Annual changes in body mass in captive Svalbard ptarmigan: role of changes in locomotor activity and food intake

The influence of changes in the amount of locomotor activity on the annual body mass cycle was investigated in captive Svalbard ptarmigan kept indoors at thermoneutrality and exposed to seasonal changes in daylength or continuous light from the summer onwards. In both groups there was a close correlation between locomotor activity and metabolic rate. Only birds exposed to changes in daylength showed an annual cycle in locomotor activity, with low activity in autumn and mid-winter and a peak in spring. The birds permanently exposed to continuous light had a relatively low activity throughout the year with no systematical changes. Body mass began to increase in both groups in early autumn and the food intake was elevated during most of the following fattening period. It is concluded that elevated food intake is the prime factor involved in autumnal fattening in captive Svalbard ptarmigan. Body mass increased significantly faster under decreasing daylength compared with continuous light, associated with a lower activity as well as a higher food intake. The birds exposed to continuous light maintained a high body mass and a relatively low activity level during spring. In birds exposed to changing daylength, body mass fell from late February onwards, which is about 3 months later than in outdoor caged or free-living Svalbard ptarmigan. In the birds exposed to increasing daylength a fourfold increase in the amount of locomotor activity occurred from February to April. This increased activity was correlated with a negative energy balance and may be casually associated with the fall in body mass in these birds. Under outdoor conditions, elevated locomotor activity in spring may be responsible for a continuation of the decline in body mass commencing in November, despite a slight tendency for an increased food intake towards the end of this period.Abbreviations BM body mass - CE _f caloric equivalent of food - EAE energy assimilation efficiency - EE energy expenditure - FI food intake - LA locomotor activity - LL continuous light - LD simulated annual changes in daylength - MEI metabolizable energy intake - MR metabolic rate - RQ respiratory quotient     

Orange roughy otolith growth rates: a direct experimental test of the Romanek–Gauldie otolith growth model

Endolymph chemistry (Ca²⁺, pH, Na⁺) was measured in 17 orange roughy (Hoplostethus atlanticus; Teleostei; Trachichthyidae). Theoretical daily microincrement widths based on the Romanek and Gauldie model of otolith growth were calculated from the measure of otolith chemistry. Theoretical daily microincrement widths were well-correlated (r²=59%) with the width of the last daily microincrement growing at the posterior edge of otoliths taken from the sampled fish.     

Ecological resistance to the invasion of a freshwater clam,Corbicula fluminea: fish predation effects

Summary Fish predation is shown to have a twenty nine fold effect on the abundance of the invasive freshwater clam, Corbicula fluminea, in a Texas reservoir. This predation has prevented the clam from establishing the high densities commonly reported for it elsewhere. The high magnitude of the fish effect is attributed to Corbicula being an invader to this reservoir and not being able to cope well with the mix of resident fish species. In the absence of fish, colonization of the reservoir by Corbicula is spatially patchy. When fish interact with these clams, they remove sufficient numbers of individuals from dense patches to create the appearance of a spatially uniform distribution.     

Maximum feeding potential of larvae and adults ofthe scale insect predator, Chilocorus nigrituswith a new method of estimating food intake

A method of estimating the weight ofindividual Abgrallaspis cyanophylli (Signoret)without the need for removal from the host plant isdescribed. Using this method, which enables accurateestimations of scale insect weight by measuring lengthand relating it to a previously determined regressionmodel, maximum feeding potential in male and femaleChilocorus nigritus (F.) adults was examined atvarious constant temperatures over the range of 13 to30 °C and at a cycling temperature of 12 h/12 hat 14/30 °C (r.h. in the range of 62 to 68%). Mean daily potential food intake varied from 0.097 mg/day at 13 °C to 1.432 mg/day at 30 °C.However, intake at the cycling temperature was significantly higher than that at constant temperatures (1.98 mg/day). At 15, 20 and 30 °C there were no significant differences between male and female potential food requirements whilst at temperatures in the mid range, there was a considerable increase in female potential voracitywhen compared to that of the males. Maximum potentiallarval food requirement for development at 26 °Cand 62% r.h. in C. nigritus was also estimatedusing the above method. A mean of 16.24 mg of Abgrallaspis cyanophylli (Signoret) was required forlarvae of both sexes to complete development. Thisstudy suggests that C. nigritus would be mostefficient as a biological control agent if used inglasshouses with a mean daily temperature above22 °C.     

Limits to food intake and fiber utilization in the prairie vole,Microtus ochrogaster: effects of food quality and energy need

We fed prairie voles (Microtus ochrogaster) rat chow diluted with variable amounts of -cellulose to determine 1) how much fiber the voles could tolerate in their diet; 2) changes in food intake and digestibility of dry matter and of fiber; 3) the extent to which voles utilized fiber as an energy source; and 4) whether any of these variables differed between groups of animals maintained at 5 or 22°C. Fiber content of the diets ranged from 20 to 84%. Animals held at 5°C maintained body mass through a diet containing 69% fiber, while animals held at 22°C maintained body mass through the 84% fiber diet. Dry matter intake increased with fiber level from 9.3 to 15.0 g·day^-1 for animals at 5°C and from 5.6 to 14.0 g·day^-1 for animals at 22°C; intake on the highest fiber diet eaten by either group was not different. Dry matter digestibility decreased significantly as the fiber in the diets increased, but was not affected by temperature treatments. Digestible dry matter intake for each group remained constant regardless of diet quality, but on each diet digestible dry matter intake for animals at 5°C was significantly higher than that of the animals held at 22°C. Digestibility of the fiber portion of the experimental diets remained constant as food quality decreased, so the percent of daily energy need met by fiber utilization increased with higher food intake. On the lowest quality diet each group tolerated, fiber digestion provided approximately 42 and 68% of the energy needs of voles at 5 and 22°C, respectively.Abbreviations BM body mass - BMR basal metabolic rate - DE digestible energy - DM dry matter - DMD dry matter digestibility - DDMI digestible dry matter intake - MR metabolic rate - NDF neutral detergent fiber (=cell walls) - NDS neutral detergent solubles (=cell solubles) - SEM standard error of mean - T _a ambient temperature     

Egg size and egg mass of Daphnia magna: response to food availability

The influence of different food availability on egg size and egg mass in Daphnia magna Straus was studied in long-term experiments using a flow-through system. Daphnia were either kept a constant high or low food levels or subjected to alternating periods of high food and starvation. Some animals were starved continuously after they had deposited their first clutch of eggs. Eggs were measured and weighed and their density (dry mass per volume) was determined. The results support the model of Glazier (1992), which defines a region of reproductive constraint at very low food concentrations and a region of adaptive response as food concentration increase. Egg sizes were largest under continuously low food concentrations (0.1 mg Cl^–1), which indicates that the maximum of Glazier's non-linear response curve is at very low food levels. Eggs produced during starvation were small, probably as a result of reproductive constraints. Egg density was about 0.37 mg dry weight mm^–1 and did not differ between treatments.     

Algal biomass dynamics during colonization of artificial islands: experimental results and a model

Algal biomass during colonization of polyurethane foam islands (5.1 cm × 7.6 cm × 7.6 cm) was approximated by measuring chlorophyll a levels on islands after exposure periods of 1, 2, 3, 4, and 6 weeks at six locations in a small lake in central Tennessee, USA. Chlorophyll, ash-free dry weight, and concurrent environmental data were collected for two colonization periods: one in late winter and spring (Set 1), a second in summer (Set 2).During Set 1 algal biomass levels, as indicated by chlorophyll a, showed a sharp rise initially, but Set 2 islands exhibited a lag period of 7 to 12 days before a rapid increase in algal biomass was noted. Equilibrium chlorophyll a values were similar for both sets. High levels of phaeopigments were found at Stations 2, 3, and 4 during Set 2 resulting in large corrections in chlorophyll a readings. Ash-free dry weight values increased steadily through each colonization period.A model of biomass accumulation during colonization was constructed postulating three major processes — photosynthesis, respiration, and passive accumulation — which were modulated by three environmental factors — light, temperature, and plankton chlorophyll a levels. For simulations parameter values were taken from the literature where possible. Additional parameter values were set and literature values adjusted when the model was tuned to Set 2 data. A simulation with the tuned model using Set 1 environmental input resulted in a good prediction of equilibrium values, but a misinterpretation of initial values. The discrepancy between model predictions and data was alleviated when the passive accumulation rate was increased demonstrating the dependence of biomass values early in colonization on passive accumulation from the plankton.     

Vibrating the food receivers: a direct way of signal transmission in stingless bees (Melipona seminigra)

An element common to the recruitment communication of eusocial bees (honey bees, stingless bees and bumble bees) are pulsed thorax vibrations generated by successful foragers within the nest. In stingless bees, foragers vibrate during the unloading of the collected food. In the present study on Melipona seminigra we demonstrate that during trophallactic contacts, the food receivers are directly vibrated by the foragers. As a consequence, both the temporal structure and the main frequency component of the forager’s vibrations are directly passed on to the receiver. The vibrations are attenuated by about 17 dB on their way from the forager’s thorax (velocity amplitude of the vibrations: ∼70 mm/s) to the receiver’s thorax (∼10 mm/s), the main amount of attenuation (about 12 dB) occurring during transmission from the head of the forager to that of the receiver. Vibrations conducted through the substrate between the forager and food receiver are comparatively small with velocity amplitudes of 0.3 mm/s. Possible ways of perception and the advantages of vibration transmission by direct contact within the recruitment context are discussed.     

Small-scale recruitment variation in a temperate fish: the roles of macrophytes and food supply

Synopsis The availability of reef-related resources, particularly food and shelter can play a significant role in determining the distribution and abundance of reef fishes. Much of the structure on temperate reefs is provided by macroalgae, and variability in the density of temperate reef fishes at large spatial scales (100's of meters) can often be explained by variation in macroalgal cover or density. In this study I investigated the role of macrophytes and associated food resources on the recruitment of a temperate fish, Tautogolabrus adspersus, at a small spatial scale (0.25 m²). No relationship between the density of new recruits and the percent cover of kelp, foliose or filamentous algae was observed. Multiple regressions revealed that less than 8% of variability in recruitment could be explained by variability in macroalgal cover. However, recruits were found in higher abundance in patches containing many functional forms of seaweeds than in patches dominated by a single form. A wide variety of prey were available for use by cunner recruits; however, crustaceans and mussels were the only common components of their diet, and crustaceans were clearly the most preferred prey. The prey composition in patches where fish were present was compared to randomly selected patches. Significantly greater numbers of isopods, amphipods and newly settled mussels were present in patches where fish were present than in randomly selected patches. The data presented in this study contradict previous work that has shown algal structure to be important in determining patterns of abundance and food supply to be of little significance. A conceptual model is proposed suggesting that settling fish select habitats in a hierarchical manner largely based on their dispersal tendencies. Hierarchical selection of habitats results in different attributes of the habitat being selected during different life-history intervals.     

The yeast metabolome addressed by electrospray ionization mass spectrometry: Initiation of a mass spectral library and its applications for metabolic footprinting by direct infusion mass spectrometry

Mass spectrometry (MS) has been a major driver for metabolomics, and gas chromatography (GC)-MS has been one of the primary techniques used for microbial metabolomics. The use of liquid chromatography (LC)-MS has however been limited, but electrospray ionization (ESI) is very well suited for ionization of microbial metabolites without any previous derivatization needed. To address the capabilities of ESI-MS in detecting the metabolome of Saccharomyces cerevisiae, the in silico metabolome of this organism was used as a template to present a theoretical metabolome. This showed that in combination with the specificity of MS up to 84% of the metabolites can be identified in a high mass accuracy ESI-spectrum. A total of 66 metabolites were systematically analyzed by positive and negative ESI-MS/MS with the aim of initiating a spectral library for ESI of microbial metabolites. This systematic analysis gave insight into the ionization and fragmentation characteristics of the different metabolites. With this insight, a small study of metabolic footprinting with ESI-MS demonstrated that biological information can be extracted from footprinting spectra. Statistical analysis of the footprinting data revealed discriminating ions, which could be assigned using the in silico metabolome. By this approach metabolic footprinting can advance from a classification method that is used to derive biological information based on guilt-by-association, to a tool for extraction of metabolic differences, which can guide new targeted biological experiments. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Validation of a planimetric procedure to quantify stress in Littorina littorea (Gastropoda: Mollusca): is it independent of the reproductive cycle?

This study forms part of a larger project in which five planimetric parameters have been used to study changes in the digestive epithelium of Littorina littorea under different environmental and physiological conditions. Our aim was to examine the effect of the reproductive cycle on these parameters in order to assess their usefulness as indicators of stress. A one way anova shows that the absolute parameters of mean epithelial thickness (MET), mean diverticulum radius (MDR) and mean luminal radius (MLR) vary significantly depending on the time of the year. This variation is highly correlated to the amount of digestive tissue present and hence negatively correlated to the reproductive state because gonad and digestive tissue volume are inversely related. Consequently, these parameters are not good indicators of stress. However, whereas the absolute size of the digestive acinus varies with the reproductive state of the animal, the MET, MDR and MLR retain the same proportions and therefore the ratios MET/MDR and MLR/MET remain constant. This makes them useful indicators of stress because they are independent of intrinsic variables such as the reproductive cycle.     

Search orientation in adultDrosophila melanogaster: Responses of rovers and sitters to resource dispersion in a food patch

Drosophila melanogasteradults were employed in single resource patches of varying density and size and in a multiple-patch array to determine the degree to which resource dispersion influences searching success. Individuals from rover and sitter selected lines, with extreme genotypes for local search duration, are not as successful as control-line (wild-type) flies in locating sucrose drops in single patches varying in size and density. The number of new drops located differed significantly between fly lines in all patch types, except in a high-density patch, and within each fly line over the different patch sizes and densities. The similarities in number of drops found by rovers and sitters in all patch types are not reflected in the time periods spent searching. In the multiple-patch array sitters never left the central patch, whereas most rovers and con-trol-line flies found additional patches. The proximate explanations for the success or failure of the three fly lines in different patch sizes and densities relate to the looping locomotor pattern characterizing local search in D. melanogaster.The reactivation of searching each time a drop is ingested or revisited keeps an individual in the immediate vicinity of the last encountered resource. Flies from the selected lines, each exhibiting extreme types of locomotor patterns, leave patches relatively unexploited because local search consists either of rapid, nearly linear movement away from a drop in rovers or of relatively long bouts of local search in sitters, which promotes revisiting rather than locating new drops. Control-line flies locate more drops than either rovers or sitters and in less time than sitters, suggesting that their intermediate phenotype for search behavior allows for more flexibility in searching in various patch sizes and resource densities. The results are discussed with reference to environmental and physiological factors that may modify searching behavior and, possibly, enhance the survival of individuals with extreme genotypes.     

Siderotyping of fluorescent <Emphasis Type="Italic">Pseudomonas</Emphasis>: molecular mass determination by mass spectrometry as a powerful pyoverdine siderotyping method

The numerous pyoverdines so far characterized as siderophores of fluorescent Pseudomonas could be usually differentiated one from each others by the two physico-chemical and physiological methods of siderotyping, i.e., siderophore-isoelectrofocusing and siderophore-mediated iron uptake. As shown in the present paper, the structural diversity of the peptide chain characterizing these molecules results in a very large panel of molecular masses representing 64 different values ranging from 889 to 1,764 Da for the 68 compounds included in the study, with only a few structurally different compounds presenting an identical molecular mass. Thus, the molecular mass determination of pyoverdines through mass spectrometry could be used as a powerful siderotyping method.     

Effects of outbreak of the train millipede Parafontaria laminata armigera Verhoeff (Diplopoda: Xystodesmidae) on litter decomposition in a natural beech forest in Central Japan. 1. Density and biomass of soil invertebrates

Soil invertebrates were studied to determine the animals important in litter decomposition and soil formation in a natural forest of Fagus crenata Blume mixed with Quercus mongolica var. grosseserrata Rehd. et Wils., where outbreak of the adult train millipede, Parafontaria laminata armigera Verhoeff was recorded in 1980. The density and biomass of soil invertebrates, and their distribution in soil, were surveyed largely by hand sorting and also using Tullgren and Baermann apparatuses. The densities of soil macroinvertebrates were 10²–10³ individuals/m². Diplopoda was the most abundant among them, 87.3% of which was the train millipede. The total biomass in wet weight of soil macro-invertebrates was 34.9–70.5g/m² in 1980–1981, when the millipede was pre-adult or adult, and it decreased to 3.5–6.7g/m² in 1982–1984, when it was young. The density of soil invertebrates extracted by apparatuses was 10⁴–10⁶ individuals/m². The total biomass of these was estimated to be 5.8–10.8g/m². The majority of soil invertebrates lived in the A₀ horizon, whereas the train millipede lived in soil of the A₁+A₂ horizon. These results suggest that the train millipede is one of the most important soil invertebrates affecting soil properties. For evaluating the importance of the species, more than 8 years survey of hand-sorting together with the Tullgren apparatus was necessary, as the train millipede grew synchronously and had an 8-year life span and young stages of 1.5–3.5mm long.