Comparative anatomy of the bony labyrinth of extant and extinct porpoises (Cetacea: Phocoenidae)

Racicot, Rachel A.; Gearty, William; Kohno, Naoki; Flynn, John J.

doi:10.1111/bij.12857

Cited by 21 publications

(43 citation statements)

References 54 publications

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“…Distributions of 90var measurements taken two different ways – the ‘direct’ method (of Racicot et al. ), and the ‘plane’ method ( cf . Malinzak et al.…”

Section: Resultsmentioning

confidence: 99%

“…; Racicot & Colbert, ; Ekdale & Racicot, ; Racicot et al. ; Mourlam & Orliac, ). Original CT data and 3D *.stl files of the endocasts will be made available through morphosource.org, those scanned at UTCT are available by request from UTCT and digimorph.org staff.…”

Section: Methodsmentioning

confidence: 98%

“…; Racicot & Colbert, ; Racicot et al. ). The 3D magic wand tool at varying thresholds and other region of interest (ROI) tools were used.…”

Section: Methodsmentioning

confidence: 99%

“…a,c and Table ), following Racicot et al. () and on planes manually inserted through the canals with the ‘Oblique Slice’ module in avizo (‘plane method’, Supporting Information Fig. b,c and Table ).…”

Section: Methodsmentioning

confidence: 99%

“…, ) have resulted in its exclusion from analyses until fairly recently (Ekdale & Racicot, ; Racicot et al. ). A method that has recently been employed for calculating rotational sensitivity as associated with locomotor behavior of mammals, 90var (Malinzak et al.…”

Section: Introductionmentioning

confidence: 99%

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Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae)

2018

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Narwhals (Monodon monoceros) and belugas (Delphinapterus leucas) are the only extant members of the Monodontidae, and are charismatic Arctic-endemic cetaceans that are at risk from global change. Investigating the anatomy and sensory apparatuses of these animals is essential to understanding their ecology and evolution, and informs efforts for their conservation. Here, we use X-ray CT scans to compare aspects of the endocranial and inner ear labyrinth anatomy of extant monodontids and use the overall morphology to draw larger inferences about the relationship between morphology and ecology. We show that differences in the shape of the brain, vasculature, and neural canals of both species may relate to differences in diving and other behaviors. The cochleae are similar in morphology in the two species, signifying similar hearing ranges and a close evolutionary relationship. Lastly, we compare two different methods for calculating 90var - a calculation independent of body size that is increasingly being used as a proxy for habitat preference. We show that a 'direct' angular measurement method shows significant differences between Arctic and other habitat preferences, but angle measurements based on planes through the semicircular canals do not, emphasizing the need for more detailed study and standardization of this measurement. This work represents the first comparative internal anatomical study of the endocranium and inner ear labyrinths of this small clade of toothed whales.

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“…Distributions of 90var measurements taken two different ways – the ‘direct’ method (of Racicot et al. ), and the ‘plane’ method ( cf . Malinzak et al.…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 98%

“…; Racicot & Colbert, ; Racicot et al. ). The 3D magic wand tool at varying thresholds and other region of interest (ROI) tools were used.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae)

2018

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The so‐called foramen singulare in cetacean periotics is actually the superior vestibular area

Ichishima

Kawabe

Sawamura

2021

The Anatomical Record

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It is nearly 100 years ago that the “foramen singulare” was first identified in cetacean periotics. Since then, the “foramen singulare” has been recognized in periotics of many cetacean species, extant or extinct. Surprisingly, however, it has never been confirmed if the foramen singulare in cetacean periotics is really homologous to that in other mammals. It is known that in mammals including humans the posterior ampullary nerve, which innervates the posterior semicircular duct, passes through the foramen singulare. We use an X‐ray micro‐CT scan to examine endocasts of the bony labyrinth of the inner ear of cetacean periotics, showing that the osseous canal extending from the so‐called foramen singulare goes toward the anterior bony ampulla, meaning that the alleged foramen singulare in cetacean periotics is really the superior vestibular area, through which the utriculoampullary nerve enters. The transverse crest is quite significant to identify each quadrant of the fundus of the internal acoustic meatus, but in many cetacean species the transverse crest is poorly developed, almost imperceptible in some species, and this could have brought confusion into the interpretation over the superior vestibular area and the foramen singulare. The bony septum separating the cerebral aperture of the facial canal from the foramen singulare is not the transverse crest, but the perpendicular crest. The foramen singulare is not a distinct foramen separated from the inferior vestibular area. Instead, the true foramen singulare opens near the inferior vestibular area in the internal acoustic meatus in cetacean periotics.

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Cochlear apical morphology in toothed whales: Using the pairing hair cell—Deiters' cell as a marker to detect lesions

IJsseldijk

Piscitelli-Doshkov

Ostertag

et al. 2021

The Anatomical Record

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The apex or apical region of the cochlear spiral within the inner ear encodes for low‐frequency sounds. The disposition of sensory hair cells on the organ of Corti is largely variable in the apical region of mammals, and it does not necessarily follow the typical three‐row pattern of outer hair cells (OHCs). As most underwater noise sources contain low‐frequency components, we expect to find most lesions in the apical region of the cochlea of toothed whales, in cases of permanent noise‐induced hearing loss. To further understand how man‐made noise might affect cetacean hearing, there is a need to describe normal morphological features of the apex and document interspecific anatomic variations in cetaceans. However, distinguishing between apical normal variability and hair cell death is challenging. We describe anatomical features of the organ of Corti of the apex in 23 ears from five species of toothed whales (harbor porpoise Phocoena phocoena, spinner dolphin Stenella longirostris, pantropical spotted dolphin Stenella attenuata, pygmy sperm whale Kogia breviceps, and beluga whale Delphinapterus leucas) by scanning electron microscopy and immunofluorescence. Our results showed an initial region where the lowest frequencies are encoded with two or three rows of OHCs, followed by the typical configuration of three OHC rows and three rows of supporting Deiters' cells. Whenever two rows of OHCs were detected, there were usually only two corresponding rows of supporting Deiters' cells, suggesting that the number of rows of Deiters' cells is a good indicator to distinguish between normal and pathological features.

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Comparative anatomy of the bony labyrinth of extant and extinct porpoises (Cetacea: Phocoenidae)

Cited by 21 publications

References 54 publications

Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae)

Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae)

The so‐called foramen singulare in cetacean periotics is actually the superior vestibular area

Cochlear apical morphology in toothed whales: Using the pairing hair cell—Deiters' cell as a marker to detect lesions

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