Modelling hydration and photosystem II activation in relation to in situ rain and humidity patterns: a tool to compare performance of rare and generalist epiphytic lichens

A dynamic water and activity model was developed to assess how efficiently lichens can exploit in situ rain and humid air. The capacity to rehydrate and activate photosynthesis [i.e. photosystem II (PSII)] by these water sources was compared among four hydrophilic and one generalist epiphytic lichen. Hydration status, potential (instant activation) and realized (delayed activation) day‐light activity were simulated using a model based on species‐specific hydration, PSII activation characteristics and in situ water content for Platismatia norvegica in three microclimatic scenarios. The results showed that delayed PSII activation could have profound effects on lichens' ability to exploit environmental water sources. During rain, realized activity was reduced by 19, 34 and 56% compared to simulations assuming instant activation for three hydrophilic lichens in the driest microclimate. During humid air, the reduction was 81% for the most extreme species and scenario, because of slow hydration and low equilibrium water content. Many and brief hydration events may thus hamper species with slow activation and fast desiccation kinetics. No evidence of compensation by a ‘water‐holding’ morphology was observed among studied species. The developed model may provide a tool for identifying suitable habitats for long‐term persistence of lichens with physiological constraints.     

Species‐specific activation time‐lags can explain habitat restrictions in hydrophilic lichens

Photosystem II (PSII) activation after hydration with water or humid air was measured in four hydrophilic and a generalist lichen to test the hypothesis that slow activation might explain habitat restriction in the former group. For the hydrophilic species, activation was after 4 h nearly completed in Lobaria amplissima and Platismatia norvegica, while only c. 50% for Bryoria bicolor and Usnea longissima. The generalist Platismatia glauca was activated instantaneously. The effect of this on lichen field performance was investigated using a dynamic model separating the two water sources rain and humid air. Model simulations were made using the species‐specific characteristics and climate data from 12 stream microhabitats. For U. longissima, slow PSII activation could reduce realized photosynthesis by a factor of five. Bryoria bicolor was almost as severely affected, while P. norvegica displayed moderate reductions. Lobaria amplissima displayed longer realized activity periods even in unfavourable microclimates, possibly because of a higher water loss resistance. Both close proximity to streams and presence of turbulent water had a positive impact on realized activity among the slowly activated species, coinciding with observed distribution patterns of hydrophilic species. The results presented here may thus partly explain observed habitat restrictions of rare hydrophilic lichens.     

A meta‐analysis of ant social parasitism: host characteristics of different parasitism types and a test of Emery’s rule

Abstract 1. In ant social parasitism, the process by which parasite–host systems evolved and the types of invasion mechanisms parasites use are being debated. Emery’s rule, for example, states that social parasites are the closest relatives to their hosts. The present study uses previously published data to test whether Emery’s rule applies equally to all parasitism types (i.e. xenobiosis, temporary, dulosis, and inquilinism). In addition, this study also investigates other links between parasite–host relatedness and host biology, which has implications for understanding the invasion mechanisms used by certain parasites. 2. We find that xenobiotic parasites typically use distantly‐related host species that are of at least medium colony size. Temporary parasites often have multiple host species that are very closely related to the parasite and hosts with medium‐size colonies. Dulotic parasites frequently have multiple host species that are slightly less related and of any size. Lastly, inquiline parasites tend to have a single, very closely related, host species with medium‐size colonies. 3. Parasites tend to be more closely related to host species if they have a single host species or when the host has a large colony size. In contrast, parasites with multiple host species or hosts of small colony size tend to be less related to their hosts. 4. This study is the first to examine trends in ant social parasitism across all known parasite species. Our meta‐analysis shows that Emery’s rule applies to inquilinism and temporary parasitism, but not to dulosis and xenobiosis. Our results also suggest that both parasitism type and parasite–host relatedness predict the number of hosts and host colony size. It may be that a chemical mimicry mechanism allows invasion of large host colonies, but requires close relatedness of parasite and host, and concentration on a single host species.     

ISOLATION OF CYTOCHROME OXIDASE COMPLEX FROM SEA URCHIN MITOCHONDRIAL INNER MEMBRANES

Cytochrome oxidase complex has been isolated and purified from sea urchin mitochondrial inner membranes. The complex exhibited a discrete number of bands in PAGE and a 17 kDa band was recognized by an anti-human subunit IV antibody. No bands were recognized by an anti-yeast hsp60 antibody and an anti-sea urchin β ATPase subunit.     

The ecology of the avian brain: food-storing memory and the hippocampus

Some species of birds store food, often hoarding several hundreds of seeds over a period of just a few weeks. Field and laboratory studies have demonstrated that food-storing species have an impressive memory and an enlarged region of the brain, the hippocampal region. Lesion experiments have shown that the hippocampus is important in accurate retrieval of stored food. Taken together, these results have led to the hypothesis that the enlarged hippocampus is associated with the memory requirements of retrieving stored food. In this review, we discuss four areas of study: comparative studies of the brain, comparative studies of behaviour, developmental plasticity and seasonal changes in food storing and the hippocampus.     

OPTIMIZATION OF PROCESSING OF PEANUT BEVERAGE1

Peanut beverages were prepared and homogenized at 2000, 4000, and 6000 psi and processed at 100°C for 10, 15, and 20 min and at 121°C for 5, 10, and 15 min. Sensory analysis, gas chromatographic (GC) analysis, and viscosity measurements were performed on the products. Sulfur aromatic was found sufficient to discriminate between samples processed at 100°C whereas sulfur aromatic, cooked peanut flavor, and bitterness provided the most efficient combination for discriminating between samples processed at 121°C. Processing time had a more significant effect on the sensory attributes of products. Optimum conditions for processing were found to be at homogenization pressure > 3100 psi and process time > 16 min at a processing temperature of 100°C. No sensory characteristic of the peanut beverage correlated with the instrumental analyses done.     

Cytoplasmic Free Ca2+ in the Marine Alga Acetabularia: Measurement with Ca2+ -selective Microelectrodes and Kinetic Analysis

Neutral carrier–based Ca²⁺ –selective microelectrodeshave been examined for application in concentrated multi–ionsolutions. Calculations with data from the literature and ourcalibration series with Ca²⁺ –EGTA buffers (a convenientalgorithm for theircalculation is given) provide the physico–chemicalconditions for determination of submicromolar concentrationsof free Ca²⁺ in the cytoplasm (with about 400 mM K⁺ and 70 mMNa⁺) of the marine alga Acetabularia acetabulum. The experimentalresults give a cytoplasmic concentration of 560 nM free Ca²⁺corresponding to 140 nM activity. Recordings of cytoplasmicCa²⁺ uponremoval and re-addition of external (10 mM) Ca²⁺ showsteady–state changes by about 50 nM (following the directionof external Ca²⁺) which are preceded by transient over shoots.These kinetics are better described by damped oscillations ofa feedback control system than by two superimposed exponentials.Using the maximum rate of decrease of cytoplasmic Ca²⁺ uponremovalof external Ca²⁺, a unidirectional Ca²⁺ efflux of 0.3µmol m^–2 s^–1 is determined which is consideredto mark the steady–state turnover of Ca²⁺ at the plasmalemma.This high rate and the high electrochemical driving force forCa²⁺ (about – 580 mV)across the plasmalemma at a restingvoltage of about – 170 mV, point to a powerful Ca²⁺ transportsystem which cannot sufficiently be fuelled by ATP–hydrolysisbut requires additional energy Key words: Acetabularia, Ca²⁺–selective microelectrode, cytoplasmic free calcium, EGTA–buffer, homeostasis, plasmalemma     

Soul and Mind: Linguistic Evidence for Ethnopsychology and Cultural History

The author shows that the Russian word duša 'soul' has a much wider scope of use than the English word soul and that it embodies a different folk psychology (fully congruent with what has been described as the Russian "national character"). She also shows that the English word mind stands for an Anglo-Saxon folk category, which has been reified as an objective category of thought. She links the decline and fall of the concept soul and the ascendancy of mind in English with changes in the cultural history and in the prevailing Western ethnophilosophy.     

An Interview with Juan Jose García, President of Ojo de Agua Comunicación

This is an interview with Zapotec video maker Juan Jose Garcia, president of the award-winning media organization Ojo de Agua Comunicacion, in Oaxaca, Mexico. He presents a brief history of native video in Mexico and discusses issues such as indigenous video production and circulation, thematic content, communal practices, relation to indigenous communities, funding, and current projects of his group.