Chlorophyll fluorescence images demonstrate variable pathways in the effects of plasma membrane excitation on electron flow in chloroplasts of <Emphasis Type=Italic>Chara</Emphasis> cells

Chlorophyll fluorescence Imaging and Microscopy PAM fluorometry were applied to study spatial dynamics of photosystem II quantum yield ( DF/F_m￠ ) left( {Delta F/F_m^prime } right) and non-photochemical quenching (NPQ) in resting and electrically stimulated Chara corallina cells in the absence and presence of the hydrophilic electron acceptor methyl viologen (MV) in the external medium. Electrical excitation of the plasma membrane temporarily enhanced the heterogeneity of photosynthetic patterns under physiological conditions (in the absence of MV), but irreversibly eliminated these patterns in the presence of MV. These findings suggest that the action potential (AP) of the excitable plant cell affects the spatial patterns of photosynthesis and chlorophyll fluorescence through different pathways operated in the absence and presence of MV. Based on the extent of NPQ as an indicator of MV-dependent electron flow, it is supposed that MV cannot permeate into the chloroplasts of photosynthetically active “acid cell regions” but gains an immediate access to the stroma of these chloroplasts after triggering of an AP. The AP-triggered MV-dependent non-photochemical quenching in the chloroplasts of acidic cell regions was routinely observed at 0.1 mM Ca²⁺ in the medium but not at elevated (2 mM) external Ca²⁺ concentration. The results are interpreted in terms of competition between two permeant divalent ion species, Ca²⁺ and MV²⁺, for their passage through the voltage-gated calcium channels of the plasma membrane. It is proposed that the herbicidal activity of MV in characean cells, here serving as model object, can be manipulated by triggering AP and varying Ca²⁺ concentration in the environmental medium.     

Development of infant common marmosets’ (<Emphasis Type=Italic>Callithrix jacchus</Emphasis>) preference for their parents over adults from another group

Parent–offspring attachment is important for animals which have offspring that require parental care for their development. Infant attachment to the mother has been examined in macaques, but it remains poorly understood in common marmosets. Here, we examined the abilities of 14 common marmoset infants to show preference for their parents over adults from another group at the ages of 4, 10, and 15 weeks. Each infant was exposed to its parent and an adult from another group in an I-shaped maze. Although 4-week-old infants did not show a significant difference between approach behaviors toward their parents and other adults, 10- and 15-week-old infants approached and stayed longer near their parents than adults from another group. These results suggest selective approach behavior develops in marmosets by the age of 10 weeks.     

Convergent Patterns of Body Shape Differentiation in Four Different Clades of Poeciliid Fishes Inhabiting Sulfide Springs

We investigated replicated differentiation in four lineages of livebearing fishes (two with the genus Poecilia and two within Gambusia), which inhabit freshwater habitats and have also colonized sulfide springs in Oklahoma, Mexico, and Venezuela. Sulfide springs are characterized by extreme hypoxia and high concentrations of toxic hydrogen sulfide, which provide a strong source of divergent selection compared to adjacent non-sulfidic habitats. Using geometric morphometric analysis of body shape, we found that sulfide spring populations significantly differ from relatives from regular freshwater habitats in all four lineages investigated. Differentiation is characterized by strong patterns of convergent evolution, with sulfide spring populations consistently exhibiting an increase in head size, even though the magnitude and nature differences varied across lineages. Head size is strongly correlated with an increase in gill size in sulfide spring populations of the genus Poecilia, which facilitates efficient oxygen acquisition in the hypoxic H₂S-environment and directly affects survival. The convergent patterns of differentiation support previous findings about the effects of sulfide on trait evolution.     

Multiple Limit Cycles in a Gause Type Predator–Prey Model with Holling Type III Functional Response and Allee Effect on Prey

This work aims to examine the global behavior of a Gause type predator–prey model considering two aspects: (i) the functional response is Holling type III and, (ii) the prey growth is affected by the Allee effect. We prove the origin of the system is an attractor equilibrium point for all parameter values. It has also been shown that it is the ω-limit of a wide set of trajectories of the system, due to the existence of a separatrix curve determined by the stable manifold of the equilibrium point (m,0), which is associated to the Allee effect on prey. When a weak Allee effect on the prey is assumed, an important result is obtained, involving the existence of two limit cycles surrounding a unique positive equilibrium point: the innermost cycle is unstable and the outermost stable. This property, not yet reported in models considering a sigmoid functional response, is an important aspect for ecologists to acknowledge as regards the kind of tristability shown here: (1) the origin; (2) an interior equilibrium; and (3) a limit cycle of large amplitude. These models have undoubtedly been rather sensitive to disturbances and require careful management in applied conservation and renewable resource contexts.     

Phytotoxic effects of β-pinene on early growth and associated biochemical changes in rice

β-Pinene, an oxygenated monoterpene, is one of the major monoterpenes emitted into the atmosphere from forest areas and trees. Besides, it is a principal component of essential oils of a number of aromatic plants, which are involved in a variety of ecological interactions, including allelopathy, in the natural environment. However, studies pertaining to phytotoxicity and biochemical effect(s) of β-pinene are largely lacking. We investigated the effect of β-pinene (0.02, 0.04, 0.08, 0.20, 0.40 and 0.80 mg/ml) in a dose- and time-dependent manner on early seedling growth, dry weight accumulation, photosynthetic pigments and changes in macromolecule (protein and carbohydrate) content and activities of enzymes—proteases, α- and β-amylases, polyphenol oxidases and peroxidases- in rice (Oryza sativa) after 3rd, 5th and 7th day of exposure. β-pinene (≥0.04 mg/ml) significantly reduced the root (by 13–87%) and coleoptile (by 5–80%) length of rice. Exposure to β-pinene reduced total chlorophyll content in rice coleoptiles suggesting a negative impact on photosynthesis. The content of macromolecules (proteins and carbohydrates) enhanced significantly in response to β-pinene, whereas the activities of hydrolyzing enzymes—proteases, α-amylases, and β-amylases—declined (by 30–85, 26–84, 27–74%, respectively) in β-pinene-exposed seedlings. In contrast, the activities of peroxidases (POX) and polyphenol oxidases (PPO) enhanced significantly (by 16–152 and 53–290%, respectively) in rice roots in response to β-pinene in a dose- and time-dependent manner. Increased activities of POX and PPO indicate their involvement in providing protection and/or conferring resistance against β-pinene-induced stress. The study concludes that β-pinene inhibits the early growth of rice by altering the plant biochemical status and enhancing activities of POXs and PPOs involved in general plant defense.     

Anti-hemolytic and Peroxyl Radical Scavenging Activity of Organoselenium Compounds: An In Vitro Study

Selenium-containing amino acids, selenocystine (CysSeSeCys), methylselenocysteine (MeSeCys), and selenomethionine (SeMet) have been examined for anti-hemolytic and peroxyl radical scavenging ability. Effect of these compounds on membrane lipid peroxidation, release of hemoglobin, and loss of intracellular K⁺ ion as a consequence of peroxyl radicals-induced oxidation of human red blood cells were used to evaluate their anti-hemolytic ability. The peroxyl radicals were generated from thermal degradation of 2,2′-azobis(2-methylpropionamidine) dihydrochloride. Significant delay (t _eff) was observed in oxidative damage in the presence of the selenium compounds. From the IC₅₀ values for the inhibition of hemolysis, lipid peroxidation, and K⁺ ion leakage, the relative anti-hemolytic ability of the compounds were found to be in the order of CysSeSeCys > MeSeCys > SeMet. The anti-hemolytic abilities of the compounds, when compared with sodium selenite (Na₂SeO₃) under identical experimental conditions, were found to be better than Na₂SeO₃. Relative rate constants estimated for the reaction of MeSeCys and SeMet with peroxyl radicals by competition kinetics using ABTS²⁻ as a reference confirmed that all the compounds are efficient peroxyl radical scavengers. Comparison of the GPx-like activity of these compounds, by NADPH–GSH reductase coupled assay, indicated that CysSeSeCys exhibits the highest activity. Based on these results, it is concluded that among the compounds examined, CysSeSeCys, possessing the ability to reduce peroxyl radicals and hydroperoxides showed efficient anti-hemolytic activity.     

Mantled Howler (<Emphasis Type=Italic>Alouatta palliata</Emphasis>) Arboreal Pathway Networks: Relative Impacts of Resource Availability and Forest Structure

Numerous studies have concluded that primates move about their environments in a nonrandom manner, frequently traveling between consecutive foraging sites along relatively straight-line paths. However, primates do not always take the most direct path between resources, and a number of species have been observed to travel repeatedly along a network of the same arboreal pathways. In this study, I used spatially explicit techniques to examine quantitatively what mantled howler monkey groups on Barro Colorado Island, Panama, accomplish by selecting nonlinear paths between resources and by repeatedly using the same paths within an arboreal network. Results show that chosen arboreal paths between sites where foraging occurred have higher levels of resource availability and canopy connectivity than comparable straight-line paths between the same sites. When comparing the relative importance of these factors, autologistic models of pathway choice indicate that though canopy connectivity is related to the location of repeatedly used arboreal pathway networks, the most statistically significant predictor is resource availability (both on a path and within a visual detection distance of a path). These results provide support for the hypothesis that repeated use of arboreal pathway networks aids in resource monitoring and acquisition. In addition, statistical models developed from 1 primary focal group’s travel patterns had high predictive value when employed to generate likely locations for arboreal pathways in the home ranges of 3 neighboring groups. This finding has important implications for studies of primate habitat use and seed dispersal, as it suggests that different groups consistently use similar characteristics when deciding on travel paths.     

Rank-Related Fitness Differences and Their Demographic Pathways in Semi-Free-Ranging Rhesus Macaques (<Emphasis Type=Italic>Macaca mulatta</Emphasis>)

Researchers have explored the fitness consequences of female dominance hierarchies in many primate populations, with most studies highlighting differences in age of maturation, fertility, and offspring survival. We use resampling techniques and van Tienderen’s (2000) elasticity path analysis to identify rank-related differences in finite rate of increase (λ) and their demographic correlates among segments of a semi-free-ranging rhesus macaque population. Higher-ranking population segments grew at greater rates for some portions of the 40-yr study period. The female members of these segments achieved these lifetime fitness differences through higher fertility and especially higher adult survival rates. This is the first clear evidence that social rank influences female primate adult survival, and is a crucial fitness component for any long-lived, slow-reproducing animal. Traditional methods of comparing lifespans, and other life history variables, among rank categories fail to identify most of the rank-related differences primarily because they require completed life histories that are available only on a small number of the females known in the population.     

All Together Now: The Need for a Combined Empirical and Modeling Approach When Studying Primate Group Coordination

Studies of collective decision making attempt to explain the simultaneous behaviors of many individuals and how these contribute to the behavior observed at a collective level. However, this can be problematic to achieve given the general constraints of field or experimental data. This is particularly the case for primates, and results in limited reproducibility of events and it is difficult to separate the effects of different variables. Advocates of theoretical models have proposed that simple rules of interaction successfully reproduce different phases of group movement and the transitions between them, and greatly contribute to our knowledge of complex phenomena. Models can simulate practically any situation and tell us what response would emerge from it, including complex situations such as group decision making. The general heuristic value of these models has been universally recognized. However, the modeling approach tends to oversimplify real situations, and very few biological validations yet exist. I here suggest that it is essential to confront theoretical results with real data and that the combination of the 2 approaches will substantially improve our comprehension of collective decision making.