Honeydew: A food resource or arrestant for the mealybug predatorCryptolaemus montrouzieri?

The study investigated whether honeydew is a source of food or is an arrestant stimulus for adults and 4th instar larvae ofCryptolaemus montrouzieri. Adult predators fed on honeydew but produced few viable eggs. In the presence of honeydew the adult and larvae spent a significantly longer time searching and made more intensive searches on leaf surfaces than on clean parts of the leaf. We concluded that the honeydew was both a food resource and an arrestant.

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Résumé Ce travail a pour but de déterminer si le miellat est une source de nourriture ou un stimulus d'arrêt pour les adultes et les larves de 4° stade deCryptolaemus montrouzieri. Les prédateurs adultes nourris de miellat produisent peu d'œufs viables. L'adulte et la larve de coccinelle font des recherches significativement plus longues et plus intensives sur les surfaces foliaires couvertes de miellat que sur les parties indemnes de miellat. L'étude conclut que le miellat constitue à la fois une source de nourriture et un stimulus d'arrêt.

     

Looking for food in all the right places?

Examining a potential functional role for growth hormone secretagogue receptors in the hippocampus, Diano and colleagues (Diano et al., 2006), demonstrate novel actions of the orexigenic peptide ghrelin in hippocampal synaptic architecture, LTP, and learning and memory. These data suggest functional links between metabolic signaling and higher neural function.     

Cellulose and cellulases: Food for thought,food for the future?

Cellulose, a vast and renewable resource and a potential source of food is currently very much underutilized. This review deals with the molecule itself, the uses to which it might be put and, cellulases, the enzymes that may convert potential to reality.     

Towards a mechanistic understanding of the impacts of nitrogen deposition on producer–consumer interactions

Nitrogen (N) deposition has increased substantially since the second half of the 20th century due to human activities. This increase of reactive N into the biosphere has major implications for ecosystem functioning, including primary production, soil and water chemistry and producer community structure and diversity. Increased N deposition is also linked to the decline of insects observed over recent decades. However, we currently lack a mechanistic understanding of the effects of high N deposition on individual fitness, species richness and community structure of both invertebrate and vertebrate consumers. Here, we review the effects of N deposition on producer–consumer interactions, focusing on five existing ecological frameworks: C:N:P ecological stoichiometry, trace element ecological stoichiometry, nutritional geometry, essential micronutrients and allelochemicals. We link reported N deposition-mediated changes in producer quality to life-history strategies and traits of consumers, to gain a mechanistic understanding of the direction of response in consumers. We conclude that high N deposition influences producer quality via eutrophication and acidification pathways. This makes oligotrophic poorly buffered ecosystems most vulnerable to significant changes in producer quality. Changes in producer quality between the reviewed frameworks are often interlinked, complicating predictions of the effects of high N deposition on producer quality. The degree and direction of fitness responses of consumers to changes in producer quality varies among species but can be explained by differences in life-history traits and strategies, particularly those affecting species nutrient intake regulation, mobility, relative growth rate, host-plant specialisation, ontogeny and physiology. To increase our understanding of the effects of N deposition on these complex mechanisms, the inclusion of life-history traits of consumer species in future study designs is pivotal. Based on the reviewed literature, we formulate five hypotheses on the mechanisms underlying the effects of high N deposition on consumers, by linking effects of nutritional ecological frameworks to life-history strategies. Importantly, we expect that N-deposition-mediated changes in producer quality will result in a net decrease in consumer community as well as functional diversity. Moreover, we anticipate an increased risk of outbreak events of a small subset of generalist species, with concomitant declines in a multitude of specialist species. Overall, linking ecological frameworks with consumer life-history strategies provides a mechanistic understanding of the impacts of high N deposition on producer–consumer interactions, which can inform management towards more effective mitigation strategies.     

What has stopped the cycles of sub-Arctic animal populations? Predators or food?

The populations of many species of sub-Arctic animals have recently ceased to fluctuate cyclically. The ultimate cause of this would seem to be changes in the weather, and the proximate cause has been credited to less winter snow allowing predators better access to their prey, thus enabling them to prevent surges in the prey's abundance. But there is evidence that this is not so; that, rather, the numbers of predators are limited by the abundance of their prey. Furthermore, there is alternative evidence that suggests that changes in the cyclical availability of food, brought about by changing weather conditions, may be dampening fluctuations in the abundance of these populations. On the wider ecological front, the evidence presented here further supports the commonality of how a shortage of food of a quality that can support breeding, not the action of predators, generally limits the abundance of populations of both prey and predator.     

Does competition for food imply skewness?

In numerous natural and laboratory populations of animals and plants, overcrowding and resource (food) shortages tend to produce positively skewed and increasingly dispersed distributions of individual weights (as contrasted to symmetric distributions in the conditions of resource abundance). Stochastic models of populations of individuals (animals) competing for resources are considered to account for this phenomenon. The modeling is successful in qualitatively reproducing the dependence of weight distributions on the resource amount and on the number of individuals competing. For a single laboratory population for which detailed data were available, one of the models employed provides an approximate quantitative fit. These findings provide one more argument that, in ecology and elsewhere, modeling of population dynamics should involve the consideration of interindividual variation.     

Mate for the heart: pulsatile or continuous?

At the AHA meeting 2009 it was reported by the press media (and meanwhile published in the N Engl J Med by Slaughter et al., 3 December 2009), that a ‘new type of device more than doubles the two-year survival rate among heart failure patients. The new device, called HeartMate II, improves survival, is more durable, and is linked to better quality of life. The device works by pumping blood continuously rather than simulating a heart beat as older pumps do. The pump is connected to equipment outside the body – a small computer and batteries that the patient wears in a belt pack or harness using a wire from the patient’s abdomen. The FDA has approved the device only as a temporary bridge to transplant.’     

Domiciliary care for the elderly sick--economy or neglect?

This paper reports an investigation of the costs of domiciliary care for 139 elderly sick patients under the care of the home nursing service. The data suggest that there may be little economic advantage in home care for seriously disabled elderly people. The revenue cost of domiciliary care was equal to or greater than the average associated with residential or hospital custodial care in such patients. Even so, the cost of services received at home did not disclose the real need for domiciliary care, since at present this is obscured by compulsory rationing and the separation of responsibility between health and social services. It is suggested that the supposed economic advantage of domiciliary care will depend increasingly on restricting such services, thus increasing the degree of neglect to some patients.