Mercer Biology

Dr Craig Byron, Assistant Professor

Joined Mercer 2006

office  WSC

phone  478.301.2163

fax  478.301.2067

email  byron_cd@mercer.edu

research page  click here

BIO 202 Human Anatomy and Physiology I

BIO 203 Human Anatomy and Physiology II

BIO 301 Vertebrate Zoology

BIO/ANT 382 Biological Anthropology

BIO 421 Biostatistics and Morphology

Anatomy and Behavior, Functional Morphology, Biological Anthropology

Dr. Byron’s scholarly pursuits can be categorized according to three different types of activities: laboratory-based experiments, fieldwork, and museum studies. A unifying aspect found throughout these activities is an effort to understand how anatomical form relates to organismal behavior. Generally speaking he is interested in this question as it pertains to mammals that live within an arboreal setting. More specifically, he is interested in adaptive aspects of primate locomotion and diet in order to better understand the origins of the order to which we as humans belong. For these reasons his disciplinary identity can be described as a Biological Anthropologist with an emphasis on Functional Morphology.

Dr Byron’s research seeks to elucidate mechanistic pathways that enable skeletal connective tissues to appropriately respond to mechanical stimuli leading to bone growth or bone resorption. By applying a mechanistic understanding to interpreting skeletal morphology, form and function relationships linking organismal behavior to functional anatomy may be clarified. Teaching courses in the anatomical and zoological sciences are of interest to Dr. Byron, especially as they pertain to quantitative methods. A list of these courses includes anatomy and physiology, biostatistics, biological anthropology, and paleontology.

Laboratory Experiments

Experiments in the Byron lab routinely use the mouse as a model organism to study the effects of dietary and locomotor exercise on musculoskeletal anatomy. Behavioral modification is at the root of experimental design so that muscle activity can be either enhanced or diminished. The resulting bone biology is used to validate predictions that emanate from a mechanical understanding of the skeleton.

Dietary exercise is achieved by feeding mice foods with different material properties. Hard food contrasts with soft food in that less time and effort is generally needed to orally process through mastication (i.e., chewing). Relying on foods with increased obduracy (i.e., mechanical difficulty) stimulates an exercise effect of chewing muscles. In turn, a bone growth response in the skull is elicited at muscle attachment points on the cranium and mandible. In general these hard-tissue features are more robust suggesting a functional link between craniofacial robusticity and dietary material properties. In addition to hard tissue features of the skull cranial sutures are also evaluated. These connective tissue ligaments found between individual bones of the skull pattern themselves as interdigitating lines that exhibit self-similar complexity (e.g., fractal geometry). In specimens where increased chewing forces characterize dietary behavior, cranial sutures assume a more complex and waveform pattern.

Locomotor exercise is achieved by running mice on a treadmill at varying speeds or placing them on thin-branch scaffolding which forces a grasping style of cautious above-branch quadrupedalism. Exercise induced muscle growth in these experiments is reflected in skeletal growth at select regions of interest. Specifically, grasping locomotion on thin branches elicits a unique pattern of bone formation due to the exercise of intrinsic hand and foot muscles.

Furthermore, the complex three-dimensional structure of the fine branch niche requires that mice extend, flex, abduct, and adduct limb joints while bridging from one substrate to another.

Field Work

Additional research interest in the Byron lab requires trips to field locations to either observe the behavior of animals in a natural habitat or collect fossils. Behavioral data collection is conducted on arboreal taxa such as tree squirrels because they are locally available and easily observable. These data are useful to assess methods of tree canopy navigation because it is relevant to understanding stages of primate evolution as a radiation of mammals originating as arboreal specialists. Additionally, field studies observing real primates are informative but more difficult to conduct. Other field work I participate in involves collecting fossil material from locations bearing taxa that existed roughly 55 to 35 million years ago. This time period known as the Eocene and Oligocene are important phases in primate evolution as this order is known to diversify into its major groupings throughout these epochs. North America is one continent where this early diversification is especially well-known. Currently Dr. Byron collect fossils with collaborators at the University of Texas in a fossil formation known as the Devil’s Graveyard in SW Texas. He hopes to extend work in this time period into Middle Georgia along what was once a coastal mangrove forest.

Museum Work

This component of my research effort involves traveling to natural history museums to measure specimens that have been curated in their collections. Usually I am interested in obtaining measurements of anatomical morphology and using statistical methods to test hypotheses of functional morphology. These hypotheses relate to dietary and locomotor predictions as related to known ecological observations of the adaptive niche-spaces of these taxa. This work involves traveling to natural history museums, or borrowing materials from the museums, located in cities such as Chicago, New York, Washington DC, and even Paris, France.

Strait DS, Weber GW, Neubauer S, Chalk J, Richmond BG, Lucas PW, Spencer MA, Schrein C, Dechow PC, Ross CF, Grosse IR, Wright BW, Constantino P, Wood BA, Lawn B, Hylander WL, Wang Q, Byron C, Slice DE, Smith AL. (2009) The feeding biomechanics and dietary ecology of Australopithecus africanus. Proceedings of the National Academy of Sciences. 106(7): 2124-2129.

Carlson KJ, Byron CD. (2008) Building a better organismal model: The role of the mouse—Introduction to the symposium. Integrative & Comparative Biology. 48:321-323.

Byron CD, Maness H, Yu J, Hamrick MW. (2008) Enlargement of the Temporalis Muscle and Alterations in the Lateral Cranial Vault. Integrative & Comparative Biology. 48:338-344.

Byron CD, Becker R, Bullard E, Cavin J, Cheek B, Cooper A, DeStevens L, Dunn J, Hooper E, Liendo O, Redmon J, Waynesboro N, Wells C, Wheeler B. (2008) Quantitative Analysis of Litter Composition in a Historic Macon Neighborhood Experiencing Revitalization. Georgia Journal of Science. 66(2):61-71.

Wang Q, Dechow PC, Wright BW, Ross CF, Strait DS, Richmond BG, Spencer MA, Byron CD. (2008) Surface strain on bone and sutures in a monkey facial skeleton: an in vitro approach and its relevance to Finite Element Analysis. In Vinyard CJ, Ravosa MJ and Wall CE (eds): Primate Craniofacial Function and Biology, Development in Primatology Series. New York: Springer, pp.149-172.

Vecchione L, Byron C, Cooper GM, Barbano T, Hamrick MW, Sciote JJ, Mooney MP. (2007) Craniofacial Morphology in Myostatin-Deficient Mice. Journal of Dental Research. 86(11):1068-1072.

Byron CD. (2006) The role of the osteoclast in cranial suture waveform patterning. The Anatomical Record Part A. 288A:552–563.

Byron CD, Hamrick M, Wingard C. (2005) Alterations of temporalis muscle contractile force and histological content from the myostatin and Mdx deficient mouse. Archives of Oral Biology. 51(5): 396-405.

Byron CD, Covert HH. (2004) Unexpected Locomotor Behavior: Brachiation by an Old World Monkey from Vietnam. Journal of Zoology. 263(1):101-106.

Byron CD, Borke J, Yu J, Pashley D, Wingard C, Hamrick M. (2004) The effects of increased muscle mass on mouse sagittal suture morphology and mechanics. The Anatomical Record Part A. 279A: 676-684.

Covert HH, Workman C, Byron C. (2004) The EPRC as an important research center: ontogeny of locomotor differences among Vietnamese colobines. In: Conservation of Primates in Vietnam, edited by Nadler T, Streicher U and Long HT. Hanoi: Frankfurt Zoological Society and Haki Publishing, p. 121-129.

Hamrick MW, Pennington C, Byron C .(2003) Bone architecture and disc degeneration in the lumbar spine of mice lacking GDF-8 (myostatin). Journal of Orthopaedic Research. 21:1025-1032.