Grapevine leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves influenced by the grape leafhopper,Empoasca vitis

The impact of the grape leafhopper,Empoasca vitis, on leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves of the grapevines,Vitis vinifera L., was studied. Gas exchange was measured on the discolored (red) and the green parts of infested main leaves and on leaves from uninfested vines. Photosynthesis and mesophyll conductance were severely reduced on main leaves showing leafhopper feeding symptoms. The stomatal conductance of the red leaf section of infested main leaves was lower than on undamaged control leaves. Additionally, the red leaf section of infested main leaves showed lower transpiration rates when compared to the green parts of the same leaves and to undamaged control leaves. Gas exchange processes of lateral leaves were not affected by leafhopper feeding. Leafhopperload on main leaves was correlated to visual damage symptoms. At 71.8 leafhopper-days per leaf up to 40% of the main leaf area of the infested plants was discolored from the borders towards the center. Lateral leaves showed no feeding symptoms. Shoot diameter, pruning weight and carbohydrate reserves in the wood were not affected by leafhoppers. Lateral leaf area growth was significantly stimulated on plants infested by leafhoppers. No decrease in yield and fruit quality with leafhopper-loads up to 71.8 leafhopper-days per leaf were observed.     

Relictual physiological ecology in the threatened land snail Codringtonia helenae: A cause for decline in a changing environment?

Land snails often exhibit intra-annual cycles of activity interspersed by periods of dormancy (hibernation/aestivation), accompanied by a range of behavioural and physiological adaptations to ensure their survival under adverse environmental conditions. These adaptations are useful to understand species-specific habitat requirements and to predict their response to environmental changes. We examined the seasonal physiological and biochemical composition patterns of the threatened land snail Codringtonia helenae, endemic to Greece, in relation to its behavioural ecology and climatic conditions. Fuel reserves (glycogen, lipids, proteins) and water were accumulated prior to aestivation, but subsequently were rapidly depleted. LDH exhibited substantial rise during aestivation, suggesting that anaerobic pathways may provide additional energy. The major outcome of our study was the unambiguous discrimination of the four life-cycle periods. Most remarkable was the clear distinction of the aestivation period, with hibernation, the other dormancy period, showing similarity with the two active periods but not with aestivation. We observed disassociation between behavioural and physiological responses and climatic conditions. The physiological responses of C. helenae were effective during hibernation, but only partly compensate the effect of adverse conditions during aestivation, since its aestivating behaviour is occasional and time limited. Perhaps, the behavioural ecology of Codringtonia is relictual and shaped during past environmental conditions. This constitutes an important extinction threat considering the current climatic trends and the deterioration of the habitat of that species due to human activities.     

Physiological and metabolic adjustments of Hoplosternum littorale (Teleostei,Callichthyidae) during starvation

All animals face the possibility of limitations in food resources that could ultimately lead to mortality caused by starvation. The primary goal of this study was to characterize the various physiological strategies that allow fish to survive starvation. A multiparametric approach, including morphological biomarkers, blood plasma metabolites, oxidative stress and energy reserves, was used to assess starvation effects on the fish Hoplosternum littorale. Adult specimens were maintained at four experimental groups: control (fed ad libitum), and starved (not fed) fish for 7 and 28 days. Significant changes were observed not only after 28 days, but also after 7 days of starvation. In the shorter period, the hepatosomatic index as well as plasma triglycerides and glucose were significantly lower in starved fish than in the control ones. These results were accompanied by reduced lipid, glycogen and protein reserves in liver and diminished glycogen content in muscle, suggesting the need of these macromolecules as fuel sources. In addition, increased antioxidant enzyme activities were observed in gills, without evidence of oxidative stress in any of the evaluated tissues. Most significant differences were found in 28-days starved fish: total body weight together with the hepatosomatic index was lower when compared to control fish. The plasmatic metabolites tested (glucose, triglyceride, cholesterol and protein), all energy reserves in liver and glycogen content in muscle decreased in 28-days starved fish. Lipid oxidative damage was reported in liver, kidney and brain, and antioxidant enzymes (GST, GR, GPx and CAT) were activated in gills. According to the multivariate analysis, oxidative stress markers and metabolic parameters were key biomarkers that contributed in separating starved from fed fish. Our study allowed an integrated assessment of the fish response to this particular condition.     

Latitudinal differences in somatic energy storage: adaptive responses to seasonality in an estuarine fish (Atherinidae: Menidia menidia)

This study focuses on the seasonal accumulation and depletion of somatic energy in the Atlantic silverside (Menidia menidia), an annual estuarine fish. Previous research revealed that northern silversides are subject to strong size-dependent winter mortality, while southern fish suffer no appreciable winter mortality. To examine whether there was geographic differentiation in allocation strategies, we compared temporal patterns of energy storage and utilization among three populations along this gradient in seasonality. The comparative design used monthly or biweekly samples of fish collected in the wild, as well as samples of fish from each population reared in a common environment, where genetic differences can be clarified. Somatic energy stores were quantified via gravimetric analysis of neutral storage lipids and lean tissue. Analysis revealed that small individuals maintained relatively low levels of lipid reserves, which may account for their lower survival in winter. Wild fish in the north rapidly accumulated large somatic reserves, which were depleted over the winter and then increased again during the subsequent spring breeding season. In wild southern fish, relatively small reserves accumulated slowly until breeding commenced in the spring. The common-environment comparison of somatic storage patterns revealed a genetic basis for among-population differences in reserve accumulation rates, but no differences in the amount of reserves stored. We conclude that the overwinter depletion of somatic reserves has a significant selective impact on energy accumulation and allocation strategies in seasonal environments. Received: 1 November 1995 / Accepted: 13 September 1996     

Does body size influence nest attendance? A comparison of Ross’s geese (Chen rossii) and the larger, sympatric lesser snow geese (C. caerulescens caerulescens)

The body-size hypothesis predicts that nest attendance is positively related to body size among waterfowl and that recess duration is inversely related to body size. Several physiological and behavioral characteristics of Ross’s geese (Chen rossii) suggest that females of this species should maintain high nest attendance despite their relatively small body size. Accordingly, we used 8-mm films to compare the incubation behavior of Ross’s geese to that of the larger, closely-related lesser snow geese (C. caerulescens caerulescens; hereafter, snow geese) nesting sympatrically at Karrak lake, Nunavut, Canada in 1993. We found that nest attendance averaged 99% for both species. Our results offer no support for the body-size hypothesis. We suggest that temperature requirements of embryos in relation to short incubation duration and a low foraging efficiency of females select for high nest attendance in both snow geese and Ross’s geese.     

Annual coral bleaching and the long-term recovery capacity of coral

Mass bleaching events are predicted to occur annually later this century. Nevertheless, it remains unknown whether corals will be able to recover between annual bleaching events. Using a combined tank and field experiment, we simulated annual bleaching by exposing three Caribbean coral species (Porites divaricata, Porites astreoides and Orbicella faveolata) to elevated temperatures for 2.5 weeks in 2 consecutive years. The impact of annual bleaching stress on chlorophyll a, energy reserves, calcification, and tissue C and N isotopes was assessed immediately after the second bleaching and after both short- and long-term recovery on the reef (1.5 and 11 months, respectively). While P. divaricata and O. faveolata were able to recover from repeat bleaching within 1 year, P. astreoides experienced cumulative damage that prevented full recovery within this time frame, suggesting that repeat bleaching had diminished its recovery capacity. Specifically, P. astreoides was not able to recover protein and carbohydrate concentrations. As energy reserves promote bleaching resistance, failure to recover from annual bleaching within 1 year will likely result in the future demise of heat-sensitive coral species.     

Valuation and sustainable use of tropical rainforest

Studies of the extraction of non-timber forest products have shown that the standing rainforest may be more valuable than alternatives involving deforestation

Although this article is about placing a value on rainforest, it begins by stressing the importance and value of rainforest for its environmental function, particularly for the control of world climate patterns. It is then shown how rainforest peoples depend on the plants around them and in some study areas were found to have a use for every tree on the one-hectare plots. It is therefore not surprising that the rainforest can contain many non-timber forest products (NTFPs) of commercial potential, some of which such as rubber latex and Brazil nuts have been in the market economy for many years. A summary is given of various attempts to place a value on rainforest for its NTFPs. Each of the three studies showed that the extraction of these products could be more valuable than alternative land uses involving deforestation. Various rainforest countries such as Brazil, Guatemala, and Indonesia have set up extractive reserves where local people are allowed to extract NTFPs but not to clear cut the forest. Extractive reserves have slowed down deforestation in some areas, but only provide a meagre subsistence existence for their inhabitants, so while they are useful, they are not a panacea that will solve all the conservation problems of tropical rainforest.     

Response of ground-dwelling beetles across logging coupe edges into streamside reserves

Streamside reserves can provide important habitat reservation in forest landscapes subject to logging. Depending on the width of streamside reserves, edge effects have the potential to compromise their effectiveness for terrestrial conservation, yet edge effects into riparian environments have rarely been assessed. It would be unwise to assume that edge effects act in the same way at streamside reserves as at the non-riparian edges of logging coupes, as interactions with riparian influences on beetles along the stream-upslope gradient might create unique edge conditions. In this study, we assess edge effects on ground dwelling beetles at four sites, using transects of pitfall traps across logging coupe edges into streamside reserves that have only been affected by logging on one side of the stream. Edge effects were found to extend further into streamside reserves in this study than into upslope habitat at the same sites from a concurrent study. Edge effects were site specific and appeared to extend as far as the stream in most cases (23–65 m). Comparison of beetle assemblage composition with adjacent unlogged streams supported the conclusion that beetles within 10 m of streams in streamside reserves were still responding to edge effects. These results suggest that streamside reserves might not contain habitat comparable with riparian areas away from the influences of nearby clearfelling, and wider reserves are recommended to maintain core habitat not compromised by edge effects.     

Marine no-take zone rapidly benefits endangered penguin

No-take zones may protect populations of targeted marine species and restore the integrity of marine ecosystems, but it is unclear whether they benefit top predators that rely on mobile pelagic fishes. In South Africa, foraging effort of breeding African penguins decreased by 30 per cent within three months of closing a 20 km zone to the competing purse-seine fisheries around their largest colony. After the fishing ban, most of the penguins from this island had shifted their feeding effort inside the closed area. Birds breeding at another colony situated 50 km away, whose fishing grounds remained open to fishing, increased their foraging effort during the same period. This demonstrates the immediate benefit of a relatively small no-take zone for a marine top predator relying on pelagic prey. Selecting such small protected areas may be an important first conservation step, minimizing stakeholder conflicts and easing compliance, while ensuring benefit for the ecosystems within these habitats.     

A teleonomic model describing performance (body, milk and intake) during growth and over repeated reproductive cycles throughout the lifespan of dairy cattle. 2. Voluntary intake and energy partitioning

This is the second of two papers describing a teleonomic model of individual performance during growth and over repeated reproductive cycles throughout the lifespan of dairy cattle. The model described in the first paper is based on the coupling of a regulating sub-model of the dynamic partitioning of a female mammal's priority over a lifetime with an operating sub-model of whole-animal performance. The model provides a reference pattern of performance under normal husbandry and feed regimen, which is expressed in this paper in a reference dynamic pattern of energy partitioning adapted to changes in nutrient supply. This paper deals with the representation of deviations from the reference pattern of performance. First, a model of intake regulation, accounting for feed allowance, physical limitation of the digestive tract and energy demand, is used to determine the actual intake, which may generate a deviation from the energy input under the reference pattern of partitioning. Second, a theoretical model is proposed to apportion the energy deviation between flows involved in performance and thus simulate lifetime performance when actual intake is above or below requirements. The model explicitly involves a homeorhetic drive by way of the tendency to home on to the teleonomic trajectory and a homeostatic control by way of the tendency to maintain an energy equilibrium in response to nutritional constraints. The model was evaluated through simulations reproducing typical feeding trials in dairy cows. Model simulations shown in graphs concern the effect of dietary energy content on intake, body weight and condition score, and milk yield. Results highlight the ability of the model to simulate the combination of physical and energetic regulation of intake, the accelerated, retarded and compensatory patterns of growth and the short- and long-term residual effects of pre-partum feeding on lactation.