Inner ear development in cetaceans

Thean, Tara; Kardjilov, Nikolay; Asher, Robert J.

doi:10.1111/joa.12548

Cited by 18 publications

(21 citation statements)

References 56 publications

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“…The shape of the inner ear of baleen whales in both its vestibular and cochlear parts is partly explained by their phylogenetic relationships 15 . Early development of the inner ear largely before birth may partly explain its strong link to phylogeny 16 – 18 . In addition, intraspecific variability of this structure is lower than the inter-genera disparity giving solid grounds to its use in systematics and phylogeny 19 – 21 .…”

Section: Introductionmentioning

confidence: 99%

The bony labyrinth of toothed whales reflects both phylogeny and habitat preferences

Costeur¹,

Grohé²,

Aguirre-Fernández³

et al. 2018

Sci Rep

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The inner ear of toothed whales (odontocetes) is known to have evolved particular shapes related to their abilities to echolocate and move under water. While the origin of these capacities is now more and more examined, thanks to new imaging techniques, little is still known about how informative inner ear shape could be to tackle phylogenetic issues or questions pertaining to the habitat preferences of extinct species. Here we show that the shape of the bony labyrinth of toothed whales provides key information both about phylogeny and habitat preferences (freshwater versus coastal and fully marine habitats). Our investigation of more than 20 species of extinct and modern odontocetes shows that the semi-circular canals are not very informative, in contrast to baleen whales, while the cochlea alone bears a strong signal. Inner ear shape thus provides a novel source of information to distinguish between morphologically convergent lineages (e.g. river dolphins).

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Section: Introductionmentioning

confidence: 99%

The bony labyrinth of toothed whales reflects both phylogeny and habitat preferences

Costeur¹,

Grohé²,

Aguirre-Fernández³

et al. 2018

Sci Rep

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“…The cetacean auditory system has undergone dramatic modifications associated with at least three major shifts throughout cetacean evolutionary history: (1) the land-to-sea transition; (2) ultrasonic hearing for echolocation; and (3) infrasonic hearing in mysticetes ( Ritsche et al 2018 ; Thean, Kardjilov & Asher, 2017 ; Thewissen & Williams, 2002 ; Spoor & Thewissen, 2008 ; Thewissen et al, 2001 ; Fleischer, 1976 ; Schevill & McBride, 1953 ). Throughout these changes, cetaceans have maintained a unique auditory structure: the pachyosteoslerotic tympanic bulla.…”

Section: Introductionmentioning

confidence: 99%

What are the limits on whale ear bone size? Non-isometric scaling of the cetacean bulla

Groves

Peredo

Pyenson

2021

PeerJ

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The history of cetaceans demonstrates dramatic macroevolutionary changes that have aided their transformation from terrestrial to obligate aquatic mammals. Their fossil record shows extensive anatomical modifications that facilitate life in a marine environment. To better understand the constraints on this transition, we examined the physical dimensions of the bony auditory complex, in relation to body size, for both living and extinct cetaceans. We compared the dimensions of the tympanic bulla, a conch-shaped ear bone unique to cetaceans, with bizygomatic width—a proxy for cetacean body size. Our results demonstrate that cetacean ears scale non-isometrically with body size, with about 70% of variation explained by increases in bizygomatic width. Our results, which encompass the breadth of the whale fossil record, size diversity, and taxonomic distribution, suggest that functional auditory capacity is constrained by congruent factors related to cranial morphology, as opposed to allometrically scaling with body size.

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“…Despite increased interest in the morphological development and ontogeny of mammals [ 22 , 23 , 38 , 47 , 66 , 67 ], many questions regarding the ontogenetic basis of modern phenotypic diversity remain unanswered. Bats are an excellent example of ecomorphological diversity within Mammalia, having a wide range of dietary specialisations [ 68 ], and exhibiting a range of locomotor strategies [ 69 ].…”

Section: Introductionmentioning

confidence: 99%

Postcranial heterochrony, modularity, integration and disparity in the prenatal ossification in bats (Chiroptera)

et al. 2019

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BackgroundSelf-powered flight is one of the most energy-intensive types of locomotion found in vertebrates. It is also associated with a range of extreme morpho-physiological adaptations that evolved independently in three different vertebrate groups. Considering that development acts as a bridge between the genotype and phenotype on which selection acts, studying the ossification of the postcranium can potentially illuminate our understanding of bat flight evolution. However, the ontogenetic basis of vertebrate flight remains largely understudied. Advances in quantitative analysis of sequence heterochrony and morphogenetic growth have created novel approaches to study the developmental basis of diversification and the evolvability of skeletal morphogenesis.Assessing the presence of ontogenetic disparity, integration and modularity from an evolutionary approach allows assessing whether flight may have resulted in evolutionary differences in the magnitude and mode of development in bats.ResultsWe quantitatively compared the prenatal ossification of the postcranium (24 bones) between bats (14 species), non-volant mammals (11 species) and birds (14 species), combining for the first time prenatal sequence heterochrony and developmental growth data. Sequence heterochrony was found across groups, showing that bat postcranial development shares patterns found in other flying vertebrates but also those in non-volant mammals. In bats, modularity was found as an axial-appendicular partition, resembling a mammalian pattern of developmental modularity and suggesting flight did not repattern prenatal postcranial covariance in bats.ConclusionsCombining prenatal data from 14 bat species, this study represents the most comprehensive quantitative analysis of chiropteran ossification to date. Heterochrony between the wing and leg in bats could reflect functional needs of the newborn, rather than ecological aspects of the adult. Bats share similarities with birds in the development of structures involved in flight (i.e. handwing and sternum), suggesting that flight altriciality and early ossification of pedal phalanges and sternum are common across flying vertebrates. These results indicate that the developmental modularity found in bats facilitates intramodular phenotypic diversification of the skeleton. Integration and disparity increased across developmental time in bats. We also found a delay in the ossification of highly adaptable and evolvable regions (e.g. handwing and sternum) that are directly associated with flight performance.Electronic supplementary materialThe online version of this article (10.1186/s12862-019-1396-1) contains supplementary material, which is available to authorized users.

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Inner ear development in cetaceans

Cited by 18 publications

References 56 publications

The bony labyrinth of toothed whales reflects both phylogeny and habitat preferences

The bony labyrinth of toothed whales reflects both phylogeny and habitat preferences

What are the limits on whale ear bone size? Non-isometric scaling of the cetacean bulla

Postcranial heterochrony, modularity, integration and disparity in the prenatal ossification in bats (Chiroptera)

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