Anatomical and Physiological Characterization of the Turtle Brain Stem Auditory Circuit

The goal of this dissertation is to add to understanding of the evolution of hearing by studying the testudine taxon. This dissertation focuses on central auditory processing in the context of evolution. The experiments described are designed to give insight into how binaural hearing evolved. Follow the findings of Christensen-Dalsgaard and colleagues (2012) that an amphibious turtle had lower hearing thresholds under water than in air and that this difference is conferred by resonance of the middle ear cavity, I examined middle ear cavities across families of Testudines. I found that middle ear cavity structure and function is shared by all testudines (Willis, et al., 2013). Modern neuroanatomical tract tracing techniques were used to understand the connections among the auditory nuclei in the brain stem of the turtle. Turtles have brain stem nuclei that are connected in the same pattern as the other reptiles, including birds. These nuclei are nucleus angularis, nucleus magnocellularis, nucleus laminaris, superior olive, and torus semicircularis. Details of neuron structure were also examined and quantified. Finally, I developed an isolated head preparation that enables in vivo-like physiological recording. As proof of principle, neurons were characterized by best frequency response, threshold, phase locking. Additionally, binaurally responsive neurons were found, which have a range of interaural time difference sensitivity responses. Although the evolutionary position of testudines is not yet resolved, it is most likely that testudines share their most recent common ancestor with the archosaurs. I hypothesize that testudines likely reflect the ancestral condition of auditory processing for the archosaur clade. All experiments described in this dissertation were performed according to the guidelines approved by the Marine Biological Laboratory (Woods Hole, MA, USA), the University of Maryland Institutional Animal Care and Use Committees (IACUC) and the Danish National Animal Experimentation Board (Dyreforsøgstilsynet)

Flexibility within the middle ears of vertebrates

Introduction and aims: Tympanic middle ears have evolved multiple times independently among vertebrates, and share common features. We review flexibility within tympanic middle ears and consider its physiological and clinical implications. Comparative anatomy: The chain of conducting elements is flexible: even the ‘single ossicle’ ears of most non-mammalian tetrapods are functionally ‘double ossicle’ ears due to mobile articulations between the stapes and extrastapes; there may also be bending within individual elements. Simple models: Simple models suggest that flexibility will generally reduce the transmission of sound energy through the middle ear, although in certain theoretical situations flexibility within or between conducting elements might improve transmission. The most obvious role of middle-ear flexibility is to protect the inner ear from high-amplitude displacements. Clinical implications: Inter-ossicular joint dysfunction is associated with a number of pathologies in humans. We examine attempts to improve prosthesis design by incorporating flexible components

The characteristics and affinities of the Amphisbaenia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75528/1/j.1096-3642.1978.tb00376.x.pd

Studies Of Sound Propagation In The Acoustic Trachea: An Experimental, Anatomical And Numerical Approach

Bush-crickets (Ensifera: Tettigoniidae) rely on the perception of sound to detect and localise predators and potential mates, and this has led to the development of complex ears. This is not confined to bush-crickets, and a variety of sound detection and localisation mechanisms have arisen in other ensiferans and tetrapods. This thesis aims to summarise the literature across these two groups to provide an overview of auditory anatomy and directional hearing. Bush-crickets possess ears in their forelegs to detect and localise sound predators and potential mates. Each ear consists of two tympanic membranes which are exposed to sound both externally, where sound transmits to the ear through the environment, and internally, via an ear canal derived from the respiratory system. As sound propagates through the ear canal it reduces in velocity, causing a time delay between the arrival of the internal and external input. The delay was suspected to arise as sound propagation changes from adiabatic to isothermal, caused by the ear canal geometry. If true, then the reduction in sound velocity should persist independently of the gas composition in the ear canal. This method was first simulated on a simplified plastic model of the ear canal, formed by a linear tube with an opening at one end for sound input, and a balloon membrane at the other for sound reception. A probe-loudspeaker was used to project a signal into the linear tube, and laser Doppler vibrometer recorded the arrival time of the signal at the membrane. A reduction in sound propagation velocity was observed in the linear tube. The sound propagation velocity through air and carbon dioxide was also quantified. Experiments were then conducted on specimens of Copiphora gorgonensis. By integrating laser Doppler vibrometry, micro-CT scanning, and numerical analysis on 3D geometries of each experimental animal ear, we demonstrate that the narrowing radius of the ear canal is the main factor reducing sound velocity. The numerical simulations of the sound propagation use the precise 3D geometry of the ear canal and take into account the viscous and thermal boundary layers formed near the wall of the ear canal; whose thickness also depend on the tube radius. Likewise, the ear canal is asymmetrically bifurcated at the tympana organ location (one branch for each tympanic membrane) creating two additional internal sound paths and imposing different sound velocities for each tympanic membrane. Therefore, external and internal inputs add up to four auditory paths for each ear (to compare, only one for humans). Implication of findings in avian directional hearing and potential applications in acoustic triangulation devices are discussed

The Braincase and Neurosensory Anatomy of an Early Jurassic Marine Crocodylomorph: Implications for Crocodylian Sinus Evolution and Sensory Transitions

This is the pre-peer reviewed version of the following article: Brusatte, S. L., Muir, A. , Young, M. T., Walsh, S. , Steel, L. and Witmer, L. M. (2016), The Braincase and Neurosensory Anatomy of an Early Jurassic Marine Crocodylomorph: Implications for Crocodylian Sinus Evolution and Sensory Transitions. Anat. Rec., 299: 1511-1530., which has been published in final form at doi:10.1002/ar.23462. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving." You are advised to consult the published version if you wish to cite from it

Braincase and endocranial anatomy of two thalattosuchian crocodylomorphs and their relevance in understanding their adaptations to the marine environment

Thalattosuchians are a group of Mesozoic crocodylomorphs known from aquatic deposits of the Early Jurassic-Early Cretaceous that comprises two main lineages of almost exclusively marine forms, Teleosauridae and Metriorhynchoidea. Teleosaurids were found in shallow marine, brackish and freshwater deposits, and have been characterized as semiaquatic near-shore forms, whereas metriorhynchids are a lineage of fully pelagic forms, supported by a large set of morphological characters of the skull and postcranial anatomy. Recent contributions on Thalattosuchia have been focused on the study of the endocranial anatomy. This newly available information provides novel evidence to suggest adaptations on the neuroanatomy, senses organs, vasculature, and behavioral evolution of these crocodylomorphs. However, is still not clear if the major morphological differences between teleosaurids and metriorhynchids were also mirrored by changes in the braincase and endocranial anatomy. Based on X-ray CT scanning and digital endocast reconstructions we describe the braincase and endocranial anatomy of two well-preserved specimens of Thalattosuchia, the semiaquatic teleosaurid Steneosaurus bollensis and the pelagic metriorhynchid Cricosaurus araucanensis. We propose that some morphological traits, such as: an enlarged foramen for the internal carotid artery, a carotid foramen ventral to the occipital condyle, a single CN XII foramen, absence of brain flexures, well-developed cephalic vascular system, lack ofsubtympanic foramina and the reduction of the paratympanic sinus system, are distinctive features of Thalattosuchia. It has been previously suggested that the enlarged foramen for the internal carotid artery, the absence of brain flexures, and the hypertrophied cephalic vascular system were synapomorphies of Metriorhynchidae; however, new information revealed that all of these features were already established at the base of Thalattosuchia and might have been exapted later on their evolutionary history. Also, we recognized some differences within Thalattosuchia that previously have not been received attention or even were overlooked (e.g., circular/bilobate trigeminal foramen, single/double CN XII foramen, separation of the cranioquadrate canal from the external otic apertureFacultad de Ciencias Naturales y Muse

Applied Nutritional Studies With Zoological Reptiles

The first clinical case evaluated the body condition estimates of Brothers Island Tuatara (Sphenodon guntheri) housed at the San Diego Zoo to that of the wild. The tuataras that are cared for by the San Diego Zoo (SDZ) are larger and have a greater conditioning score than that of the tuataras sampled in the wild. Over the 9 year period of sampling the SDZ tuatara had a mean increase in mass of 125.2 %, SVL of 31.7 %, and BCE of 7.5%. The second clinical case evaluated ascorbic acid, vitamin E, vitamin A, and trace elements in serum of zoo crocodilians. For the 20 individuals from four species (Alligator mississippiensis; Alligator sinensis; Crococdylus johnsoni; and Gavialis gangeticus), serum nutrient concentrations averaged 11.06 mg Ca/dl, 91.66 ?g Cu/dl, 36.88 ?g Fe/dl, 2.86 mg Mg/dl, 4.03 mg P/dl, 3.97 mEq K/L, 153.88 mEq Ma/L, 41.43 mg Zn/dl, 0.50 ?g vitamin A/dl, 46.70 ?g vitamin E/dl, and 0.66 mg ascorbic acid/dl. The third study evaluated the nutrient composition of banana tree (Musa sp.) leaf, petiole, and pseudo-stem at the San Diego Zoo. In a zoo environment, different banana tree components are commonly fed to various animals. At the San Diego Zoo, banana tree (Musa sp.) petiole and leaves are part of the gorillas� (Gorilla gorilla gorilla) browse rotation, and the pseudo-stem is fed once weekly to the Galapagos tortoises (Chelonoidis nigra). Knowing nutritional composition of different banana tree components can improve diet formulation for captive zoo animals. For this study, the length, weight, and nutritional composition of banana tree, leaves, petiole, and pseudo-stems was analyzed. The last study compared the estimated digestibility of two commercially-available herbivorous tortoise pellets versus historic San Diego Zoo Global diets. Trial 1 consisted of a series of digestibility trials on produce-based and commercial pelleted diets, using animals in the SDZG collection. Trial 2 examined the same range of information in a more controlled fashion by simulating the herbivorous tortoise�s digestive system within a test tube. The results may be used to improve husbandry at zoos and to better educate pet owners on appropriate care of their companions.Animal Scienc

Eleutherodactylus ridens (Pygmy Rainfrog) Predation

Workers of the large ponerine ant Paraponera clavata typically forage on small to medium-sized arthropods or collect pieces of plants or nectar but have been suspected of predating small vertebrates