Correlation of metal decoration and topochemistry on protein surfaces

On the surface of protein molecules the formation of metal clusters during vacuum condensation is controlled by topochemical features of the substrate and by specific properties of the decorating material. The resulting metal distribution (decoration pattern) can be mapped by electron microscopy in conjunction with image processing. We have applied this technique to freeze-etched crystals of the lumazine synthase-riboflavin synthase complex and its derivative obtained by binding of the heteropolytungstate (NaP5W30O110)(NH4)14.31 H2O. The decoration pattern of the free protein and its heteropolytungstate derivative showed marked differences. The correlation of these data with the X-ray structure of the protein showed an increased affinity of both gold and silver to the location of heteropolytungstate. Decoration sites can, but do not need to, be close to the protein surface. Actually, two of the observed decoration sites are located on a layer of ice as thick as 20 A, which apparently transmits underlying topochemical features. Preferential affinity of a site to a given metal must be seen as a property that depends on specific interaction with the decorating material but also on the differential affinities in adjacent areas.     

Non-heritable change of a spirochaete's phenotype by decoration of the cell surface with exogenous lipoproteins

Genetic transformation of Borrelia spp. is limited in development and has found application in only one species. For a non-genetic approach for manipulating the phenotype of these spirochaetes, we determined whether exogenous recombinant lipoproteins would incorporate in the cell's outer membrane. Using unlabelled or 125I-labelled Osp proteins, Osp-specific monoclonal antibodies, proteinase K and formaldehyde as reagents, we found that decoration of spirochaetes had the following characteristics. (i) Purified recombinant OspA or OspD lipoproteins associated with Borrelia burgdorferi and B. hermsii cells that lacked abundant lipoproteins of their own. (ii) This decoration of the cells with exogenous OspA did not affect cell's viability. (iii) The decoration was concentration and temperature dependent and stable for at least 24 h. (iv) Like native OspA, the recombinant OspA decorating the cells was accessible to antibodies and proteases and could be cross-linked to the integral outer membrane protein, P66. (v) Decoration of viable B. burgdorferi and B. hermsii with OspA rendered the cells susceptible to killing by OspA-specific antiserum. Such non-genetic alteration of the surface of a bacterium may be used to study functions and properties of lipoproteins in situ.     

Tube decoration may not be cryptic for Diopatra cuprea (Polychaeta: Onuphidae)

Previous studies have suggested several adaptive functions for the decorated tube caps of Diopatra cuprea (Polychaeta: Onuphidae). We experimentally tested the hypothesis that decoration provides crypsis. A series of field experiments quantified predation-related damage done to tube caps that were (1) devoid of decoration, (2) decorated with algae, or (3) decorated with shell fragments. If decoration provides crypsis, then undecorated tube caps should experience more damage than decorated tube caps; this pattern was not observed. Decoration may still reduce predation rates by means other than crypsis, but these results strongly suggest that tube decoration does not interfere with predator recognition of D. cuprea tube caps and that crypsis is consequently not important in this system.     

Evaluating reproductive fitness and metabolic costs for insecticide resistance in Myzus persicae from Chile

The development of insecticide resistance in pest insects is an increasing problem for agriculture, forestry and public health. Aphids are ubiquitous herbivorous insects, with approximately 4700 known species, of which less than 5% exploit the agricultural environment successfully. Of these, the peach‐potato aphid Myzus persicae Sulzer is recognized as one of the most important pests worldwide because it has acquired resistance to many insecticides. Although resistance to insecticides provides important benefits for pests in agricultural fields that are treated with insecticides, it may be associated with fitness (or other) costs in environments that are insecticide free. In the present study, the fitness and energy costs that might be experienced by M. persicae in an insecticide‐free environment when carrying at least one insecticide resistance mutation (IRM), or by having an increased production of esterases, are evaluated. The study investigates whether genotypes that have an IRM also have enhanced esterase production, whether there is any metabolic cost associated with insecticide resistance, and whether there are any fitness costs associated with insecticide resistance and metabolic expenditure. The intrinsic rate of increase, standard metabolic rate (i.e. a measure of maintenance costs) and constitutive esterase activity are determined for 30 different multilocus genotypes carrying (or not carrying) at least one of the two most frequent insecticide resistance mutations (MACE and kdr/super‐kdr) that occur in Chile. The results show that genotypes carrying at least one IRM have higher levels of total esterase activity than genotypes without an IRM, that there is no evidence of an energy cost associated with total esterase activity or IRM, and no evidence for a reproductive fitness cost associated with total esterase activity, IRM or metabolic rate. The results agree with previous studies showing linkage disequilibrium between insecticide resistance mechanisms, although they contrast with those of studies that report fitness costs associated with insecticide resistance in Myzus persicae.     

Alternative camouflage strategies mediate predation risk among closely related co-occurring kelp crabs

Although camouflage is a common predator defense strategy across a wide variety of organisms, direct tests of the adaptive and ecological consequences of camouflage are rare. In this study, we demonstrated that closely related crabs in the family Epialtidae coexist in the same algal environment but use alternative forms of camouflage––decoration and color change––to protect themselves from predation. Decoration and color change are both plastic camouflage strategies in that they can be changed to match different habitats: decoration occurs on a short timescale (hours to days), while color change accompanies molting and occurs on longer timescales (months). We found that the species that decorated the most had the lowest magnitude of color change (Pugettia richii); the species that decorated the least showed the highest magnitude of color change (Pugettia producta), and a third species (Mimulus foliatus) was intermediate in both decoration and color change, suggesting a negative correlation in utilization of these strategies. This negative correlation between color change and decoration camouflage utilization mirrored the effectiveness of these camouflage strategies in reducing predation in different species. Color camouflage primarily reduced predation on P. producta, while decoration camouflage (but not color camouflage) reduced predation on P. richii. These results indicate there might be among-species trade-offs in utilization and/or effectiveness of these two forms of plastic camouflage, with important consequences for distribution of these species among habitats and the evolution of different camouflage strategies in this group.     

Effects of chemical modification, tropomyosin, and myosin subfragment 1 on the yield strength and critical concentration of F-actin

The effects of coupling with tetramethylrhodamine-5-iodoacetamide and of the decoration with tropomyosin and with myosin subfragment 1 on the elastic properties of F-actin filament are investigated. At 22 degrees C, in 15 mM orthophosphate and 3 mM MgCl2, tetramethylrhodamine F-actin displays a yield strength of 3.69 +/- 0.213 pN and an elastic modulus by stretching of 0.91 MPa. Decoration with tropomyosin increases the yield strength of tetramethylrhodamine F-actin to 10.51 +/- 0.24 pN and the elastic modulus by stretching to 23-75 MPa. Mixtures of myosin subfragment 1 and tetramethylrhodamine F-actin at the 0.2:1, 0.4:1, 0.6:1, 0.8:1, and 1:1 molar ratios are also studied. Both yield strength and the elastic modulus by stretching are found to increase progressively with the ratio. At the 1:1 molar ratio, the yield strength is 15.81 +/- 0.26 pN and the elastic modulus by stretching is 13.45 to 40 MPa. Decoration of tetramethylrhodamine F-actin with both tropomyosin and myosin subfragment 1, at the 1:1 molar ratio with the actin monomer, produces filaments with an yield strength of 22.3 +/- 0.48 pN.     

'IntraCell' plugin for assessment of intracellular localization of nano-delivery systems and their targeting to the individual organelles

Efficient intracellular targeting of drugs and drug delivery systems (DDSs) is a major challenge that should be overcome to enhance the therapeutic efficiency of biopharmaceuticals and other intracellularly-acting drugs. Studies that quantitatively assess the mechanisms, barriers, and efficiency of intracellular drug delivery are required to determine the therapeutic potential of intracellular targeting of nano-delivery systems. In this study we report development and application of a novel ‘IntraCell’ plugin for ImageJ that is useful for quantitative assessment of uptake and intracellular localization of the drug/DDS and estimation of targeting efficiency. The developed plugin is based on threshold-based identification of borders of cell and of the individual organelles on confocal images and pixel-by-pixel analysis of fluorescence intensities.We applied the developed ‘IntraCell’ plugin to investigate uptake and intracellular targeting of novel endoplasmic reticulum (ER)-targeted delivery system based on PLGA nanoparticles decorated with ER-targeting or control peptides and encapsulating antigenic peptide and fluorescent marker. Decoration of the nanoparticles with peptidic residues affected their uptake and intracellular trafficking in HeLa cells, indicating that the targeting peptide was identified as ER-targeting signal by the intracellular trafficking mechanisms in HeLa cells and that these mechanisms can handle nano-DDS of the size comparable to some intracellular vesicles (hundreds of nanometers in diameter).We conclude that decoration of nanoparticles with peptidic residues affects their intracellular localization and trafficking and can be potentially used for intracellularly-targeted drug delivery. ‘IntraCell’ plugin is an useful tool for quantitative assessment of efficiency of uptake and intracellular drug targeting. In combination with other experimental approaches, it will be useful for the development of intracellularly-targeted formulations with enhanced and controlled drug pharmacological activities, such as delivery of antigenic peptides for anticancer vaccination and for other applications.     

Investment in defense and cost of predator-induced defense along a resource gradient

An organism’s investment in different traits to reduce predation is determined by the fitness benefit of the defense relative to the fitness costs associated with the allocation of time and resources to the defense. Inherent tradeoffs in time and resource allocation should result in differential investment in defense along a resource gradient, but competing models predict different patterns of investment. There are currently insufficient empirical data on changes in investment in defensive traits or their costs along resource gradients to differentiate between the competing allocation models. In this study, I exposed tadpoles to caged predators along a resource gradient in order to estimate investment in defense and costs of defense by assessing predator-induced plasticity. Induced defenses included increased tail depth, reduced feeding, and reduced swimming activity; costs associated with these defenses were reduced developmental rate, reduced growth, and reduced survival. At low resource availability, these costs predominately resulted in reduced survival, while at high resource availability the costs yielded a reduced developmental rate. Defensive traits responded strongly to predation risk, but did not respond to resource availability (with the exception of feeding activity), whereas traits construed as costs of defenses showed the opposite pattern. Therefore, defensive traits were highly sensitive to predation risk, while traits construed as costs of defense were highly sensitive to resource allocation tradeoffs. This difference in sensitivity between the two groups of traits may explain why the correlation between the expression of defensive traits and the expression of the associated defense costs was weak. Furthermore, my results indicate that genetic linkages and mechanistic integration of multiple defensive traits and their associated costs may constrain time and resource allocation in ways that are not addressed in existing models. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Actin filaments elongate from their membrane-associated ends

In limulus sperm an actin filament bundle 55 mum in length extends from the acrosomal vacuole membrane through a canal in the nucleus and then coils in a regular fashion around the base of the nucleus. The bundle expands systematically from 15 filaments near the acrosomal vacuole to 85 filaments at the basal end. Thin sections of sperm fixed during stages in spermatid maturation reveal that the filament bundle begins to assemble on dense material attached to the acrosomal vacuole membrane. In micrographs fo these early stages in maturation, short bundles are seen extending posteriorly from the dense material. The significance is that these short, developing bundles have about 85 filaments, suggesting that the 85-filament end of the bundle is assembled first. By using filament bundles isolated and incubated in vitro with G actin from muscle, we can determine the end “preferred” for addition of actin monomers during polymerization. The end that would be associated with the acrosomal vacuole membrane, a membrane destined to be continuous with the plasma membrane, is preferred about 10 times over the other, thicker end. Decoration of the newly polymerized portions of the filament bundle with subfragment 1 of myosin reveals that the arrowheads point away from the acrosomal vacuole membrane, as is true of other actin filament bundles attached to membranes. From these observations we conclude that the bundle is nucleated from the dense material associated with the acrosomal vacuole and that monomers are added to the membrane-associated end. As monomers are added at the dense material, the thick first-made end of the filament bundle is pushed down through the nucleus where, upon reaching the base of the nucleus, it coils up. Tapering is brought about by the capping of the peripheral filaments in the bundle.     

The costs of singing in nightingales

The costs of singing in birds are poorly understood. One potential type of cost is a metabolic cost of singing. Previous studies have measured short-term changes in oxygen consumption associated with bouts of vocalizations, with equivocal results. In this study, I used an alternative approach to measuring the metabolic cost of singing, by measuring overnight loss of body mass, in male common nightingales, Luscinia megarhynchos, singing at night at different rates. Nightingales were shown not to forage at night. They reached a higher mass at dusk prior to singing more at night, and lost more mass overnight when dusk mass and overnight song rate were high. These results show that singing at night is associated with increased overnight consumption of body reserves, which represents a significant metabolic cost of singing at night. However, the correlation between dusk mass and overnight song rate makes it impossible to determine whether these costs arise from the energetic costs of the singing itself, or from the metabolic costs of the additional body reserves laid down at dusk on nights when song rate was high. There are also likely to be costs associated with accumulating and carrying these extra body reserves during daylight, as well as other potential costs of singing such as an increased risk of predation. These results are consistent with those models of signalling in biology that predict or assume that honest signals are costly. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

The evolution of phenotypic plasticity in spatially structured environments: implications of intraspecific competition, plasticity costs and environmental characteristics

We model the evolution of reaction norms focusing on three aspects: frequency-dependent selection arising from resource competition, maintenance and production costs of phenotypic plasticity, and three characteristics of environmental heterogeneity (frequency of environments, their intrinsic carrying capacity and the sensitivity to phenotypic maladaptation in these environments). We show that (i) reaction norms evolve so as to trade adaptation for acquiring resources against cost avoidance; (ii) maintenance costs cause reaction norms to better adapt to frequent rather than to infrequent environments, whereas production costs do not; and (iii) evolved reaction norms confer better adaptation to environments with low rather than with high intrinsic carrying capacity. The two previous findings contradict earlier theoretical results and originate from two previously unexplored features that are included in our model. First, production costs of phenotypic plasticity are only incurred when a given phenotype is actually produced. Therefore, they are proportional to the frequency of environments, and these frequencies thus affect the selection pressure to avoid costs just as much as the selection pressure to improve adaptation. This prevents the frequency of environments from affecting the evolving reaction norm. Secondly, our model describes the evolution of plasticity for a phenotype determining an individual's capability to acquire resources, and thus its realized carrying capacity. When individuals are distributed randomly across environments, they cannot avoid experiencing environments with intrinsically low carrying capacity. As selection pressures arising from the need to improve adaptation are stronger under such extreme conditions than under mild ones, better adaptation to environments with low rather than with high intrinsic carrying capacity results.     

Behavioural development of howling monkey twins (Alouatta palliata) in Santa Rosa National Park,Costa Rica

Twins born to a young female howling monkey in Santa Rosa National Park, Costa Rica were observed during the first 96 days of their life. The comparison of their development to that of single infants and the comparison of the behaviour of the mother of the twins to that of mothers of single infants revealed few differences. However, qualitative observations suggests that high costs are associated with maternal care of infant twins. The mother had difficulty carrying both infants and was the only female observed to become sick during the study. Increased costs of lactation were not compensated for by an increase in foraging time. It would seem that howling monkey mothers possess a maternal care system which is capable of providing suitable care to twins. However, the costs on the mother of raising twins is suggested as a factor selecting for a litter size of one.     

Costs of loading associated with mate-carrying in the waterstrider, Aquarius remigis

When one sex carries the other during some phase of courtshipor mating, the associated loading may entail a significant costto the carrier. This paper presents a series of laboratory experimentsdesigned to identify the costs of mate-carrying in Aquariusremigis. Female A. remigis mate repeatedly and carry each matefor several hours. Dead males and lead weights were used tosimulate normal mating and loading associated with mate-carrying,respectively. Females carrying weights equivalent to the weightof an average male showed no detectable reductions in survival,lipid reserves, or foraging success, and maintained themselveson the water surface for more than 10 days without access toresting sites. Weights equivalent to two males were supportedfor 6.1 ± 4.9 days. Thus, female A. remigis appear tobe very well adapted to carrying their mates and are unlikelyto be near their load limits when carrying a single mate. However,females carrying males or equivalent weights suffered a significantreduction in maximum mobility (stride length and speed), andan increased risk of predation by frogs (Rana clamitans). Femalescarrying weights were more susceptible to predation than unburdenedfemales but were less susceptible than females carrying males,suggesting that loading contributes significantly to, but doesnot fully explain, the increased predation risk. This risk probablyresults from both reduced mobility due to loading and greatervisibility (size). Possible influences of the costs of loadingon mating behavior and sexual size dimorphism are discussed.     

The ecology of fear and inverted biomass pyramids

In inverted biomass pyramids (IBPs) prey are outnumbered by their predators when measured by biomass. We investigate how prey should behave in the face of danger from higher predator biomass, and how anti-predator behavior (in the form of vigilance) can, in turn, affect the predator–prey system. In this study, we incorporate anti-predator behaviors into a Lotka–Volterra predator–prey model in the form of fixed and facultative vigilance. Facultative vigilance models behavior as a dynamic foraging game, allowing us to assess optimal behavioral responses in the context of IBPs using a dynamical fitness optimization approach. We model vigilance as a tradeoff between safety and either the prey's maximum growth rate or its carrying capacity. We assess the population dynamics of predators and prey with fear responses, and investigate the role fear plays on trophic structure. We found that the ecology of fear plays an important role in predator–prey systems, impacting trophic structure and the occurrence of IBPs. Fixed vigilance works against IBP structure by always reducing the predator–prey biomass ratio at equilibrium with increasing levels of vigilance. Facultative vigilance can actually promote IBPs, as prey can now adjust their vigilance levels to cope with increased predation and the costs associated with vigilance. This is especially true when the effectiveness of vigilance is low and predators are very lethal. In general, these trends are true whether the costs of vigilance are felt on the prey's maximum growth rate or its carrying capacity. Just as the ecology of fear, when first introduced, was used to explain why top carnivores are rare in terrestrial systems, it can also be used to understand how big fierce predators can be common in IBPs.     

Costly parenting: physiological condition over time and season in males of the giant waterbug Abedus dilatatus

Parental care patterns increase offspring fitness but may drive energetic costs to parents. The costs associated with parental care can change over time, decreasing the condition of parents that experience prolonged parental care. Thus, males can modulate parental effort based in the relative fitness cost/benefit pay‐offs under different stages and environmental conditions. The present study assesses the condition of parental males of Abedus dilatatus Say by measuring their lipid, glycogen and carbohydrate contents. We compare the condition in parental males that have experienced recent and prolonged care and that were also collected in the summer and winter. Waterbug males provide parental care via carrying and ventilating eggs on their back. Winter males are smaller and carry fewer eggs compared with summer males. Males with recent care and carrying more eggs present a more lipid content. However, at the end of care, males carrying more eggs present less lipids than males with smaller egg‐pads. Additionally, we find that males collected in the summer present more carbohydrates than males in the winter. Moreover, larger males with prolonged care present less carbohydrates than smaller males, in contrast to males with recent care where there is a positive relationship between size and carbohydrate content. Our results suggest that parental care in A. dilatatus may be a sexually‐selected trait, as has been found in related species, and further experiments could test this idea. This is the first study to provide evidence of physiological costs related to exclusive paternal care in arthropods.     

Foraging strategies in orb-spinning spiders: Ambient light and silk decorations in Argiope aetherea Walckenaer (Araneae: Araneoidea)

Abstract Many species of orb-spinning spiders construct silk decorations within the structure of the orb-web. The evolutionary significance of these decorations is poorly understood, but the silk decorations of many species reflect UV light, suggesting that they may function to attract insects. In these species, relatively more silk decoration may be required under dimmer light conditions in order to maintain a constant UV-reflecting signal, and hence level of insect attraction. We investigated experimentally whether the orb-spinning spider Argiope aetherea adjusts the amount of silk decoration added to the web according to light conditions. Consistent with the prey-attracting function, we found that spiders adjusted the quantity of silk decoration to their webs, adding more silk decoration when the web was located in dim light rather than bright light.     

The costs of infant carrying in captive cotton-top tamarins

Marmosets and tamarins have a communal rearing system in which all group members help to care for the twin infants characteristic of this family of primates. Helpers are likely to incur time and energy costs by contributing to infant care. Predictions that cotton-top tamarin (Saguinus oedipus) helpers would change their behavior when carrying infants because of reduced mobility and/or a need for increased vigilance were tested in a captive colony. Tamarins carrying an infant spent significantly less time feeding, foraging, moving, or engaging in social activities such as grooming than they did when not carrying. Frequencies of scratching, autogrooming, and scent marking were significantly reduced in carriers, suggesting that their mobility was reduced. However, carriers were significantly less likely to be vigilant (measured by direction of gaze) than when not carrying. Further observations showed that carriers spent more time in concealed areas than they did when not carrying and were probably therefore adopting a cryptic strategy to reduce predation risks to themselves and to infants. These results demonstrate that tamarin helpers pay costs by carrying infants. Some possible compensating benefits are indicated.     

The Effect of Infant Body Mass on Carrier Travel Speed in Cotton-top Tamarins (Saguinus oedipus)

Infant carrying is common in primates and may be the second most costly activity related to reproduction, after lactation. In cooperative breeding groups of callitrichids, all group members carry and care for twin infants. Previous studies have described the costs of infant carrying in terms of body mass loss and reduced locomotor capability. However, infant carrying may also influence travel speed, an important potential cost because slower speed may handicap foraging, energetic budgets, and predator avoidance. We evaluated the impact of infant carrying on the travel speed of 27 adult and 9 subadult cotton-top tamarins (Saguinus oedipus) of both sexes in large outdoor enclosures. We compared carrier speed to speed when not carrying during the 10 weeks after nine births. Subadult tamarins, which have a lower body mass than adults do, moved faster than adults when not carrying. We found no difference between the mean speeds of subadults and adults while carrying. However, the speed of carriers decreased as infant mass increased, and the slope of this negative relationship was more pronounced in subadult carriers. For every 80 g of extra mass load (the body mass of newborn twins), adults reduced their speed by 6 % and subadults by 19 % relative to noncarrying speed. We also observed a reduction in speed while carrying two infants in adult tamarins as carrying time increased. Our results contribute to an understanding of the costs of infant carrying, and serve to emphasize the importance of cooperative breeding systems in coping with these costs.     

Ant predation and the cost of egg carrying in the golden egg bug: experiments in the field

Golden egg bug ( Phyllomorpha laciniata ) females lay eggs on the backs of both female and male conspecifics. Bugs receive eggs voluntarily and involuntarily, and even when males carry eggs, many eggs are not fertilised by the carrier. Carrying the eggs of another individual is unexpected, particularly if egg carrying bears a cost in survival. We examined the predation risk associated with egg carrying experimentally in the field. P . laciniata individuals were enclosed with workers of one of two ant species, Pheidole pallidula or Cataglyphis piliscapus, which co-occur with the bug in the wild. Pheidole pallidula workers preyed on golden egg bugs and their eggs, but Cataglyphis piliscapus workers did not . In P. pallidula enclosures, golden egg bugs carrying larger egg loads were eaten first. These results suggest that golden egg bugs experience high predation pressure and that egg carrying increases the risk of predation. Due to the direct survival costs associated with egg carrying and the lack of relatedness between the eggs and the carrier, we suggest the golden egg bug as the first known intraspecific parasite in which parasitism is not related to active parental care.     

The role of play objects and object play in human cognitive evolution and innovation

In this contribution, we address a major puzzle in the evolution of human material culture: If maturing individuals just learn their parental generation's material culture, then what is the origin of key innovations as documented in the archeological record? We approach this question by coupling a life‐history model of the costs and benefits of experimentation with a niche‐construction perspective. Niche‐construction theory suggests that the behavior of organisms and their modification of the world around them have important evolutionary ramifications by altering developmental settings and selection pressures. Part of Homo sapiens' niche is the active provisioning of children with play objects — sometimes functional miniatures of adult tools — and the encouragement of object play, such as playful knapping with stones. Our model suggests that salient material culture innovation may occur or be primed in a late childhood or adolescence sweet spot when cognitive and physical abilities are sufficiently mature but before the full onset of the concerns and costs associated with reproduction. We evaluate the model against a series of archeological cases and make suggestions for future research.