The “ricochet effect” and prey capture in colonial spiders

Summary Increased prey capture efficiency in colonial spiders is a consequence of the ricochet effect, as prey are captured after they bounce off several webs in succession. In this study, the prey capture of three species of colonial spiders in the genus Metepeira from Mexico are compared. These species, from different habitats, show varying levels of social organization (group size and withingroup spacing) that affect prey capture from ricochets. Metepeira sp. a (a presumed new species tentatively named atascadero) from desert grassland habitats, occur solitarily or in small groups, and gain little from prey ricochets: prey capture rates are low and variance in prey captured/spider is high. M. spinipes, from mesic agricultural sites, occur in groups of 10–150, and show a ricochet effect resulting in more and larger prey, and reduced variance in capture rate. M. incrassata, from tropical rainforest/agricultural sites, occur in large colonies of hundreds to thousands of individuals, and show a similar ricochet effect. The ricochet effect does not influence taxonomic composition of prey in either M. atascadero or M. spinipes, but does in tropical M. incrassata. This result, however, is primarily due to the capacity of certain taxa (eg., Lepidoptera), more common in the tropics, to escape more easily from spider webs. A comparison of prey capture efficiency of colonial M. incrassata with that of solitary M. atascadero shows that the ricochet effect provides an increase in efficiency across all size classes of prey.     

Direct observation of α-actinin tension and recruitment at focal adhesions during contact growth

Adherent cells interact with extracellular matrix via cell–substrate contacts at focal adhesions. The dynamic assembly and disassembly of focal adhesions enables cell attachment, migration and growth. While the influence of mechanical forces on the formation and growth of focal adhesions has been widely observed, the force loading on specific proteins at focal adhesion complex is not clear. By co-expressing force sensitive α-actinin FRET probes and fluorescence labeled paxillin in MDCK cells, we have simultaneously observed the time-dependent changes in tension in α-actinin and the dynamics of focal adhesion during cell migration. We show that increase in tension in α-actinin at the focal adhesion coincides with elongation of the adhesion in its growth phase. The enlargement of focal adhesion is through a force sensitive recruitment of α-actinin and paxillin to the adhesion sites. Changes in α-actinin tension and correlated relocation of α-actinin in an active adhesion also guide the growth direction of the adhesion. The results support the model that cytoskeletal tension is coupled to focal adhesion via the linking protein, α-actinin at the adhesion complex. Lysophosphatidic acid caused an immediate increase in α-actinin tension followed by drastic focal adhesion formation and elongation. Application of Rho-ROCK inhibitor, Y27632, resulted in reversible reduction in tension in α-actinin and disassociation of focal adhesion, suggesting the involvement of myosin-II mediated contractile force in the focal adhesion dynamics. These findings suggest that α-actinin not only serves as a physical linker between cytoskeleton and integrin, but also participates in force transmission at adhesion sites to facilitate adhesion?s growth.     

Optimal (‘Wiener’) digital filtering of auditory evoked potentials: use of coherence estimates

Auditory evoked potentials (AEPs) to 40 Hz clicks and amplitude-modulated 500 Hz tones in human subjects were digitally filtered using an optimal (‘Wiener’) filter uniquely determined for each AEP. Use of coherence functions to compute coefficients appropriate for filtering grand average AEPs or subsets such as split-half averages is described. Wiener-filtered AEPs correlated better than unfiltered AEPs with split-half replicates and with references AEPs (obtained with long data collection periods). Visual detection thresholds were lower (more sensitive) for the Wiener-filtered AEPs, but not as low as objectively determined thresholds using coherence values.     

'Home' choice and modification by juvenile Octopus vulgaris (Mollusca: Cephalopoda): specialized intelligence and tool use?

Analysis of 'homes' occupied by juvenile Octopus vulgaris shows flexible behaviour which may indicate specialized intelligence and tool use. Octopuses occupied sheltered areas for a short time, average 10 days, but stayed longer in larger homes and in areas where preferred prey was available. They did not simply respond to perceptual characteristics of a site, but instead chose locations potentially suitable and modified them by removing rocks and sand and bringing in items partially to block the aperture.     

Are irrigation and grazing effects transferred,accumulated, or counteracted during plant recruitment?

How do effects from perturbations such as irrigation and grazing that have an impact at one stage of the recruitment process (e.g., seedling) affect performance at later stages (e.g., adult)? Such effects may be transferred to later stages without any further change (transferred effects), reinforced by a similar effect so that their importance increases (accumulative effect), or counteracted at later stages by an opposite effect (counteractive effect). We analysed the predominance of transferred, accumulative, and counteractive effects depending on (1) organization level (community, functional group, and species levels), (2) life cycle stage (seeds, seedlings, and adults), (3) grass/forb functional group (forbs versus grasses), and (4) seed mass (small-seeded species, medium-seeded species, and large-seeded species). The study was conducted in Alcalá de Henares, central Spain. During one annual cycle, we counted the number of readily germinable seeds (3,909 seeds: 2,156 forbs and 1,753 grasses), emerged seedlings (2,126 seedlings: 1,238 forbs and 888 grasses), and surviving seedlings up to reproductive adult status (917 adults: 217 forbs and 700 grasses) of all species (74 species) in a factorial field experiment under three different simulated rainfall and three seasonal sheep grazing regimes in a natural Mediterranean annual plant community composed of forbs (dicotyledonous herbs) and grasses (monocotyledonous herbs). Our main results were: (1) the proportion of transferred and counteractive effects was similar between the three studied organization levels (community, functional group, and species levels); (2) we detected many more counteractive effects in the seedling stage than in the adult stage; (3) we did not find more counteractive effects in forbs versus grasses, but transferred effects were more frequent in grasses; and (4) we found more counteractive effects with decreasing seed mass and more transferred effects with increasing seed mass. Our main conclusions were that the prevalence of counteractive effects reduces the sensitivity of the whole recruitment process and enhances the relative importance of the final stage (adults). The prevalence of transferred effects makes the recruitment process more predictable and more dependent on the early stages (seeds and seedlings).     

Dynamics of births and juvenile recruitment in Mara–Serengeti ungulates in relation to climatic and land use changes

Natality and recruitment govern animal population dynamics, but their responses to fluctuating resources, competition, predation, shifting habitat conditions, density feedback and diseases are poorly understood. To understand the influences of climatic and land use changes on population dynamics, we monitored monthly changes in births and juvenile recruitment in seven ungulate species for 15 years (1989–2003) in the Masai Mara Reserve of Kenya. Recruitment rates declined for all species but giraffe, likely due to habitat alteration and increasing vulnerability of animals associated with recurrent severe droughts, rising temperatures, unprecedentedly strong and prolonged El Niño-Southern Oscillation (ENSO) episodes, expansion of settlements, cultivation and human population growth in pastoral ranches adjoining the reserve. Birth rate showed strong and humped relationships with moving averages of monthly rainfall, whereas recruitment responded strongly to cumulative past rainfall. Increasing livestock incursions into the reserve depressed recruitment rate for quarter-grown topi. Expansion of pastoral settlements depressed birth rate in impala, zebra and giraffe. Frequent ENSO-related droughts caused progressive habitat desiccation and hence nutritional shortfalls for ungulates. The responses to climatic, land use and resource influences did not reflect body size, migratory or resident lifestyle, dietary guild, digestive physiology or degree of synchrony of breeding of the ungulate species.     

IL-17 and TNF-α sustain neutrophil recruitment during inflammation through synergistic effects on endothelial activation

IL-17A (IL-17) is the signature cytokine produced by Th17 cells and has been implicated in host defense against infection and the pathophysiology of autoimmunity and cardiovascular disease. Little is known, however, about the influence of IL-17 on endothelial activation and leukocyte influx to sites of inflammation. We hypothesized that IL-17 would induce a distinct pattern of endothelial activation and leukocyte recruitment when compared with the Th1 cytokine IFN-γ. We found that IL-17 alone had minimal activating effects on cultured endothelium, whereas the combination of TNF-α and IL-17 produced a synergistic increase in the expression of both P-selectin and E-selectin. Using intravital microscopy of the mouse cremaster muscle, we found that TNF-α and IL-17 also led to a synergistic increase in E-selectin-dependent leukocyte rolling on microvascular endothelium in vivo. In addition, TNF-α and IL-17 enhanced endothelial expression of the neutrophilic chemokines CXCL1, CXCL2, and CXCL5 and led to a functional increase in leukocyte transmigration in vivo and CXCR2-dependent neutrophil but not T cell transmigration in a parallel-plate flow chamber system. By contrast, endothelial activation with TNF-α and IFN-γ preferentially induced the expression of the integrin ligands ICAM-1 and VCAM-1, as well as the T cell chemokines CXCL9, CXCL10, and CCL5. These effects were further associated with a functional increase in T cell but not neutrophil transmigration under laminar shear flow. Overall, these data show that IL-17 and TNF-α act in a synergistic manner to induce a distinct pattern of endothelial activation that sustains and enhances neutrophil influx to sites of inflammation.     

Maternal Smoking during Pregnancy and Daughters’ Preeclampsia Risk

Background

An obstetrical paradox is that maternal smoking is protective for the development of preeclampsia. However, there are no prior studies investigating the risk of preeclampsia in women who were exposed to tobacco smoking during their own fetal period. We aimed to study the subsequent risk of preeclampsia in women who were exposed to tobacco smoke in utero, using a national population-based register.

Methods

Data were obtained from the Medical Birth Register of Sweden for women who were born in 1982 (smoking data first recorded) or after, who had given birth to at least one child; 153 885 pregnancies were included.

Results

The associations between intrauterine smoking exposure (three categories: non-smokers, 1–9 cigarettes/day [moderate exposure], and >9 cigarettes/day [heavy exposure]) and subsequent preeclampsia (n = 5721) were assessed using logistic regressions. In models adjusted for maternal age, parity and own smoking, the odds ratios (OR) for preeclampsia were 1.06 [95% CI: 0.99,1.13 for moderate intrauterine exposure, and 1.18, [95% CI: 1.10,1.27] for heavy exposure. Estimates were slightly strengthened in non-smoking women who experienced heavy intrauterine exposure (adjusted OR 1.24 [95% CI: 1.14,1.34]). Results were no longer statistically significant after adjustment for the woman’s own BMI, gestational age and birthweight Z-scores.

Conclusion

These data revealed some evidence of a possible weak positive association between intrauterine smoking exposure and the risk of subsequent preeclampsia, however, results were not significant over all manifestations of preeclampsia and confounder adjustment. The increased risk might be mediated through exposed women’s own BMI or birthweight.     

The use and Development of America’s Forest Resources

The “supply-demand” situation for wood in the United States is reviewed. In the immediate future, no shortage of wood is expected, but there is some disagreement about whether or not we will face shortages by the year 2000. The concept of multiple use and the element of time in the production function further complicate an already complicated planning problem. Increased ability to (1) modify site (use of fertilizers, insect, disease, and fire control), (2) develop improved trees, (3) use mechanized equipment, and (4) develop better information and analytical methods as aids in decision making will mean a continuing shift away from our previous ideas about wood as a wild resource.     

Sensory evoked and event related oscillations in Alzheimer’s disease: a short review

Diagnosis and treatment of Alzheimer’s disease (AD) depend on clinical evaluation and there is a strong need for an objective tool as a biomarker. Our group has investigated brain oscillatory responses in a small group of AD subjects. We found that the de novo (untreated) AD group differs from both the cholinergically-treated AD group and aged-matched healthy controls in theta and delta responses over left frontal-central areas after cognitive stimulation. On the contrary, the difference observed in AD groups upon a sensory visual stimulation includes response increase over primary or secondary visual sensorial areas compared to controls. These findings imply at least two different neural networks, depending on type of stimulation (i.e. cognitive or sensory). The default mode defined as activity in resting state in AD seems to be affected electrophysiologically. Coherences are also very valuable in observing the group differences, especially when a cognitive stimulus is applied. In healthy controls, higher coherence values are elicited after a cognitive stimulus than after a sensory task. Our findings support the notion of disconnectivity of cortico-cortical connections in AD. The differences in comparison of oscillatory responses upon sensory and cognitive stimulations and their role as a biomarker in AD await further investigation in series with a greater number of subjects.     

Wild Wunderpus photogenicus and Octopus cyanea employ asphyxiating ‘constricting’ in interactions with other octopuses

Aggressive constricting including asphyxiation was observed in wild octopuses (Octopus cyanea Gray, 1849, and Wunderpus photogenicus Hochberg, Norman & Finn, 2006 Hochberg, F.G., Norman, M.D. & Finn, J. (2006) Wunderpus photogenicus n. gen. and sp., a new Octopus from the shallow waters of the Indo-Malayan Archipelago (Cephalopoda: Octopodidae). Molluscan Research 26, 128–140.[Web of Science ®] , [Google Scholar]). The distal portion of a dorsolateral arm formed a loop around the mantle of another octopus, in at least one case preventing the flow of water into the mantle, over the gills and out of the funnel. Constricting also may have prevented the subordinate individual from releasing ink, a possible irritant and predator attractant. A female O. cyanea used constricting as a form of fatal aggression to asphyxiate a male as part of apparent sexual cannibalism. This female killed a male with which she was mating using the ‘distance’ position. Constriction allowed a W. photogenicus to win during physical interspecific aggression with a close relative, Thaumoctopus mimicus Norman & Hochberg, 2005 Norman, M.D. & Hochberg, F.G. (2005) The ‘Mimic Octopus’ (Thaumoctopus mimicus n. gen. et. sp.), a new octopus from the tropical Indo-West Pacific (Cephalopoda: Octopodidae). Molluscan Research 25, 57–70. [Google Scholar]. This action took place near an immediately available food source and interrupted foraging by T. mimicus, providing possible evidence of interference competition among closely related sympatric cephalopod species in the wild.     

The complete mitochondrial genomes of two octopods of the eastern Pacific Ocean: Octopus mimus and ‘Octopus’ fitchi (Cephalopoda: Octopodidae) and their phylogenetic position within Octopoda

Molecular Biology Reports - The complete mitochondrial genomes of two important octopus species from the eastern Pacific were sequenced, obtaining their complete nucleotide sequences. Octopus mimus...     

Wild Goffin’s cockatoos flexibly manufacture and use tool sets

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Influence of vibration on the excitability of spinal α-motoneurons under static conditions and during evoked stepping in humans

The excitability of spinal α-motoneurons in healthy humans was investigated with vibrostimulation (20–60 Hz) applied to different groups of muscles both under stationary conditions and during vibration-evoked stepping movements with leg suspension. In 15 subjects, the H-reflex amplitude was compared under the conditions of vibration of the left leg quadriceps femoris (QFM) or biceps femoris (BFM) muscle, as well as under the conditions of vibration of the contralateral, motionless leg QFM muscle in three spatial positions of the body: upright, supine, and lying on the side with the left leg suspended. Under dynamic conditions, the H-reflex value was compared during evoked and voluntary steppings at eight intervals of the step cycle. In all body positions, the vibration of each ipsilateral leg muscle caused a significant H-reflex suppression, this suppression being more prominent under the air-stepping conditions. The vibration of the contralateral leg QFM had weak influence on the H-reflex amplitude. In seven subjects, the vibration of the ipsilateral and contralateral leg muscles generated stepping movements. During vibration-evoked air-stepping, the H-reflex had different amplitudes in different phases of the step cycle. At the same time, the differences between responses under voluntary and involuntary stepping conditions were revealed only in the step cycle phase corresponding to the stance phase. Thus, the different degrees of the H-reflex suppression by vibration in different spatial positions of the body seem to depend on the summary afferent inflows to the spinal cord interneurons involved in the regulation of locomotion and posture. Apparently, an increase in the spinal cord neuronal excitability, which is necessary for activating locomotor automatism under the leg unloading conditions, occurs during evoked air-stepping in the swing phase.     

Children’s and Adults’ On-Line Processing of Syntactically Ambiguous Sentences during Reading

While there has been a fair amount of research investigating children’s syntactic processing during spoken language comprehension, and a wealth of research examining adults’ syntactic processing during reading, as yet very little research has focused on syntactic processing during text reading in children. In two experiments, children and adults read sentences containing a temporary syntactic ambiguity while their eye movements were monitored. In Experiment 1, participants read sentences such as, ‘The boy poked the elephant with the long stick/trunk from outside the cage’ in which the attachment of a prepositional phrase was manipulated. In Experiment 2, participants read sentences such as, ‘I think I’ll wear the new skirt I bought tomorrow/yesterday. It’s really nice’ in which the attachment of an adverbial phrase was manipulated. Results showed that adults and children exhibited similar processing preferences, but that children were delayed relative to adults in their detection of initial syntactic misanalysis. It is concluded that children and adults have the same sentence-parsing mechanism in place, but that it operates with a slightly different time course. In addition, the data support the hypothesis that the visual processing system develops at a different rate than the linguistic processing system in children.     

V˙O2peak and the gas-exchange anaerobic threshold during incremental arm cranking in able-bodied and paraplegic men

Resting energy expenditure, peak oxygen uptake (VO2peak) and the gas-exchange anaerobic threshold (Than) were measured during incremental arm cranking (15 W x min(-1)) in six able-bodied (AB) and six paraplegic (P) subjects. Only male subjects with traumatic spinal cord injuries in the area of the 10-12th thoracic segment were included in the P group. All AB and P subjects were physically active. Mean (SE) values for age and body mass were 28 (2) years and 78.9 (3.9) kg for the AB group and 32 (4) years and 70.8 (7.9) kg for the P group (P>0.05). Resting energy expenditure values were not found to be significantly different between AB [5.8 (0.2) kJ x min(-1)] and P [5.1 (0.3) kJ min(-1)] subjects. Mean VO2peak values were 29.3 (2.4) ml x kg(-1) min(-1) and 29.6 (2.2) ml x kg(-1) x min(-1) for the AB and P groups, respectively (P>0.05). Absolute oxygen uptake values measured at two gas-exchange anaerobic threshold (Than) were not significantly different between the two groups. However, the Than occurred at a significantly higher percentage of VO2peak in the P [58.9 (1.7)%] group than in the AB [50.0 (2.8)%] group (P<0.05). Moreover, respiratory exchange ratio (R) values obtained at the Than and at 15, 45, 60, 75 and 90 W of incremental exercise were significantly lower in the P group than in the AB group. Heart rates were significantly elevated at every submaximal work stage (15-120 W) in the P group compared to the AB group (P<0.05). These findings suggest that chronic daily wheelchair activity produces local adaptations in the functional upper-body musculature, which reduce glycogenolysis and increase the rate of lipid utilization (lower R) during arm exercise. These local adaptations may be in part responsible for the significantly higher Than observed for arm exercise in P subjects, even though VO2peak values were essentially the same for both groups.