Morphometry of the vestibular organ in neonate and adult African mole-rats Cryptomys species

Although increasingly popular as a laboratory species, very little is known about the peripheral auditory system of the naked mole-rat, Heterocephalus glaber. In this study, middle and inner ears of naked mole-rats of a range of ages were examined using micro-computed tomography and dissection. The ears of five other bathyergid species (Bathyergus suillus, Cryptomys hottentotus, Fukomys micklemi, Georychus capensis and Heliophobius argenteocinereus) were examined for comparative purposes. The middle ears of bathyergids show features commonly found in other members of the Ctenohystrica rodent clade, including a fused malleus and incus, a synovial stapedio-vestibular articulation and the loss of the stapedius muscle. Heterocephalus deviates morphologically from the other bathyergids examined in that it has a more complex mastoid cavity structure, poorly-ossified processes of the malleus and incus, a ‘columelliform’ stapes and fewer cochlear turns. Bathyergids have semicircular canals with unusually wide diameters relative to their radii of curvature. How the lateral semicircular canal reaches the vestibule differs between species. Heterocephalus has much more limited high-frequency hearing than would be predicted from its small ear structures. The spongy bone forming its ossicular processes, the weak incudo-stapedial articulation, the columelliform stapes and (compared to other bathyergids) reduced cochlear coiling are all potentially degenerate features which might reflect a lack of selective pressure on its peripheral auditory system. Substantial intraspecific differences were found in certain middle and inner ear structures, which might also result from relaxed selective pressures. However, such interpretations must be treated with caution in the absence of experimental evidence.

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“…[65–67]). The membranous semicircular canals of Fukomys mole-rats have also been found not to expand postnatally [31]. …”

Section: Discussionmentioning

confidence: 99%

Ear Structures of the Naked Mole-Rat, Heterocephalus glaber, and Its Relatives (Rodentia: Bathyergidae)

2016

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“…The mole-rats of the genus Cryptomys grow only very slowly and display a remarkable polymorphism in body size which is associated with age, social status, and sex. Even the body mass of a n adult individual can fluctuate remarkably in the course of its life (Burda, 1990; unpublished observations) However, within one species, the size of the vestibular organ was not correlated with body size (Lindenlaub and Burda, 1993;present paper). Consequently, we may assume that the size (including its variability) of the vestibular organ is primarily species-specific.…”

Section: Discussionmentioning

confidence: 95%

“…The specimens remained immersed under water during the whole preparation and the photographic documentation (cf. Curthoys and Oman, 1986;Lindenlaub and Burda, 1993). Contralateral vestibular organs were embedded in paraffin and serially sectioned using standard histological methods.…”

Section: Methodsmentioning

confidence: 99%

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Functional allometry of the semicircular ducts in subterranean mole‐rats Cryptomys (Bathyergidae, rodentia)

Lindenlaub

Burda

1994

Anat. Rec.

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“…After perfusion, the periotic bones were dissected, the perilymphatic spaces opened and the specimens stored in the fixative. The semicircular ducts were exposed by means of the microdissection technique described in detail by Engström et al (1966), Curthoys and Oman (1986), and Lindenlaub and Burda (1993). The dissection was carried out underwater using a WILD stereomicroscope with a magnification up to 50×.…”

Section: Methodsmentioning

confidence: 99%

Morphological, morphometric, and functional differences in the vestibular organ of different breeds of the rat (Rattus norvegicus)

Lindenlaub

Oelschläger

1999

Anat. Rec.

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In the laboratory rat, differences in shape, dimension and function of the cochlea have been reported for various breeds. In contrast, no comparable investigations to date have been undertaken for the vestibular organ in different breeds of the rat. Vestibular organs of two breeds of rat (Wistar, Sprague-Dawley) were analyzed morphologically and morphometrically by means of microdissection techniques in order to determine the mechanical sensitivity of the cupula according to Oman et al; (Acta Otolaryngol., 1987;103:1-13, 1987). Differences in shape of the lateral semicircular duct exist between the two breeds and the cupular mechanical sensitivity is significantly higher in Wistar than in Sprague-Dawley rats. With respect to the other semicircular ducts, no differences in shape were found between the two strains. The cupular mechanical sensitivity of the anterior semicircular duct, however, is higher in Wistar than in Sprague-Dawley rats. The breeds also differ in the shape of their utriculus; obviously a correlation exists between the latter and the cupular mechanical sensitivity of the semicircular ducts. There are differences in the vestibular organs between the two breeds of the laboratory rat investigated. The cupular mechanical sensitivity of the semicircular duct does not seem to be correlated to body mass. The size and morphology of the utriculus influence the mechanical sensitivity of a single duct, but differences only become significant if other parameters also differ.

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Morphometry of the vestibular organ in neonate and adult African mole-rats Cryptomys species

Cited by 7 publications

References 9 publications

Ear Structures of the Naked Mole-Rat, Heterocephalus glaber, and Its Relatives (Rodentia: Bathyergidae)

Ear Structures of the Naked Mole-Rat, Heterocephalus glaber, and Its Relatives (Rodentia: Bathyergidae)

Functional allometry of the semicircular ducts in subterranean mole‐rats Cryptomys (Bathyergidae, rodentia)

Morphological, morphometric, and functional differences in the vestibular organ of different breeds of the rat (Rattus norvegicus)

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