus glaber [ 49 , 50 ], Cuniculus paca [ 51 ], Octodon degus [ 52 ], guinea pigs [ 53 , 54 ], and chinchillas [ 32 , 54 , 55 , 56 ]. The malleo-incal complex is also implicated in specific cases of humans and mice as a probable explanation for deafness [ 53 ].…”