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Janesville, WI, United States

Levine T.D.,Murray State University | Levine T.D.,University of Wisconsin Rock County | Hansen H.B.,Nebraska Wesleyan University | Gerald G.W.,Nebraska Wesleyan University
Biological Journal of the Linnean Society

Because of the sedentary lifestyle of freshwater mussels, studies examining their movement capabilities are scarce. However, the ability to burrow into the substrate and the ability to remain stationary are likely crucial components of their behavioural repertoire. The performance of these different tasks is likely to be affected by the presence of the shell ornamentation characteristic of many mussel species. Previous studies have suggested that shell ornamentation results in a trade-off between burrowing ability and remaining stationary when an extrinsic force attempts to dislodge it from the substrate once buried. We examined the effect of morphology and shell ornamentation on burrowing performance and anchoring ability by artificially creating shell ornamentation on a relatively smooth-shelled species (Potamilus alatus). Burrowing behaviours and performance and the force required to dislodge mussels (anchoring ability) were quantified with and without ornamentation. Interestingly, we found that the artificial shell ornamentation had no significant effect on burrowing behaviours and performance or dislodgement force. Burrowing and dislodgement, however, were both highly influenced by shell size and shape. All of the available information suggests that shell size, shape, and sculpture influence burrowing and anchoring in complex ways that needs further examination. © 2013 The Linnean Society of London. Source

Klubertanz T.H.,University of Wisconsin Rock County
Entomological News

Seven new state and sixty-four new county records of mayflies (Insecta: Ephemeroptera) are given for Illinois, Iowa, Michigan, Minnesota, Missouri, and Nebraska based upon review of existing collections as well as newly collected material. New state records are provided for Baetis brunneicolor (Baetidae), Iswaeon anoka (Baetidae), Procloeon fragile (Baetidae), Pseudocentroptiloides usa (Baetidae), Cercobrachys lilliei (Caenidae), and Heptagenia whitingi (Heptageniidae). Source

Fleischmann J.A.,University of Wisconsin Rock County | Plesha M.E.,University of Wisconsin - Madison | Drugan W.J.,University of Wisconsin - Madison
Geotechnical and Geological Engineering

We perform numerical simulations using the discrete element method (DEM) to determine yield surfaces for large samples of randomly packed uniform spheres with constant normal and tangential contact stiffnesses (linear spring model) and uniform inter-particle friction coefficient μ, for a large range of values of the inter-particle friction coefficient μ. The beauty of DEM is that the micromechanical properties of the spheres, especially the inter-particle friction coefficient μ, are known exactly. Further, simulations can be performed with particle rotation either prohibited or unrestrained, which provides an effective means for evaluating analytical models that employ these assumptions. We compare the resulting yield surfaces to the Mohr-Coulomb, Matsuoka-Nakai, Lade-Duncan, and Drucker-Prager yield surfaces, and determine the relationship between the resulting material friction angle φ{symbol} on the macroscale and the inter-particle friction coefficient μ (or the inter-particle friction angle φ{symbol}μ) on the microscale. We find the Lade-Duncan yield surface provides the best agreement, by far, with the simulations in all cases. We also monitor inter-particle friction work and particle rotation within each specimen during the DEM simulations, both globally and on a particle-by-particle basis, and we compare the results obtained from DEM simulations in which the spheres were allowed full three-dimensional translational and rotational freedom of motion and DEM simulations in which particle rotation was prohibited. © 2014 Springer International Publishing Switzerland. Source

Suen G.,University of Wisconsin - Madison | Teiling C.,Roche Holding AG | Li L.,Life science 454 | Holt C.,University of Utah | And 48 more authors.
PLoS Genetics

Leaf-cutter ants are one of the most important herbivorous insects in the Neotropics, harvesting vast quantities of fresh leaf material. The ants use leaves to cultivate a fungus that serves as the colony's primary food source. This obligate ant-fungus mutualism is one of the few occurrences of farming by non-humans and likely facilitated the formation of their massive colonies. Mature leaf-cutter ant colonies contain millions of workers ranging in size from small garden tenders to large soldiers, resulting in one of the most complex polymorphic caste systems within ants. To begin uncovering the genomic underpinnings of this system, we sequenced the genome of Atta cephalotes using 454 pyrosequencing. One prediction from this ant's lifestyle is that it has undergone genetic modifications that reflect its obligate dependence on the fungus for nutrients. Analysis of this genome sequence is consistent with this hypothesis, as we find evidence for reductions in genes related to nutrient acquisition. These include extensive reductions in serine proteases (which are likely unnecessary because proteolysis is not a primary mechanism used to process nutrients obtained from the fungus), a loss of genes involved in arginine biosynthesis (suggesting that this amino acid is obtained from the fungus), and the absence of a hexamerin (which sequesters amino acids during larval development in other insects). Following recent reports of genome sequences from other insects that engage in symbioses with beneficial microbes, the A. cephalotes genome provides new insights into the symbiotic lifestyle of this ant and advances our understanding of host-microbe symbioses. © 2011 Suen et al. Source

Anderson T.L.,University of Missouri | Anderson T.L.,Murray State University | Mott C.L.,Valdosta State University | Levine T.D.,Murray State University | And 2 more authors.

Predation risk is an important contributor to community structure that varies in response to abiotic and biotic factors In aquatic habitats, predation risk is often linked to hydroperiod as the latter directly influences predator identity within these ecosystems For pond-breeding salamanders, intraguild predation (IGP) and cannibalism are prevalent interactions in larval communities, but the frequency of each type of agonistic interaction, as well as changes in their pervasiveness along hydroperiod gradients are not well understood Size-structured populations of aquatic life stages (paedomorphic adults and overwintered larvae) of mole salamanders (Ambystoma talpoideum) have the potential to be dominant IG predators and cannibals in permanent ponds because of large size advantages over successive cohorts, but the species exists as only a single larval cohort in temporary ponds with reduced predatory abilities on guild members Thus, both the potential for and intensity of predation by this species is linked to hydroperiod; yet, the predatory abilities of aquatic life stages of mole salamanders have not been evaluated This study examined the extent to which larger size classes (paedomorphs and overwintered larvae) of mole salamanders preyed upon conspecifics and a congeneric competitor, the spotted salamander (Ambystoma maculatum) Predation trials occurred in indoor microcosms and were executed under two habitat treatments that included pseudo-natural conditions containing alternate prey and refugia, as well as simplified environments (no alternative food or cover) Embryos or hatchlings of mole and spotted salamanders were exposed either separately or concurrently to paedomorphic and overwintered larval mole salamanders in each habitat treatment Additionally, overwintered larvae were offered as prey to paedomorphic adults No significant differences in mortality were observed between habitat treatments (complex versus simple) for either embryo or hatchling predation experiments Mortality of mole and spotted embryos did not differ when they were offered separately or together, but paedomorphs caused significantly higher mortality among mole embryos compared to spotted embryos Hatchlings of both species were heavily preyed upon (nearly 100% in all trials), but overwintered larvae exhibited 100% survival with paedomorph predators, indicating size-thresholds of predation risk that were not species specific Paedomorphs and overwintered larvae therefore are most likely generalist predators that feed equally and effectively on hatchlings of co-occurring species, but are more likely to consume egg masses that do not incur significant handling costs When present, paedomorphs or overwintered larvae have the potential to alter population dynamics of both guild members and conspecifics by being dominant predators on early life stages As the prevalence of overwintering and paedomorphosis varies along hydroperiod gradients, predation risk from this species is likely to occur discontinuously and thereby may be an important, yet variable, structuring force © 2013 by the American Society of Ichthyologists and Herpetologists. Source

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