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Icvm-7 Abstracts 274 ICVM-7 ABSTRACTS How to Measure Ontogeny? Expression of beta-Keratin and Its mRNA in Differentiating Lizard Adriaens, Dominique; Ghent University, Gent, Belgium (dominique. Epidermis [email protected]) Alibardi, L.,1 Toni, M.,2 Toffolo, V.,1 and Dalla Valle, L.1; 1University of When studying evolution and adaptations, it is crucial that the early life Bologna, Italy ([email protected]), 2University of Padova, Italy history of vertebrates is considered as well. Selective forces act upon each The hard form of keratin of lizard scales, beta-keratin, was isolated by stage during development, thus constraining developmental processes. electrophoresis after labeling with tritiated proline. The molecular weight When studying ontogeny, developmental age is expressed in different and biosynthesis of beta-keratin was determined by autoradiography and ways: in relation to body size or to (chronological) age. Many discussions immunoblotting showing that the components at 8–10 and 16–18 kDa have tackled this. Deductive models have suggested that size is not a good form most beta-keratins. The primary sequence of beta-keratin was par- measure, because it is linked to shape, which is frequently used as a tially characterized after extraction and selection of a beta-keratin mRNA descriptor of ontogenetic changes. This study is an empirical approach to using RT-PCR. The derived cDNA probe was used to analyze by in situ the problem, using geometric morphometrics. Shape changes in the neu- hybridization the expression of beta-keratin mRNA during epidermal dif- rocranium of the African catfish Clarias gariepinus (Clariidae) are used as ferentiation of lizard epidermis. The probe localizes specifically in cells of a measure of developmental age, and are dissociated from size (using the differentiating beta-layer. Initially, the oberhautchen cells have no generalized procrustes analysis). The obtained shape variables were re- mRNA signal that increases after merging with cells of the beta-layer. This gressed to size (log-transformed standard length) and age (days posthatch- suggests that only beta-cells synthesize beta-keratin mRNA that can be ing), indicating that size is a better measure for ontogeny. Supporting exported into oberhautchen cells during maturation of the beta-layer. evidence is obtained from an experimental setup of two growth series of C. Suprabasal cells with presumptive beta-keratin differentiation show beta- gariepinus larvae, in which the ossification pattern of the skull is in keratin mRNA expression only at stage 3–4 of the shedding cycle, when correspondence with body size and not age. they assume a fusiform shape. This suggests that beta-keratin synthesis is rapidly switched on when presumptive beta-cells reach 2–3 layers above the germinative. This result confirms and details previous morphological and immunocytochemical studies and opens the possibility to completely Promise of Basic Mechanics in Functional and Ecological Vertebrate sequence the expressed beta-keratin mRNA. This will allow deriving the Morphology primary sequence of lizard beta-keratin for further analysis on the molec- Aerts, Peter; University of Antwerp, Belgium ([email protected]) ular evolution of beta-keratins in reptiles. Despite the many prosaic examples of the “perfect fit” between form and function, the underlying causes and adaptive nature (if present) of covaria- tion between design, performance, and ecology are often far from obvious or straightforward. Constraints can make form–function relations much Evolution of Flight Morphology in Hummingbirds more complex than expected at first, or the causal links can just be too Altshuler, Douglas L.,1 Stiles, F. Gary,2 Graves, Gary R.,3 and subtle, even hidden. In order to allow direct focus on the relevant design- McGuire, Jimmy A.4; 1California Institute of Technology, Pasadena, CA, traits, proper deductive assessment of form–function relationships needs an USA ([email protected]), 2Universidad Nacional de Colombia, Colombia, understanding of the demands imposed by the ecology and behavior of the 3National Museum of Natural History, Smithsonian Institution, Washing- organism. Next, insights into the mechanistic coupling between these traits ton, DC, USA, 4University of California, Berkeley, CA, USA and performance can be gained. In the case of musculo-skeletal systems, Hummingbirds are obligate nectarivores and are the only birds capable of biomechanical reasoning and analyses (both through experiments and sustained hovering flight. Despite this high degree of ecological and models) are especially suited to realize these aims: i.e., grasping the logical locomotor specialization, hummingbirds are remarkably diverse, with over sequence from design-traits to differential performance and, finally, to 325 species in the New World, and are also highly variable in body ecological niche. Applied in this way, biomechanical modeling may reveal, morphology, ranging over an order of magnitude difference in body mass. for example, why long limbs are helpful, but not sufficient for the con- Here we analyze the phylogenetic patterns in flight morphology using a spicuous jumping behavior of bush babies; why snake-necked turtles can new phylogeny that contains over 100 taxa based on sequences of one do without long, forceful neck extensors in their fast and precise strike mitochondrial and two nuclear genes. behavior during feeding; why forelimbs are “almost” redundant for fast intermittently running lizards, or why frogs seem to be lazy when swim- ming. Biorhythmical Organization of Spermatogenesis Arav, Vladimir I., Sych, Vitaly F., and Zheleznyak, Elena V.; Ulyanovsk State University, Russia ([email protected]) Air Sac Diverticula as Passive Support Devices in Birds and Sauris- chian Dinosaurs: An Overlooked Biomechanical System We studied the daily dynamics of the mitotic index (MI) of type B Akersten, William A., and Trost, Charles H.; Idaho Museum of Natural spermatogonia and the frequency of spermatogenic cycle stages for intact History, Pocatello, ID, USA ([email protected]) and pinealectomized rats that consequently received an injection of epith- alamin (or the complex of pineal gland neuropeptides). Biorhythms were Just as impermeable and inelastic low-pressure air bladders used in ship- detected through spectral and least-squares (OLS) analyses. The daily MI ping can support up to four tons at 2.0 psi, similar structures in organisms spermatogonia dynamics of intact animals were characterized by a circa- could provide substantial passive support. While portions of the minimally dian rhythm. This rhythm disappeared after pinealectomy but was restored elastic and nearly impermeable diverticula of the air sac complex in birds after the injection of epithalamin between the 26th and 40th day postpi- function to pneumatize bones, other parts play no obvious role in this nealectomy. The spermatogenic cycle of rats comprises 14 stages charac- function. However, their morphologies and placement strongly suggest terized by different combinations of spermatogenic cells. In intact animals, that, upon pressurization, they would provide passive support to much of only 3 of 14 stages that include mitosis of spermatogonia and meiosis of the vertebral column, the femora, and the outstretched wings of soaring spermatocytes had a circadian rhythm. If a given spermatogenic period birds. We observed these effects at inflation pressures of 0.6 Ϯ 0.2 psi. We included several stages, the daily frequency dynamics for this group were focus here on the cervical vertebrae, especially in birds that fly with long also characterized by a circadian rhythm. Pinealectomy led to the disap- extended necks. Avian cervical diverticula consist of anteroposterior pas- pearance of all circadian rhythms and the injection of epithalamin to their sages through the transverse foramina and neural canal, connecting a series restoration. Our study demonstrates the role pineal gland neuropeptides of intervertebral sacs that become progressively smaller craniad. Accessory play in the formation of the spermatogenesis circadian rhythm. Stages of diverticula may also be present. Experimentally pressurizing cervical di- the spermatogenic cycle previously described in the literature seem to verticula demonstrates their role in neck support. Gravitational forces act on the extended necks of flying birds and would similarly affect the necks of saurischians, especially sauropods that held their necks relatively hori- zontally. Because many parallels exist between the pneumatic features of bird and saurischian cervicals, and because major nuchal ligaments are DOI: 10.1002/jmor.10223 absent in both, we infer that saurischian dinosaurs also used pneumatic Published online in pressure to passively support their necks Wiley InterScience (www.interscience.wiley.com) © 2004 WILEY-LISS, INC. ICVM-7 ABSTRACTS 275 reflect the topographic structure of the spermatogenic tissue cells, rather generating traveling waves of lateral undulation after the entire body was than the sequence of spermatogenesis. immersed in water. Surface EMGs Design Principles of Gecko Adhesive Nanostructures Arnold, D., Fischer, M.S., Schumann, N.P., Biedermann, F.H.W., and Autumn, Kellar; Lewis and Clark College, Portland, OR, USA (autumn@ Scholle, H.Ch.; Friedrich-Schiller-University, Jena, Germany (b9ardi@ lclark.edu) pan.zoo.uni-jena.de) Geckos have evolved setal nanostructures on the surface of their toes that Physiological studies with surface-EMGs were undertaken to better under-
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