Ear morphology and morphometry as potential forensic tools for identification of the Hausa, Igbo and Yoruba populations of Nigeria

Background The human external ear is unique in every individual in terms of shape, size and dimension making it suitable in forensic anthropology for sex estimation and personal identification purposes. The study aimed to evaluate sexual dimorphism and ethnic specificity of the external ear in major Nigerian ethnic populations. Results There was variation in the morphological features of the external ear of the sampled subjects. The external ear features vary in the right and left ears in both sexes of the ethnic groups. All variables were statistically significant (p < 0.05) except ear width. Univariate discriminant function gave sex prediction accuracies between 56.4 and 57.3% for left and right ears, respectively. Population-specific sex prediction accuracy using stepwise discriminant analysis of left ear variables ranged 58–69.7% and 57.5–74.2% for right ear. Conclusion The ear parameters showed potential for sex estimation, but cannot be solely relied upon for personal identification.

The natural adaptation and human selection history of African sheep genomes

African sheep manifest diverse but distinct physio-anatomical traits which are the outcomes of natural- and human-driven selection. Here, we generated 34.8 million variants from 150 indigenous African sheep genomes sequenced at an average depth of ∼54x for 130 samples (Ethiopia, Libya) and ∼10x for 20 samples (Sudan), representing sheep from diverse environments, tail morphology and post-Neolithic introductions to Africa. Phylogenetic and model-based admixture analysis provided evidence of four genetic groups that correspond to altitudinal geographic origins and tail morphotypes. Comparative genomic analysis identified targets of selection spanning conserved haplotype structures overlapping genes and gene families relating to hypoxia responses, caudal vertebrae and tail skeleton length, ear morphology, and tail fat-depot structure. Our findings provide novel insights underpinning variation and response to human selection and environmental adaptation, and possible pleiotropic gene interactions in indigenous African sheep genomes, which guaranteed the successful establishment of the species on the continent.

Keeping an ear out: size relationship of the tympanic bullae and pinnae in bandicoots and bilbies (marsupialia: Peramelemorphia)

Bandicoots and bilbies (Order Peramelemorphia) occupy a broad range of habitats across Australia and New Guinea, from open, arid deserts to dense forests. This once diverse group has been particularly vulnerable to habitat loss and introduced eutherian predators, and numerous species extinctions and range retractions have occurred. Understanding reasons for this loss requires greater understanding of their biology. Morphology of the pinnae and tympanic bullae varies markedly amongst species. As hearing is important for both predator avoidance and prey location, the variability in ear morphology could reflect specialisation and adaptation to specific environments, and therefore be of conservation relevance. We measured 798 museum specimens representing 29 species of Peramelemorphia. Controlling for phylogenetic relatedness and head length, pinna surface area was weakly negatively correlated with average precipitation (rainfall being our surrogate measure of vegetation productivity/complexity), and there were no environmental correlates with effective diameter (pinna width). Controlling for phylogenetic relatedness and skull length, tympanic bulla volume was negatively correlated with precipitation. Species that inhabited drier habitats, which would be open and allow sound to carry further with less obstruction, had relatively larger pinnae and tympanic bullae. By contrast, species from higher rainfall habitats, where sounds would be attenuated and diffused by dense vegetation, had the smallest pinnae and bullae, suggesting that low-frequency hearing is not as important in these habitats. Associations with temperature did not reach statistical significance. These findings highlight linkages between hearing traits and habitat that can inform conservation and management strategies for threatened species.

Hearing from the ocean and into the river: the evolution of the inner ear of Platanistoidea (Cetacea: Odontoceti)

The inner ear of the two higher clades of modern cetaceans (Neoceti) is highly adapted for hearing infrasonic (mysticetes) or ultrasonic (odontocetes) frequencies. Within odontocetes, Platanistoidea comprises a single extant riverine representative, Platanista gangetica, and a diversity of mainly extinct marine species from the late Oligocene onward. Recent studies drawing on features including the disparate tympanoperiotic have not yet provided a consensus phylogenetic hypothesis for platanistoids. Further, cochlear morphology and evolutionary patterns have never been reported. Here, we describe for the first time the inner ear morphology of late Oligocene–early Miocene extinct marine platanistoids and their evolutionary patterns. We initially hypothesized that extinct marine platanistoids lacked a specialized inner ear like P. gangetica and thus, their morphology and inferred hearing abilities were more similar to those of pelagic odontocetes. Our results reveal there is no “typical” platanistoid cochlear type, as the group displays a disparate range of cochlear anatomies, but all are consistent with high-frequency hearing. Stem odontocete Prosqualodon australis and platanistoid Otekaikea huata present a tympanal recess in their cochlea, of yet uncertain function in the hearing mechanism in cetaceans. The more basal morphology of Aondelphis talen indicates it had lower high-frequency hearing than other platanistoids. Finally, Platanista has the most derived cochlear morphology, adding to evidence that it is an outlier within the group and consistent with a >9-Myr-long separation from its sister genus Zarhachis. The evolution of a singular sound production morphology within Platanistidae may have facilitated the survival of Platanista to the present day.

Toward the Pathogenicity of the SLC26A4 p.C565Y Variant Using a Genetically Driven Mouse Model

Recessive variants of the SLC26A4 gene are globally a common cause of hearing impairment. In the past, cell lines and transgenic mice were widely used to investigate the pathogenicity associated with SLC26A4 variants. However, discrepancies in pathogenicity between humans and cell lines or transgenic mice were documented for some SLC26A4 variants. For instance, the p.C565Y variant, which was reported to be pathogenic in humans, did not exhibit functional pathogenic consequences in cell lines. To address the pathogenicity of p.C565Y, we used a genotype-based approach in which we generated knock-in mice that were heterozygous (Slc26a4+/C565Y), homozygous (Slc26a4C565Y/C565Y), and compound heterozygous (Slc26a4919-2A>G/C565Y) for this variant. Subsequent phenotypic characterization revealed that mice with these genotypes demonstrated normal auditory and vestibular functions, and normal inner-ear morphology and pendrin expression. These findings indicate that the p.C565Y variant is nonpathogenic for mice, and that a single p.C565Y allele is sufficient to maintain normal inner-ear physiology in mice. Our results highlight the differences in pathogenicity associated with certain SLC26A4 variants between transgenic mice and humans, which should be considered when interpreting the results of animal studies for SLC26A4-related deafness.

MRI features in foetal microtia

Background: Atresia of the external auditory canal is positively correlated with the difficulty and success rate of operation after birth. At present, ultrasound screening often obtains images of body position, placenta and amniotic fluid, and the detection rate is low. Moreover, it is unable to evaluate whether the external auditory canal shows atresia. Methods: We retrospectively conducted MRI features of 9 cases those were diagnosed foetal microtia from May. 2019 to Oct. 2020. Results: Nine cases of microtia foetus were analysed: male, five cases; female, four cases; right ear, five cases; left ear, four cases; and degree I, one case (bilateral external auditory canal is shown); degree II, eight cases (affected external auditory canal is not shown, six cases of normal external auditory canal shown, two cases of normal external auditory canal not shown). All parturients underwent amniocentesis full exon gene detection, of which the results were negative. The magnetic resonance imaging (MRI) features of microtia, included abnormal external ear morphology, disappearance of normal structure, mass-like and small piece-like soft tissue shadow and equal signal on T2-weighted (T2W) imaging. The upper and lower diameters were significantly smaller than that of the normal side. The MRI features of external auditory canal atresia included disappearance of T2W linear high signal shadow in the temporal bone scale. Conclusions: Foetal MRI can diagnose microtia and evaluate atresia of the external auditory canal.

Deletion of Kcnj16 in Mice Does Not Alter Auditory Function

Endolymphatic potential (EP) is the main driving force behind the sensory transduction of hearing, and K+ is the main charge carrier. Kir5.1 is a K+ transporter that plays a significant role in maintaining EP homeostasis, but the expression pattern and role of Kir5.1 (which is encoded by the Kcnj16 gene) in the mouse auditory system has remained unclear. In this study, we found that Kir5.1 was expressed in the mouse cochlea. We checked the inner ear morphology and measured auditory function in Kcnj16–/– mice and found that loss of Kcnj16 did not appear to affect the development of hair cells. There was no significant difference in auditory function between Kcnj16–/– mice and wild-type littermates, although the expression of Kcnma1, Kcnq4, and Kcne1 were significantly decreased in the Kcnj16–/– mice. Additionally, no significant differences were found in the number or distribution of ribbon synapses between the Kcnj16–/– and wild-type mice. In summary, our results suggest that the Kcnj16 gene is not essential for auditory function in mice.

External Ear Features: Role in Tracing Inheritance

Background: The external ear is unique in shape, size and orientation. It has symmetry and asymmetry among generations. Its morphological variation helps to trace genetic inheritance. The objective of this study was to identify this morphological variation among parents and siblings. Methods: The study was conducted in Manipal colleges of medical sciences. Images were procured from 147 families. The morphological character of external ears including, shape of pinnae, concha, tragus, ear lobule and attachment of lobule to cheek were matched among Parents and offspring. Results: This study included 882 pinnae in 147 families. Total 4410 morphological characteristics have been analyzed. Tragus was the most common matching character between parents and offspring Kappa measuring coefficient was statistically significant for shape of pinna, concha, ear lobule, ear lobule attachment to cheek. Conclusions: The most of external ear morphology matches between parents and offspring which may be a helpful tool in tracing hereditary inheritance.