Factors Affecting the Predator-Prey Relationship Between Predaceous Diving Beetle Larvae (Dytiscus fasciventris) and Two Anuran Tadpole Species (Bufo americanus and Hyla crucifer)

It has previously been demonstrated that American toad (Bufo americanus) tadpoles are more vulnerable to predation by diving beetle larvae (Dytiscus fasciventris) than are spring peeper (Hyla crucifer) tadpoles. A laboratory study was undertaken to further delineate factors that contribute to the differential vulnerability observed. Beetle larvae are more effective tadpole predators in shallow, than in deep, water and appear to prefer to adopt a sit-and-wait predator strategy while clinging to emergent vegetation. Depth preference experiments in the laboratory indicated that both tadpole species prefer deep areas to shallow areas irrespective of whether a predator was present or absent. Dytiscus preferred the shallow end (0 - 5 cm of water) of the depth choice tank when tadpoles were absent, but preferred deeper areas when tadpoles were present. Beetle larvae prefer to eat in shallow areas, or on vegetation near the water surface. Both tadpole species appear to be more vulnerable to predation on light colored substrates, indicating that vision may be a more important prey locating mechanism in beetle larvae than previously thought. Bufo tadpoles move significantly more than Hyla tadpoles, which results in a higher vulnerability for Bufo. Field experiments show a positive relationship between tadpole density and the number of tadpoles a beetle larva is able to capture. Field results also suggest that late stage Bufo tadpoles (which move the same amount Hyla tadpoles do) are not more vulnerable to beetle larvae than are Hyla tadpoles, further delineating the relationship between the amount of movement tadpoles exhibit and the level of tadpole vulnerability to beetle larvae. These results are discussed with reference to some evolutionary theories of predator-prey systems

Analyses of the Effects of an Exotic Lizard (\u3cem\u3eAnolis sagrei\u3c/em\u3e) on a Native Lizard (\u3cem\u3eAnolis carolinensis\u3c/em\u3e) in Florida, Using Islands as Experimental Units

The green anole, Anolis carolinensis (Sauria: Polychrotidae), North America\u27s only native anole, was abundant in even the most disturbed urban environs of Florida until recently. The Cuban brown anole, A. sagrei, was introduced to six Florida ports in the 1940s. Since then, it has become the most abundant lizard in peninsular Florida, has spread into Georgia and two other southeastern states, and has been blamed for the decline of A. carolinensis. Because A. carolinensis declines soon after the arrival of A. sagrei, it has been difficult to identify the mechanisms involved. I studied the effect of A. sagrei on A. carolinensis on dredge-spoil islands along the east coast of Florida. By introducing small numbers of A. sagrei to two very different islands, I contrasted their colonizing abilities, densities, and body conditions in two different habitat types. Stomach content analyses of the two species in sympatry indicated that they consume very similar proportions and taxa of arthropods, and that they consume each other\u27s hatchlings in natural situations. In 1995, I introduced A. sagrei onto three islands occupied by A. carolinensis, and used three islands containing native A. carolinensis as controls. Over four summers, I monitored populations using capture-mark-recapture techniques, and collected body, microhabitat, and spatial data. Green anole densities and habitat parameters were similar over time on the controls. On the treatment islands, A. sagrei became dense in all habitat types, A. carolinensis declined as A. sagrei expanded, and survivors shifted their perch heights and utilized different habitats than they did prior to the introductions of A. sagrei. The decline was due to a lack of recruitment in subsequent years, suggesting that asymmetric intra-guild predation was involved in the rapid decline of green anoles. Sympatric green anole populations remained viable only in habitat patches containing dense understory vegetation, which may have provided more food and ameliorated the effects of hatchling predation Green anoles might remain viable in urban or disturbed environs where A. sagrei attains very high densities, as long as sufficient understory vegetation is present to ensure successful recruitment of hatchling green anoles to adulthood

What do community-dwelling Caucasian and South Asian 60–70 year olds think about exercise for fall prevention?

Background: strategies to prevent falls often recommend regular exercise. However, 40% of over 50s in the UK report less physical activity than is recommended. Even higher rates of sedentary behaviour have been reported among South Asian older adults

Character Displacement in the Midst of Substantial Background Evolution in Anolis Lizard Island Populations

Negative interactions between species can generate divergent selection that causes character displacement. However, other processes cause similar divergence. We use spatial and temporal replication across island populations of Anolis lizards to assess the importance of negative interactions in driving trait shifts. Previous work showed that the establishment of Anolis sagrei on islands drove resident Anolis carolinensis to perch higher and evolve larger toepads. To further test the interaction\u27s causality and predictability, we resurveyed a subset of islands nine years later. Anolis sagrei had established on one island between surveys. We found that A. carolinensis on this island now perch higher and have larger toepads. However, toepad morphology change on this island was not distinct from shifts on six other islands whose Anolis community composition had not changed. Thus, the presence of A. sagrei only partly explains A. carolinensis trait variation across space and time. We also found that A. carolinensis on islands with previously established A. sagrei now perch higher than a decade ago, and that current A. carolinensis perch height is correlated with A. sagrei density. Our results suggest that character displacement likely interacts with other evolutionary processes in this system, and that temporal data are key to detecting such interactions

A putative relay circuit providing low-threshold mechanoreceptive input to lamina I projection neurons via vertical cells in lamina II of the rat dorsal horn

Background: Lamina I projection neurons respond to painful stimuli, and some are also activated by touch or hair movement. Neuropathic pain resulting from peripheral nerve damage is often associated with tactile allodynia (touch-evoked pain), and this may result from increased responsiveness of lamina I projection neurons to non-noxious mechanical stimuli. It is thought that polysynaptic pathways involving excitatory interneurons can transmit tactile inputs to lamina I projection neurons, but that these are normally suppressed by inhibitory interneurons. Vertical cells in lamina II provide a potential route through which tactile stimuli can activate lamina I projection neurons, since their dendrites extend into the region where tactile afferents terminate, while their axons can innervate the projection cells. The aim of this study was to determine whether vertical cell dendrites were contacted by the central terminals of low-threshold mechanoreceptive primary afferents. Results: We initially demonstrated contacts between dendritic spines of vertical cells that had been recorded in spinal cord slices and axonal boutons containing the vesicular glutamate transporter 1 (VGLUT1), which is expressed by myelinated low-threshold mechanoreceptive afferents. To confirm that the VGLUT1 boutons included primary afferents, we then examined vertical cells recorded in rats that had received injections of cholera toxin B subunit (CTb) into the sciatic nerve. We found that over half of the VGLUT1 boutons contacting the vertical cells were CTb-immunoreactive, indicating that they were of primary afferent origin. Conclusions: These results show that vertical cell dendritic spines are frequently contacted by the central terminals of myelinated low-threshold mechanoreceptive afferents. Since dendritic spines are associated with excitatory synapses, it is likely that most of these contacts were synaptic. Vertical cells in lamina II are therefore a potential route through which tactile afferents can activate lamina I projection neurons, and this pathway could play a role in tactile allodynia

Conserved presence of G-quadruplex forming sequences in the Long Terminal Repeat Promoter of Lentiviruses

G-quadruplexes (G4s) are secondary structures of nucleic acids that epigenetically regulate cellular processes. In the human immunodeficiency lentivirus 1 (HIV-1), dynamic G4s are located in the unique viral LTR promoter. Folding of HIV-1 LTR G4s inhibits viral transcription; stabilization by G4 ligands intensifies this effect. Cellular proteins modulate viral transcription by inducing/unfolding LTR G4s. We here expanded our investigation on the presence of LTR G4s to all lentiviruses. G4s in the 5'-LTR U3 region were completely conserved in primate lentiviruses. A G4 was also present in a cattle-infecting lentivirus. All other non-primate lentiviruses displayed hints of less stable G4s. In primate lentiviruses, the possibility to fold into G4s was highly conserved among strains. LTR G4 sequences were very similar among phylogenetically related primate viruses, while they increasingly differed in viruses that diverged early from a common ancestor. A strong correlation between primate lentivirus LTR G4s and Sp1/NF\u3baB binding sites was found. All LTR G4s folded: their complexity was assessed by polymerase stop assay. Our data support a role of the lentiviruses 5'-LTR G4 region as control centre of viral transcription, where folding/unfolding of G4s and multiple recruitment of factors based on both sequence and structure may take place