Toxicity assessment of microplastics within the Loire River in the clam Corbicula fluminea exposed to environmentally relevant exposure conditions.

The dispersed pollution caused by microplastics (MPs) represents a current and global concern. While the fragmentation of plastic debris into smaller particles occurs in rivers, little MP research is done on freshwater species and is published compared to the marine environment. The Loire River is the longest river in France and is subject to moderate to high anthropic pressure while it represents major societal and economic issues. However, there are not many studies that have been put forward with regards to the effect of environmental MPs (EMPs) on aquatic organisms and no policies have been enacted to monitor the plastic pollution. In this study, freshwater bivalves, Corbicula fluminea, were exposed for 21 days to environmentally relevant concentrations of a mixture of <200 µm MPs generated from plastic litter collected directly along the banks of the Loire River. This mixture was composed of 40% polyethylene (PE), 40% polypropylene (PP), 10% polyethylene terephthalate (PET) and 10% polyvinylchloride (PVC) (mass percentage). Ecotoxicological effects were assessed from the individual to the molecular levels on several endpoints: condition index, filtration efficiency, enzyme activities, lipid peroxidation, energy reserves and gene expression. The ingestion of EMPs caused damages at the biochemical level. Indeed, we reported an increase in catalase activity in gills and digestive mass, a decrease in TBARs in gills, a decrease in acetylcholinesterase activity in the digestive mass, a decrease of glycogen and lipid contents in the whole organisms and a significant induction of the expression of gst, cat, mp, acp genes. The current results suggest therefore that long-term exposure to realistic doses of EMPs causes toxicity towards freshwater benthic biota. The analysis of biomarker activities and the analysis of gene expression are complementary to prevent the effects of a plastic contamination at higher biological levels in aquatic organisms.

Adaptive changes in energy reserves and effects of body melanization on thermal tolerance in Drosophila simulans.

Seasonally polyphenic types have been documented in many Drosophilids, which differ significantly during thermal stress. Although Drosophila simulans is a sibling species to Drosophila melanogaster, both thrive in the temperate and tropical climates, but various climatic factors are expected to impact their distribution and abundance. As a result, D. simulans may use phenotypic plasticity to adapt to colder and drier circumstances in temperate zones, although such studies are less known. In the present study, our main aim was to find a link between adaptive plasticity and thermal tolerance in D. simulans. We characterized two morphs in D. simulans flies based on the abdominal melanization collected from the same locality and season, as this trait is highly associated with the larval developmental conditions. Our results suggested that flies reared from dark and light morph showed significant differences in the basal level of proline, carbohydrates (trehalose, glycogen), and lipids (cuticular lipids and total body lipids) within simulated seasons and morph lineages in D. simulans flies. We further showed that D. simulans reared from dark morph are better adapted to cold conditions, whereas light flies are more adapted to warm conditions. The flies, both from light and dark morph lineages, when reared at 15 °C, showed an increase in the level of total body lipids after acclimation at 0 °C but a decrease in the level of proline and carbohydrates (trehalose, glycogen). Heat acclimation increases glycogen levels in the flies from light morph lineage while decreases trehalose and proline.

Physiological and biochemical response of the solitary bee Osmia bicornis exposed to three insecticide-based agrochemicals.

The physiological and biochemical stress induced by pesticides need to be addressed in economically and ecologically important non-Apis solitary bees, particularly at lower than field-applied concentrations. Thus, the aim of the present study was to analyse the physiological and biochemical changes in female adult Osmia bicornis bees upon continuous oral exposure to three insecticide-based agrochemicals - i.e. Dursban 480 EC (active ingredient - a.i. chlorpyrifos), Sherpa 100 EC (a.i. cypermethrin), and Mospilan 20 SP (a.i. acetamiprid), in a toxicokinetic manner (feeding with either insecticide-contaminated food or uncontaminated food (controls) for 8 d in the contamination phase followed by 8 d of decontamination (i.e. feeding with uncontaminated food)). All three tested agrochemicals altered the energetic budget of bees by the deprivation of energy derived from lipids and carbohydrates (but not proteins) and/or a decrease in respiration based metabolic rate (energy consumption) compared to the controls. The activities of acetylcholinesterase and glutathione-S-transferase enzymes were not altered by insecticides at tested concentrations. These results show that chronic exposure to at least some pesticides even at relatively low concentrations may cause severe physiological disruptions that could potentially be damaging for the solitary bees.

Mortality, energy reserves, and oxidative stress responses of three native freshwater mussels to temperature as an indicator of potential impacts of climate change: A laboratory experimental approach.

Due to rapid global climate change, the temperature of streams and rivers is predicted to be increased, influencing aquatic organisms, particularly bivalve species. To better understand their response to elevated temperature, three native species of freshwater mussels namely, Coelatura aegyptiaca, Mutela rostrata and Chambardia rubens were exposed for 21 days to four temperature treatments (18 - 25-30 and 35 °C). Mortality was recorded on a daily basis over the experiment. A variety of responses including biomarkers at the cellular level and whole organism level were examined in surviving organisms after 21 days. In response to exposure to thermal stress, three mussel species exposed to 35 °C showed 100% mortality after 21 days. However, exposure to 25 °C and 30 °C induced significant decreases in adenosine triphosphate (ATP) production and energy reserves (Protein, lipid and glycogen) compared to the control group maintained at 18 °C. Temperature-induced oxidative stress, indicated by the greatest reduction in total antioxidant capacity (TAC) and elevated levels of lipid peroxidation products. As energy generation decreased and oxidative stress increased, trends were for condition indexes (CI) and survival to decrease. In comparison, C. rubens has a higher thermal tolerance than C. aegyptiaca, and M. rostrata. The responses reported herein, along with the predicted rates of climate warming, indicated that freshwater mussels in the Nile River, Egypt will be negatively impacted by climate change and may incur significant losses in the coming years.

Biological toxicity of Ruta graveolens essential oil against three species of diptera Drosophila melanogaster, Culex pipiens and Culiseta longiareolata.

BACKGROUND & OBJECTIVES: Recently, the use of biodegradable and environment friendly plant-based bioinsecticides has received a great deal of attention from researchers to control insect disease vectors. The aim of this research is to determine the larvicidal efficacy of Ruta graveolens essential oil against third instar larvae of two species of mosquito (Culex pipiens and Culiseta longiareolata) and a biological model Drosophila melanogaster. METHODS: Culiseta longiareolata and Culex pipiens larvae were collected from untreated areas located in Tebessa and Drosophila melanogaster, the wild strain collected from rotten apples in the Tebessa region. Ruta graveolens essential oil has been tested at different concentrations between 2.5µ/mL and 140µL/mL against third instar larvae of the three species under standard laboratory conditions according to the recommendations from the Word Health Organization. The effects were examined on mortality, growth and the main components (proteins, carbohydrates, lipids). RESULTS: The essential oil showed larvicidal activity with LC50 and LC90 values (10.85µL/mL, 70.95µL/mL and 39.4µL/mL), (26µL/mL, 144.5µL/mL and 89.57µL/mL) against third instar larvae of Drosophila melanogaster, Culex pipiens and Culiseta longiareolata respectively. In addition, it disrupted the growth and several morphological malformations were observed. It also affected growth and the main components (proteins, carbohydrates, lipids). INTERPRETATION & CONCLUSION: The essential oil affected growth and energy reserves for all three species. The results indicated that the essential oil of Ruta graveolens has good potential as a source of natural larvicides.

Insights into the ecotoxicological perturbations induced by the biocide Abamectin in the white snail, Theba pisana.

Abamectin (avermectin B1, ABM) has been widely used as a biocide in agriculture, veterinary and medicine around the world. Yet, there is still a lack of knowledge about the ecotoxicological effects of ABM. In this study, we investigated the acute toxicity and sub-lethal (20% and 60% LD50) biochemical responses of ABM on the non-target land snail, Theba pisana. Mortality of snails increased with the dose increase, resulting 48 h- LD50 value of 1.048 µg/snail. The biochemical results showed a decrease in glycogen content and lipids for two sub-lethal doses after all time intervals, whereas increased the level of total proteins after exposure to 60% LD50 ABM. Overall, the tested sub-lethal doses significantly decreased the total energy reserves. ABM-exposure to snails elevated γ-Glutamyl transferase and Lactate dehydrogenase activities at all-time intervals. A significant increase of Glutathione-S-transferase activity was also recorded in snails exposed to 20% and 60% LD50 after 7 days and all time intervals, respectively. However, ABM inhibited the activity of Aspartate aminotransferase and Alanine aminotransferase after 7 days of exposure. Our investigation provides new insights into the disturbances of energy reserves and enzyme activities in T. pisana that are sensitive and may be used as biomarkers for assessing ABM toxicity.

Three questions about the eco-physiology of overwintering underground.

In cold environments ectotherms can be dormant underground for long periods. In 1941 Cowles proposed an ecological trade-off involving the depth at which ectotherms overwintered: on warm days, only shallow reptiles could detect warming soils and become active; but on cold days, they risked freezing. Cowles discovered that most reptiles at a desert site overwintered at shallow depths. To extend his study, we compiled hourly soil temperatures (5 depths, 90 sites, continental USA) and physiological data, and simulated consequences of overwintering at fixed depths. In warm localities shallow ectotherms have lowest energy costs and largest reserves in spring, but in cold localities, they risk freezing. Ectotherms shifting hourly to the coldest depth potentially reduce energy expenses, but paradoxically sometimes have higher expenses than those at fixed depths. Biophysical simulations for a desert site predict that shallow ectotherms have increased opportunities for mid-winter activity but need to move deep to digest captured food. Our simulations generate testable predictions to eco-physiological questions but rely on physiological responses to acute cold rather than to natural cooling profiles. Furthermore, natural-history data to test most predictions do not exist. Thus, our simulation approach uncovers knowledge gaps and suggests research agendas for studying ectotherms overwintering underground.

Plasticity of nutrient accumulation patterns in diapausing fall webworm pupae.

The accumulation of nutrients during diapause preparation is crucial because any lack of nutrition will reduce the likelihood of insects completing diapause, thereby decreasing their chances of survival and reproduction. The fall webworm, Hyphantria cunea, diapause as overwintering pupae and their diapause incidence and diapause intensity are regulated by the photoperiod. In this study, we test the hypothesis that photoperiod influences energy reserve accumulation during diapause preparation in fall webworm. We found that the body size and mass, lipid and carbohydrate content of pupae with a short photoperiod during the diapause induction phase were significantly greater than those of pupae with a relatively short photoperiod, and the efficiency of converting digested food and ingested food into body matter was greater in the short-photoperiod diapause-destined larvae than the relatively short-photoperiod diapause-destined larvae. We also observed higher lipase and amylase activities in short-photoperiod diapause-destined larvae relative to the counterparts. However, no obvious difference was found in protein and protease in the pupae with a short photoperiod during the diapause induction phase and short-photoperiod diapause-destined larvae compared with the counterparts. Therefore, we conclude that the energy reserve patterns of diapausing fall webworm pupae are plastic and that short-photoperiod diapause-destined larvae increase their energy reserves by improving their feeding efficiency and increase their lipid and carbohydrate stores by increasing the lipase and amylase activities in the midgut.

Do energy reserves and cold hardiness limit winter survival of Culex pipiens?

The risks of depletion of energy reserves and encountering lethally low temperatures are considered as two important mortality factors that may limit winter survival of mosquito, Culex pipiens f. pipiens populations. Here we show that the autumn females carry lipid reserves, which are safely sufficient for at least two overwintering periods, provided the females diapausing at temperatures typical for underground spaces (0 °C - 8 °C) would continuously rest at a standard metabolic rate (SMR). The overwintering females, however, switch from SMR to much higher metabolic rate during flight, either seeking for optimal microhabitat within the shelter or in response to disturbances by air current or predator attack. These behaviors result in fast oxidation of lipid reserves and, therefore, the autumn load of energy reserves may actually limit winter survival under specific circumstances. Next, we show that the level of females' cold hardiness is physiologically set relatively weak for overwintering in open field, above-ground habitats, but is ecologically entirely sufficient for overwintering in most underground spaces. The characteristics of suitable overwintering shelters are: no or limited risk of contact with ice crystals, no or limited air movements, winter temperatures relatively stable between +2 and + 6 °C, winter minimum does not drop below -4 °C for longer than one week, or below -8 °C for longer than 1 day.

Direct and size-mediated effects of temperature and ration-dependent growth rates on energy reserves in juvenile anadromous alewives (Alosa pseudoharengus).

Growth rate and energy reserves are important determinants of fitness and are governed by endogenous and exogenous factors. Thus, examining the influence of individual and multiple stressors on growth and energy reserves can help estimate population health under current and future conditions. In young anadromous fishes, freshwater habitat quality determines physiological state and fitness of juveniles emigrating to marine habitats. In this study, the authors tested how temperature and food availability affect survival, growth and energy reserves in juvenile anadromous alewives (Alosa pseudoharengus), a forage fish distributed along the eastern North American continent. Field-collected juvenile anadromous A. pseudoharengus were exposed for 21 days to one of two temperatures (21°C and 25°C) and one of two levels of food rations (1% or 2% tank biomass daily) and compared for differences in final size, fat mass-at-length, lean mass-at-length and energy density. Increased temperature and reduced ration both led to lower growth rates, and the effect of reduced ration was greater at higher temperature. Fat mass-at-length decreased with dry mass, and energy density increased with total length, suggesting size-based endogenous influences on energy reserves. Lower ration also directly decreased fat mass-at-length, lean mass-at-length and energy density. Given the fitness implications of size and energy reserves, temperature and food availability should be considered important indicators of nursery habitat quality and incorporated in A. pseudoharengus life-history models to improve forecasting of population health under climate change.

Understanding the early ontogenetic stages of Mugil liza (Mugilidae): Morphological traits and digestive/metabolic profile of pre-juveniles after recruitment.

The family Mugilidae consists mainly of diadromous species, whose reproduction occurs in offshore waters. Pre-juveniles shift their diet in the surf zone (zooplanktophagous to iliophagous). Later, during their recruitment into estuaries, huge changes take place in their digestive system. However, digestive and metabolic characteristics and some morphological traits at recruitment are unknown for Mugilidae. We performed comparative studies on early and late pre-juveniles of Mugil liza recruited in Mar Chiquita Coastal Lagoon (37°32'-37°45'S, 57°19'-57°26'W, Argentina). We determined digestive enzyme activities (intestine), energy reserves (liver/muscle), total/standard length, total weight, intestinal coefficient, hepatosomatic index and retroperitoneal fat. Pre-juveniles exhibited amylase, maltase, sucrase, lipase, trypsin and aminopeptidase-N (APN) activities, which were maintained over a wide range of pH and temperature, and exhibited Michaelis-Menten kinetics. In late pre-juveniles, amylase (422 ± 131 µmol maltose min-1 mgprot-1 ), sucrase (86 ± 14 mg glucose min-1 mgprot-1 ), trypsin (84 ± 9 µmoles min-1 mgprot-1 ) and APN (0.58 ± 0.08 µmoles min-1 mgprot-1 ) activities were higher (42%, 28%, 35% and 28%, respectively) than in the early stage. Also, the intestinal coefficient was higher in late (3.04) compared to early (2.06) pre-juveniles. Moreover, the liver appeared to be a main site of glycogen and triglyceride storage in late pre-juveniles, muscle being the site of storage in early pre-juveniles, exhibiting higher glycogen, free glucose and protein concentrations (92%, 82%, 32%, respectively). The results suggest that pre-juveniles of M. liza exhibit an adequate digestive battery to perform complete hydrolysis of various dietary substrates, availability of energy reserves and morphological characteristics to support their feeding habit and growth after recruitment. Our results represent an important contribution to knowledge of the ecology and digestive physiology of pre-juveniles of Mugilidae in the wild.

Hypoxia-seeking behavior, metabolic depression and skeletal muscle function in an amphibious fish out of water.

Several animals enter a state of dormancy to survive harsh environmental conditions. During dormancy, metabolic depression can be critical for economizing on limited endogenous energy reserves. We used two isogenic strains (strain 1 and strain 2) of a self-fertilizing amphibious fish (Kryptolebias marmoratus) to test the hypothesis that animals seek hypoxic microhabitats that, in turn, accentuate metabolic depression during dormancy. Using custom-built tunnels that maintained a longitudinal O2 gradient (hypoxic to normoxic), we assessed the O2 preference of K. marmoratus during prolonged air exposure. In support of our hypothesis, we found that one isogenic strain (strain 2) spent more time in hypoxia compared with normoxia after 21 days in air. Prolonged air exposure in both strains resulted in lower O2 consumption rates compared with active fish (35% depression), which was accentuated (51% depression) when fish were exposed to aerial hypoxia acutely. We then tested the hypothesis that chronic aerial hypoxia acclimation would protect endogenous energy reserves and skeletal muscle integrity, thereby maintaining locomotor performance, possibly owing to hypoxic hypometabolism. We found that air-acclimated fish from both strains were in poorer body condition relative to fish acclimated to aerial hypoxia. Furthermore, aerial hypoxia acclimation minimized glycogen usage (strain 1), lipid catabolism (strain 2) and white muscle atrophy (strain 2), as well as preserved terrestrial locomotor performance compared with fish in air (strain 2). Overall, our findings suggest that some K. marmoratus strains seek microhabitats that accentuate metabolic depression during dormancy, and that microhabitat O2 availability may have significant implications for energy metabolism, and the structure and function of skeletal muscle. Furthermore, the differential responses between isogenic strains suggests that genetic factors also contribute to phenotypic differences in the emersion behavior and physiology of this species.

Variation in outer blubber lipid concentration does not reflect morphological body condition in humpback whales.

An animal's body condition provides valuable information for ecophysiological studies, and is an important measure of fitness in population monitoring and conservation. While both the external body shape of an animal and its internal tissues (i.e. fat content) can be used as a measure of body condition, the relationship between the two is not always linear. We compared the morphological body condition (external metric obtained through aerial photogrammetry) of migrating humpback whales (Megaptera novaeangliae) with their outer blubber lipid concentration (internal metric obtained through blubber biopsy sampling) off the coast of south-west Australia early and late in the breeding season (spanning ∼4.5 months). The external body condition index of juvenile and adult humpback whales decreased by 26.9 (from 18.8% to -8.1%) and 12.0 percentage points (from 8.6% to -3.4%), respectively, between the early and late phase. In contrast, we found no intra-seasonal change in blubber lipid concentration, and no difference between reproductive classes (juveniles, adults and lactating females); however, the small sample size prevented us from effectively testing these effects. Importantly, however, in the 33 animals for which paired metrics were obtained, we found no correlation between the morphometric body condition index and the blubber lipid concentration of individual whales. The lack of a linear relationship suggests that changes in outer blubber lipid concentration do not reflect external changes in body shape, thus limiting the utility of outer blubber lipid reserves for individual body condition evaluation. The wider spectrum of change in body morphometry captured with aerial photogrammetry supports the use of body morphometry as a reliable and well-tested method.

Effects of a glyphosate-based herbicide on the development and biochemical biomarkers of the freshwater copepod Notodiaptomus carteri (Lowndes, 1934).

In this work we analyzed the effects of Sulfosato Touchdown®, a glyphosate-based herbicide, on the ontogenic development and biochemical markers of the freshwater copepod Notodiaptomus carteri. A 30-days life-cycle experiment was carried out with three different glyphosate concentrations (0, 0.38, and 0.81 mg L-1) to analyze the developmental time from nauplii to adult copepods and their individual growth. An additional 10-days experiment with the same glyphosate concentrations was designed to evaluate the energy reserves (glycogen, proteins and lipids) and the activity of three antioxidant enzymes, superoxide dismutase (SOD), catalase, and glutathione-S-transferase (GST) in adult copepods, separately for females and males. We found that the lowest glyphosate concentration increased the nauplii and total development time. The highest glyphosate concentration prevented copepods from reaching the adult stage, inhibited the growth of the first copepodite stage and increased the GST and SOD activity in adult females. According to our results, the presence of this herbicide in freshwater systems could impose a risk in the ecological role of copepods in nature. This study will contribute to propose the Notodiaptomus genus as model specie for monitoring purposes in the Neotropical aquatic systems.

Effects of abamectin-based and difenoconazole-based formulations and their mixtures in Daphnia magna: a multiple endpoint approach.

This study evaluated the toxicity of pesticide formulations Kraft® 36 EC (active ingredient-a.i. abamectin) and Score® 250 EC (a.i. difenoconazole), and their mixtures in Daphnia magna at different biological levels of organization. Survival, reproduction and biochemical markers (cholinesterase (ChE), catalase (CAT) and lipid peroxidation (LPO)) were some of the endpoints evaluated. Total proteins and lipids were also studied together with energy consumption (Ec). D. magna neonates were exposed for 96 h to Kraft (2, 4, and 6 ng a.i./L) and Score (12.5, 25, and 50 µg a.i./L) for the biochemical experiments, and for 15 days to abamectin (1-5 ng a.i./L) and to difenoconazole (3.12-50 µg a.i./L) to assess possible changes in reproduction. Exposures of organisms to both single compounds did not cause effects to antioxidant and detoxifying enzymes, except for LPO occurring at the highest concentration of difenoconazole tested. For ChE and CAT there was enzymatic induction in mixture treatments organisms, occurring at minor pesticides concentrations for CAT and at the two highest concentrations for ChE. There were no significant differences for total protein in D. magna but lipids showed an increase at the highest concentrations of pesticide mixture combinations. There was a significant increase of Ec in individuals of all treatments tested. In the chronic test, increased fecundity occurred for D. magna under difenoconazole exposures and mixtures. This study demonstrated that mixtures of these pesticides caused greater toxicity to D. magna than when tested individually, except for Ec. Therefore, effects of mixtures are very hard to predict only based on information from single compounds, which most possibly is the result of biological complexity and redundancy in response pathways, which need further experimentation to become better known.

Physiological responses of plants and mites to salicylic acid improve the efficacy of spirodiclofen for controlling Tetranychus urticae (Acari: Tetranychidae) on greenhouse tomatoes.

Salicylic acid (SA) is a signaling molecule that can induce plant resistance to certain herbivores. Although the role of jasmonic acid in mediating mite-tomato plant interactions has been well studied, the role of salicylic acid has not. This study examined how the application of exogenous SA, via its effects on tomato plant physiology, alters the activity of mite digestive enzymes, mite energy reserves, and mite susceptibility to spirodiclofen. Enzymatic activity-including superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase-along with contents of total phenolic, hydrogen peroxide, and total chlorophyll significantly increased in plants 24 h after treatment with 2 mM of SA. In contrast, catalase activity significantly decreased in treated plants, and malondialdehyde content was unaffected. Mites fed on tomato plants treated with SA had significantly lower glutathione S-transferase, esterase, α-amylase, and aminopeptidase activities than those fed on control plants. Energy reserve analyses demonstrated a significant decrease in contents of lipid, protein, and glycogen in mites fed on SA-treated plants, whereas carbohydrate content significantly increased. The LC50 of spirodiclofen was decreased 1.8-fold for Tetranychus urticae fed on SA-treated tomato plants compared to controls. Treatment of adult mites with 2 mM SA on leaf discs did not cause any direct mortality after 24 h. Finally, a greenhouse bioassay confirmed that spider mite mortality following exposure to spirodiclofen was significantly higher on SA plants than on control plants. Mortality of mites exposed to half of the recommended rate of spirodiclofen was similar to those exposed to the recommended rate when they were held on treated plants. These results have valuable implications for T. urticae management programs in tomato production.

Progressive behavioural, physiological and transcriptomic shifts over the course of prolonged starvation in ticks.

Ticks are obligatorily hematophagous but spend the majority of their lives off host in an unfed state where they must resist starvation between bouts of blood feeding. Survival during these extended off-host periods is critical to the success of these arthropods as vectors of disease; however, little is known about the underlying physiological and molecular mechanisms of starvation tolerance in ticks. We examined the bioenergetic, transcriptomic and behavioural changes of female American dog ticks, Dermacentor variabilis, throughout starvation (up to nine months post-bloodmeal). As starvation progressed, ticks utilized glycogen and lipid, and later protein as energy reserves with proteolysis and autophagy facilitating the mobilization of endogenous nutrients. The metabolic rate of the ticks was expectedly low, but showed a slight increase as starvation progressed possibly reflecting the upregulation of several energetically costly processes such as transcription/translation and/or increases in host-seeking behaviours. Starved ticks had higher activity levels, increased questing behaviour and augmented expression of genes related to chemosensing, immunity and salivary gland proteins. The shifts in gene expression and associated behavioural and physiological processes are critical to allowing these parasites to exploit their ecological niche as extreme sit-and-wait parasites. The overall responses of ticks to starvation were similar to other blood-feeding arthropods, but we identified unique responses that could have epidemiological and ecological significance for ticks as ectoparasites that must be tolerant of sporadic feeding.

In ovo feeding of creatine pyruvate alters energy metabolism in muscle of embryos and post-hatch broilers.

OBJECTIVE: This study was conducted to investigate the effects of in ovo feeding (IOF) of creatine pyruvate (CrPyr) on the energy metabolism in thigh muscle of embryos and neonatal broilers. METHODS: A total of 960 eggs were randomly assigned to three treatments: i) non-injected control group, ii) saline group injected with 0.6 mL of physiological saline (0.75%), and iii) CrPyr group injected with 0.6 mL of physiologi-cal saline (0.75%) containing 12 mg CrPyr/egg on 17.5 d of incubation. After hatching, 120 male chicks (close to the average body weight of the pooled group) in each group were randomly assigned to eight replications. The feeding experiment lasted 7 days. RESULTS: The results showed that IOF of CrPyr increased glucose concentrations in the thigh muscle of broilers on 2 d after injection (p<0.05). Compared with the control and saline groups, the concentration of creatine in CrPyr group was increased on 2 d after injection and the day of hatch (p<0.05). Moreover, IOF of CrPyr increased the creatine kinase activity at hatch and increased the activities of hexokinase and pyruvate kinase on 2 d after injection and the day of hatch (p<0.05). Chicks in CrPyr group showed higher mRNA expressions of glucose transporter 3 (GLUT3) and GLUT8 on the day of hatch (p<0.05). CONCLUSION: These results demonstrated that IOF of CrPyr was beneficial to enhance muscle energy reserves of em-bryos and hatchlings.

Effects of mechanical disturbance and salinity stress on bioenergetics and burrowing behavior of the soft-shell clam Mya arenaria.

Bioturbation of sediments by burrowing organisms plays a key role in the functioning of coastal ecosystems. Burrowing is considered an energetically expensive activity, yet the energy costs of burrowing and the potential impacts of multiple stressors (such as salinity stress and wave action) on bioenergetics and burrowing performance of marine bioturbators are not well understood. We investigated the effects of mechanical disturbance and salinity stress on the burrowing behavior, aerobic capacity and energy expense of digging in a common marine bioturbator, the soft-shell clam Mya arenaria from the Baltic Sea (control salinity 15). Mya arenaria showed large individual variability in the burrowing efficiency, with an average of ∼7% of the body energy reserves used per burial. Clams with higher mitochondrial capacity and lower energy expenditure per burial showed higher endurance. Acclimation for 3-4 weeks to low (5) or fluctuating (5-15) salinity reduced the burrowing speed and the number of times the clams can rebury but did not affect the mitochondrial capacity of the whole body or the gill. Acclimation to the fluctuating salinity shifted the predominant fuel use for burrowing from proteins to lipids. Our data indicate that the reduced burrowing performance of clams under the salinity stress is not due to the limitations of energy availability or aerobic capacity but must involve other mechanisms (such as impaired muscle performance). The reduction in the burrowing capacity of clams due to salinity stress may have important implications for survival, activity and ecological functions of the clams in shallow coastal ecosystems.

Optimal gut size of small birds and its dependence on environmental and physiological parameters.

Most optimal foraging models assume that the foraging behaviour of small birds depends on a single state variable, their energy reserves in the form of stored fat. Here, we include a second state variable-the contents of the bird's gut-to investigate how a bird should optimise its gut size to minimise its long-term mortality, depending on the availability of food, the size of meal and the bird's digestive constraints. Our results show that (1) the current level of fat is never less important than gut contents in determining the bird's survival; (2) there exists a unique optimal gut size, which is determined by a trade-off between the energetic gains and costs of maintaining a large digestive system; (3) the optimal gut size increases as the bird's digestive cycle becomes slower, allowing the bird to store undigested food; (4) the critical environmental factor for determining the optimal gut size is the mass of food found in a successful foraging effort ("meal size"). We find that when the environment is harsh, it is optimal for the bird to maintain a gut that is larger than the size of a meal. However, the optimal size of the gut in rich environments exactly matches the meal size (i.e. the mass of food that the optimal gut can carry is exactly the mass of food that can be obtained in a successful foraging attempt).