Applied Comparative Anatomy of the Avian Middle Ear

Comparative morphology of the avian bony columella

In birds, the columella is the only bony element of the sound conducting apparatus, conveying vibrations of the cartilaginous extracolumella to the fluid of the inner ear. Although avian columellar morphology has attracted some attention over the past century, it nonetheless remains poorly described in the literature. The few existing studies mostly focus on morphological descriptions in relatively few taxa, with no taxonomically broad surveys yet published. Here we use observations of columellae from 401 extant bird species to provide a comprehensive survey of columellar morphology in a phylogenetic context. We describe the columellae of several taxa for the first time and identify derived morphologies characterizing higher-level clades based on current phylogenies. In particular, we identify a derived columellar morphology diagnosing a major subclade of Accipitridae. Within Suliformes, we find that Fregatidae, Sulidae, and Phalacrocoracidae share a derived morphology that is absent in Anhingidae, suggesting a secondary reversal. Phylogenetically informed comparisons allow recognition of instances of homoplasy, including the distinctive bulbous columellae in suboscine passerines and taxa belonging to Eucavitaves, and bulging footplates that appear to have evolved at least twice independently in Strigiformes. We consider phylogenetic and functional factors influencing avian columellar morphology, finding that aquatic birds possess small footplates relative to columellar length, possibly related to hearing function in aquatic habitats. By contrast, the functional significance of the distinctive bulbous basal ends of the columellae of certain arboreal landbird taxa remains elusive.

The Role of Sound in Livestock Farming-Selected Aspects

To ensure the optimal living conditions of farm animals, it is essential to understand how their senses work and the way in which they perceive their environment. Most animals have a different hearing range compared to humans; thus, some aversive sounds may go unnoticed by caretakers. The auditory pathways may act through the nervous system on the cardiovascular, gastrointestinal, endocrine, and immune systems. Therefore, noise may lead to behavioral activation (arousal), pain, and sleep disorders. Sounds on farms may be produced by machines, humans, or animals themselves. It is worth noting that vocalization may be very informative to the breeder as it is an expression of an emotional state. This information can be highly beneficial in maintaining a high level of livestock welfare. Moreover, understanding learning theory, conditioning, and the potential benefits of certain sounds can guide the deliberate use of techniques in farm management to reduce the aversiveness of certain events.

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

Otological studies rely on a lot of data drawn from animal studies. A lot of pathological or evolutionary questions may find answers in studies on primates, providing insights into the morphological, pathological, and physiological aspects of systematic biological studies. Our study on auditory ossicles moves from a pure morphological (macroscopic and microscopic) investigation of auditory ossicles to the morphometrical evaluation of several individuals as well as to some interpretative data regarding some functional aspects drawn from these investigations. Particularities from this perspective blend with metric data and point toward comparative elements that might also serve as an important reference in further morphologic and comparative studies.

Morphological and morphometrical study of the auditory ossicles in chinchilla

This study is meant to illustrate and describe the features of the auditory ossicles of the chinchilla (Chinchilla lanigera), one of the species used more and more frequently in otology and ear surgery as animal model. Cephalic extremities of 12 C. lanigera individuals obtained from a private farm, where this species was bred for fur, were used in this study. The ossicles were obtained either by direct surgical harvesting by mastoid approach or after a dermestid beetle exposure followed by anatomical dissection. The three ossicles that form the assembly are the malleus, incus and stapes. After the removal of these ossicles, a series of anatomical descriptions were made, followed by seriate sets of measurements. The malleus and incus form a joined-single unit called the maleo-incal complex, with an elongated straight appearance, also due to the development of the anterior process. The handle of the malleus and the long process of incus are almost perpendicular to the main axis of the maleo-incal complex. The presence of the muscular process on the handle of the malleus is recorded. The overall shape of the incus is given by the uneven development of the two processes and the reduced neck part. The stapes is the smallest of the components that maintains the well-known architecture in accordance with the general model. The morphology of all three ossicles is backed by a series of measurements, some standard, some adapted to the morphology of the ossicles. From the very reduced comparative metrical data at our disposal, our study presents an average of 10% lower values for the ones presented earlier by other researchers in the same species.

The lessons of middle-ear function in non-mammals: improving columellar prostheses

Due to the simplicity of their manufacture and placement, middle-ear prostheses are generally constructed using only a single 'ossicle'. The variety of pathologies frequently make it necessary to devise individual solutions and the results are often unsatisfactory. Many methods of improving the prostheses have been tried, with very mixed results. Even until recently, the fundamental assumptions underlying the use of single-ossicle, or columellar, prosthesis have been questioned, with suggestions that this type of prosthesis should be abandoned in favour of attempts to reconstruct a true three-ossicle middle ear. As some of the assumptions in the literature regarding columellar middle ears are incorrect and some published information is not easily accessible, a brief review of pertinent details of non-mammalian systems is given here.