Christopher Bernhardt (MS, 2000) led a study on ancient climates of Alexandria, profiled by MSNBC at
http://www.msnbc.msn.com/id/33453098/ns/technology_and_science-science/
The winter plant science bulletin has a memorium article about Dr. Walter Macior (former UA Distinguished Professor in Biology), written by one of his UA students (Bruce Robart). Please see the article HERE
Agnarsson et al.’s recent manuscript has made the cover of the Journal of Experimental Zoology.
Agnarsson I, Boutry C, Blackledge TA, 2008. Spider silk aging: Initial improvement in a high performance material followed by slow degradation. J Exp Zool 309A:494-504.
The Biology Department started a new assessment program this Fall, aimed at measuring gains in Biology-specific knowledge over the course of a student’s college career. Students in their first semester as Biology majors took a short online quiz that covered many areas of Biology. Their scores will be compared with students in their last semester before they graduate, and we will use the results to inform and improve Biology teaching. Brittany Lesher (pictured) had the highest score on this first round of quizzes, and for her outstanding effort she was awarded an IPOD ITOUCH music player. Congratulations Brittany!
The research of Dr. Todd Blackledge was profiled on the font page of the UA web site today. To see the full story click HERE
- Tom Jones received his BS in Biology from UA and his MS degree from UA under Dr. Ely in 1997. Currently, he was just hired as an Asst. Prof of Pharmacology at NEOUCOM.
- Dr. Jonathan Toot- PhD in 2007 from KSU/UA/NEOUCOM and is working as a research scientist for Wil Labs in Ashland Ohio in Neurotoxicology.
-Dr. Christine Spahn rec her MS from UA under Dr. Ely, 2004 and in June, 2008 rec,. her MD from NEOUCOM and has started a residency in Surgery at Summa.
UA Biology Professor Randy Mitchell co-organized a two-day conference on the Ecology and Evolution of Plant-Pollinator Interactions, held in conjuction with the National Meeting of the Ecological Society of America in Milwaukee, Wisconsin. This conference highlighted the most exciting recent advances in community and evolutionary pollination biology, fostering interactions among pollination biologists. The conference aimed to encourage a unified framework for community and evolutionary approaches to pollination, and to draw attention to largely unexplored questions at the intersection of these disciplines. This two-day conference (August 2-3, 2008) featured 23 speakers from five continents and eight countries, a poster session with over 80 entries, and over 200 registered participants. More information can be found at the conference website: www.uakron.edu/biology/pollination
Below are some publications from just the past few months by faculty and students from the UA Department of Biology. (UA biology members are in bold)
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2008. Bernhardt CE, RJ Mitchell, HJ Michaels. Effects of population size and density on pollinator visitation, pollinator behaviour, and pollen tube abundance in Lupinus perennis. International Journal of Plant Sciences 169: 944-953.
Abstract: Both the number and the density of flowering plants in a population can be important determinants of pollinator abundance and behavior. We report the joint effects of population size and density on pollinator visitation and pollination success for Lupinus perennis (Fabaceae). Focusing on five pairs of populations, we matched one small population (125–800 flowering plants) with one distinctly larger population (1000–3000 flowering plants). In these pairs, population size did not affect pollinator communities or pollination success. All measures of pollination success increased significantly with density. Only bee behavior (number of flowers probed per inflorescence) exhibited a significant interaction of size and density. Testing whether population sizes smaller than those in the paired populations might affect pollination, we gathered pollen tube samples from 14 unpaired populations (16–215 flowering plants). Combining these data with those from the paired populations revealed a significant decrease in pollination for smaller populations, indicating that effects of population size may be detectable only when populations smaller than a few hundred plants are sampled. We found that effects of density are consistent and much stronger than those of population size. Our results suggest that both size and density of natural populations should be considered in designing restoration and reintroduction programs for this threatened plant.
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Dev Neurobiol. 2008 Jul;68(8):1107-22. Cadherin-6 function in zebrafish retinal development.Liu Q, Londraville R, Marrs JA, Wilson AL, Mbimba T, Murakami T, Kubota F, Zheng W, Fatkins DG.
Department of Biology, University of Akron, Akron, OH 44325, USA. qliu@uakron.edu
Abstract: Cadherin cell-adhesion molecules play crucial roles in vertebrate development including the development of the visual system. Most studies have focused on examining functions of classical type I cadherins (e.g., cadherin-2) in visual system development. There is little information on the function of classical type II cadherins (e.g., cadherin-6) in the development of the vertebrate visual system. To gain insight into cadherin-6 role in the formation of the retina, we analyzed differentiation of retinal ganglion cells (RGCs), amacrine cells, and photoreceptors in zebrafish embryos injected with cadherin-6 specific antisense morpholino oligonucleotides. Differentiation of the retinal neurons in cadherin-6 knockdown embryos (cdh6 morphants) was analyzed using multiple markers. We found that expression of transcription factors important for retinal development was greatly reduced, and expression of Notch-Delta genes and proneural gene ath5 was altered in the cdh6 morphant retina. The retinal lamination was present in the morphants, although the morphant eyes were significantly smaller than control embryos due mainly to decreased cell proliferation. Differentiation of the RGCs, amacrine cells, and photoreceptors was severely disrupted in the cdh6 morphants due to a significant delay in neural differentiation. Our results suggest that cadherin-6 plays an important role in the normal formation of the zebrafish retina. (c) 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008. (Copyright) 2008 Wiley Periodicals, Inc.
Cell Tissue Res. 2008 Jul 30. [Epub ahead of print] Cadherin-7 function in zebrafish development.Liu Q, Marrs JA, Londraville RL, Wilson AL. Department of Biology, University of Akron, Akron, OH 44325, USA, qliu@uakron.edu.
Abstract: Cadherin cell adhesion molecules play crucial roles in vertebrate development. Most studies have focused on examining the functions of classical type I cadherins (e.g., cadherin-2) in the development of vertebrates. Little information is available concerning the function of classical type II cadherins (e.g., cadherin-7) in vertebrate development. We have previously shown that cadherin-7 mRNA exhibits a dynamic expression pattern in the central nervous system and notochord in embryonic zebrafish. To gain insight into the role of cadherin-7 in the formation of these structures, we analyzed their formation in zebrafish embryos injected with cadherin-7-specific antisense morpholino oligonucleotides (MO). Notochord development was severely disrupted in MO-injected embryos, whereas gross defects in the development of the central nervous system were not detected in MO-injected embryos. Our results thus demonstrate that cadherin-7 plays an important role in the normal development of the zebrafish notochord.
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Sticky Gecko Feet: The Role of Temperature and Humidity
Peter H. Niewiarowski1*, Stephanie Lopez1, Liehui Ge2, Emily Hagan2, Ali Dhinojwala2 1 Department of Biology, Program in Integrated Bioscience, University of Akron, Akron, Ohio, United States of America, 2 Department of Polymer Science, University of Akron, Akron, Ohio, United States of America.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002192
Abstract: Gecko adhesion is expected to be temperature insensitive over the range of temperatures typically experienced by geckos. Previous work is limited and equivocal on whether this expectation holds. We tested the temperature dependence of adhesion in Tokay and Day geckos and found that clinging ability at 12°C was nearly double the clinging ability at 32°C. However, rather than confirming a simple temperature effect, our data reveal a complex interaction between temperature and humidity that can drive differences in adhesion by as much as two-fold. Our findings have important implications for inferences about the mechanisms underlying the exceptional clinging capabilities of geckos, including whether performance of free-ranging animals is based solely on a dry adhesive model. An understanding of the relative contributions of van der Waals interactions and how humidity and temperature variation affects clinging capacities will be required to test hypotheses about the evolution of gecko toepads and is relevant to the design and manufacture of synthetic mimics.
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Shawkey et al.. 2008. Do birds differentially distribute antimicrobial proteins within clutches of eggs? Behavioral Ecology 19:920-927 http://beheco.oxfordjournals.org/current.dtl
Summary: Eggs contain multiple defenses against microbial infection of developing embryos, including incubation behaviors of parents and numerous antimicrobial proteins in egg white. When eggs are not incubated, microbes multiply rapidly on their shells, and can penetrate to the egg interior and cause infection and death of embryos. Birds typically lay one egg a day, and earlier-laid eggs frequently sit unincubated for several days until parents begin fully incubating them. Because these earlier-laid eggs are at greater risk for microbial infection than later-laid eggs, we hypothesized that they would contain higher levels of antimicrobial proteins. We tested this hypothesis by collecting complete clutches of eggs from eight species of birds and measuring concentrations of 3 antimicrobial proteins in each egg. Concentration of antimicrobial proteins largely did not differ between eggs within clutches of each species and thus, our hypothesis was not supported. Birds may deposit similar concentrations of proteins in all eggs regardless of laying order because these proteins are physiologically cheap to produce.
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Siefferman, Shawkey et al. 2008. Juvenile coloration of Florida Scrub-Jays (Aphelocoma coerulescens) is sexually dichromatic and correlated with condition Journal of Ornithology 149:357-363. http://www.springerlink.com/content/hj7rl14613h17304/
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2008. Michaels HJ, XJ Shi, RJ Mitchell. Effects of population size on performance and inbreeding depression in Lupinus perennis. Oecologia 154:651-661.
We investigated the relationships among population size, offspring performance, and inbreeding depression (δ) in Lupinus perennis by examining the effect of population size category (large vs. small) on seed production and offspring performance for three pollination treatments (open pollination, hand crossing and hand selfing). In each of our four pairs of populations, one member of the pair was substantially larger than the other. We then grew seeds from this factorial design (2 sizes x 4 pairs x 3 pollination treatments) in the greenhouse to investigate whether population size affects offspring performance in a common environment, and how small size affects purging of the inbreeding load. Multiplicative performance across four early life-stage components (seed production, seedling emergence, seedling survival and seedling growth) of smaller populations was not significantly lower, although biomass of seedlings declined in smaller populations. Self-pollination reduced seed production, seedling emergence and seedling growth, reflecting substantial inbreeding depression (δ = 0.404 ± 0.043). Population size categories did not consistently differ in levels of inbreeding depression, suggesting that purging of genetic load in smaller populations has been limited, and that all populations still harbor inbreeding load. We also found a significant decrease in log performance with increases in the population inbreeding coefficient. These results indicate that even in seemingly large populations, lupines are susceptible to considerable fitness declines through both inbreeding load within populations, and drift load via genetic erosion and fixation of deleterious alleles between populations.
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2008. Mitchell, RJ, TL Ashman. Predicting the evolutionary consequences of pollinator declines: the long and short of floral evolution. New Phytologist. 177:576-579
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Zevenbergen JM, Schneider NK, Blackledge TA, 2008. Fine dining or fortress? Functional shifts in spider web architecture by the western black widow Latrodectus hesperus. Anim Behav 76:823-829. (Highlighted by New Scientist)
Spiders alter web architecture in response to many environmental factors. Yet, the functional implications of this behavioural plasticity are poorly understood, especially for spiders that spin long-lasting webs such as cobwebs. The western black widow spins a three-dimensional web that captures terrestrial prey and can persist for many days. However, the shape of the cobweb depends upon changes in the spider’s body condition. Starved spiders invest more silk in sticky gumfooted threads, whereas sated spiders invest more silk in supporting threads.We tested the hypothesis that the increased investment in sticky gumfooted threads by starved spiders functions to improve the prey capture of their webs. Regardless of intrinsic foraging motivation, both fed and starved spiders captured more prey, more quickly and more efficiently, when hunting on a web that was spun by a starved spider. Our study shows that cobweb spiders actively manipulate web-spinning behaviours in ways that alter the functions of their webs and that even spiders spinning relatively long-lasting webs may use behavioural plasticity to respond to changing selective pressures in their environment.
Agnarrson I, Boutry C, Blackledge TA, 2008. Spider silk aging: Initial improvement in a high performance material followed by slow degradation. J Exp Zool 309A: 494-504.
Spider silk possesses a unique combination of high tensile strength and elasticity resulting in extraordinarily tough fibers, compared with the best synthetic materials. However, the potential application of spider silk and biomimetic fibers depends upon retention of their high performance under a variety of conditions. Here, we report on changes in the mechanical properties of dragline and capture silk fibers from several spider species over periods up to 4 years of benign aging. We find an improvement in mechanical performance of silk fibers during the first year of aging. Fibers rapidly decrease in diameter, suggesting an increase in structural alignment and organization of molecules. One-year old silk also is stiffer and has higher stress at yield than fresh silk, whereas breaking force, elasticity, and toughness either improve or are unaffected by early aging. However, 4-year old silk shows signs of degradation as the breaking load, elasticity, and toughness are all lower than in fresh silk. Aging, however, does not reduce the tensile strength of silk. These data suggest initially rapid reorganization and tighter packaging of molecules within the fiber, followed by longer-term decomposition. We hypothesize that possibly the breakdown of amino acids via emission of ammonia gas, as is seen in long-term aging of museum silkworm fabrics, may contribute. Degradation of spider silk under benign conditions may be a concern for efforts to construct and utilize biomimetic silk analogs. However, our findings suggest an initial improvement in mechanical performance and that even old spider silk still retains impressive mechanical performance.
Boutry C, Blackledge TA, 2008. The common house spider alters the material and mechanical properties of cobweb silk in response to different prey. J Exp Zool 309A:in press. (Highlighted in National Geographic News)
Many spiders depend upon webs to capture prey. Web function results from architecture and mechanical performance of the silk. We hypothesized that the common house spider, Achaearanea tepidariorum, would alter the mechanical performance of its cobweb in response to different prey by varying the structural and material properties of its silk. We fed spiders either large, high kinetic energy crickets or small, low kinetic energy pillbugs for 1 week and then examined their freshly spun silk. We separated mechanical performance into structural and material effects. We measured both types of properties for silk threads collected directly from cobwebs to test for ‘‘tuning’’ of silk performance to different aspects of prey capture. We compared silk from two different functional regions of the cobweb—sticky gumfooted threads that adhere directly to prey and supporting threads that maintain web integrity. Supporting threads from cricket-fed spiders were stiffer and tougher than supporting threads from pillbug-fed spiders. Both types of silk from cricket-fed spiders broke at higher loads than silk from pillbug-fed spiders. We explain this variation using a simple model of forces exerted by prey and spiders on single threads and propose potential mechanisms for this change in material properties. Two alternative, nonexclusive, hypotheses are suggested by our data. Spiders may tune silk to different types of prey by spinning threads that are able to hold prey without deforming permanently. Alternatively, as spider’s body mass differed dramatically between the two feeding regimes, spiders may tune silk to their own body mass.
Agnarsson, I., May-Collado, L.J., The phylogeny of Cetartiodactyla: The importance of dense taxon sampling, missing data, and the remarkable promise of cytochrome b to provide reliablespecies-level phylogenies , Mol. Phylogenet. Evol. (2008), doi:10.1016/j.ympev.2008.05.046
Ingi Agnarsson and Jeremy Miller. 2008. Is ACCTRAN better than DELTRAN? Cladistics 24:1-7
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Renzaglia, K. S., J. C. Villarreal A., and R. Joel Duff. 2008 (December). New insights into morphology, anatomy, and systematics of hornworts. In “Bryophyte Biology, Vol II” (Eds. Shaw and Goffinett). 2008. Cambridge MA.
R. Joel Duff, H. Ball, and P. J. Lavrentyev. 2008. Application of combined morphological-molecular approaches to the identification of planktonic protists from environmental samples. J. Eukaryot. Microbiol. In Press
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Toot J,Jenkins C, Dunphy G,Boehme S, Hart M, Milsted A, Turner M, Ely D. Testosterone influences renal electrolyte excretion in SHR/y and WKY males. BMC Physiology 8:5,2008.
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Jacki Zevenbergen’s MS thesis, published in Animal Behaviour, was recently highlighted in the New Scientist. Jacki recieved here MS in 2007 under the direction of Dr. Todd Blackledge (UA Biology). Read the article here:
http://www.newscientist.com/channel/life/mg19826625.600-hungry-spiders-spin-deadlier-webs.html
Dr. Beverly Brown will receive the Charles Edwin Bessey Teaching Award. In honor of Charles Edwin Bessey, this award recognizes outstanding contributions made to botanical instruction. This award will be given out at the annual Botanical Society of America meeting this coming August. Dr. Brown was a Ph.D student of Dr. Randy Mitchell (UA Biology) through Kent State. She also received her MS degree from the University of Akron.
Congratulations Dr. Brown!