Growth and haematological response of sturgeon hybrids Russian sturgeon (Acipenser guldenstadti brandt) × beluga (Huso huso L.) to protein and lipid contents in the diet

• 1.1. Fingerlings of intergenious hybrid Russian sturgeon (Acipenser guldenstadti) × beluga (Huso huso) weighing 22 g reared in water with salinity 18 ppt were fed nine diets differing in protein and fat content.
• 2.2. The increase of dietary protein content (from 45 to 52%) improved the fingerlings growth rate, food and protein conversion efficiencies. No effect of further protein content increase to 60% was observed.
• 3.3. The increase of dietary fat content from 10 to 20% positively influenced all growth results.
• 4.4. The muscular lipid content increased following the increase in dietary fat due to accumulation of triacylglycerols.
• 5.5. Distinctive leucopenia in neutrophils and leucophilia in lymphocytes following dietary protein and fat content increase were observed.
• 6.6. It was concluded that within the analysed range of values the increase of dietary protein and lipid content improved the physiological status of sturgeon hybrid fingerlings.

     

Does the pressor response to ischemic exercise improve blood flow to contracting muscles in humans?

The purpose of this study was to determine in humans 1) the gain for the reflex pressor response that occurs when perfusion pressure to rhythmically contracting muscles is reduced and 2) whether the pressor response improves blood flow to the contracting muscles. Six normal subjects performed light, moderate, and heavy rhythmic forearm contractions (30/min) with the forearm enclosed in a Plexiglas box. Pressure in the box was increased 10 mmHg each minute up to 50 mmHg to reduce transmural pressure in the arterial system of the forearm. Mean arterial pressure (MAP) was measured continuously. During light exercise no reflex increase in MAP occurred until box pressure was 50 mmHg. During moderate and heavy exercise MAP began to increase with only 10- to 20-mmHg increases in box pressure. The slope of this increase was 3.5-3.9 mmHg per 10 mmHg of box pressure (approximately 60% of that in dogs). In a further study on six subjects a deep vein draining the active forearm muscles was cannulated and deep venous O2 saturation measured to assess how a 50-mmHg increase in box pressure and subsequent reflex increase in MAP altered blood flow to the contracting muscles during heavy rhythmic exercise. The increase in box pressure reduced blood flow to contracting forearm muscles by 20-25% and was followed by a 19-mmHg increase in MAP that did not appear to improve perfusion of the active muscles. This finding was unexpected, because studies in dogs suggest that the pressor response to rhythmic exercise with restricted muscle blood flow can improve perfusion of the active muscles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Does the type of exercise affect tryptophan catabolism in horses?

Tryptophan (Trp) is an essential amino acid which metabolises via the kynurenine pathway to generate a number of bioactive substances referred to as kynurenines. Among those are 3-hydroxykynurenine (3-HKyn) and quinolinic acid, which are neurotoxic, as well as kynurenic acid (Kyna) and xanthurenic acid (XA), which, similarly to nicotinamide (NAm), show neuroprotective and anti-depressive effects. Routine exercise is known to modulate Trp metabolism in skeletal muscle and is thus believed to reduce the risk of depressive states in humans and laboratory animals. Analogously, it was hypothesised that exercise can influence Trp metabolism in horses as well. The aim of this study was to evaluate the influence of two different types of exercise on Trp metabolism in horses of the same breed. A total of 32 purebred Arabian horses were involved in the study. The 22 three-year-old racehorses were subjected to short-time intense exercise. Ten other horses were made to perform endurance competitions at a distance of 80 km. Blood samples were collected at rest and following the end of the exercise period. Plasma concentrations of Trp, kynurenine (Kyn), Kyna, 3-HKyn, XA and NAm were determined using Ultra-High Performance Liquid Chromatography-Electrospray Ionisation-Tandem Mass Spectrometry. Short-time intense exercise led to an increase in plasma concentrations of Kyn, Kyna and XA. The endurance effort induced an increase in Kyna and a decrease in Trp and NAm levels. Both types of exercise, short-time intensive exercise and endurance exercise induced an increase in Trp metabolites, especially Kyna, and did not induce an increase in Trp level. Thus, from a pathophysiological perspective of the kynurenine pathway’s influence on mental state, both types of exercise induced beneficial effects in horses.     

Does access to open water affect the behaviour of Pekin ducks (Anas platyrhynchos)?

Ducks show a wide range of water-related behaviours but commercial production often involves access to water that allows drinking only. In this study we evaluated effects of four water resource (WR) treatments on water related behaviours of Pekin ducks. Ducks (n = 2800) were kept in one of four water provision treatments (7 replicate groups of 100 ducks per treatment) from 20 days of age: a bath that allowed full access to water; a trough in which the head could be dipped but without body access; turkey bell drinkers; chicken bell drinkers. The turkey and chicken bells provided easy access for drinking but less opportunity for interaction with the water. The behaviour of the ducks was video recorded, then analysed using scan sampling at 7.5 min intervals between 10:00 and 22:00 at 21, 32, 42 and 45 days. As might be expected, as birds grew, fewer were observed in the bath and over all treatments the amount of preening behaviour increased as ducks aged. Although ducks with access to a bath spent less time in or near the bath, this does not indicate lack of importance to the birds. Fewer ducks were observed standing or resting idle at the bath, and they performed proportionately more water-related preening behaviours than ducks in the other treatments. Moreover, as access to water increased (i.e. from beak only, through to entire body access) higher proportion of preening ducks performed head-dipping behaviour, and a lower proportion performed feather manipulation. This work shows that provision of a water resource that permits full body access appears to promote efficiency of drinking-related behaviours and preening behaviour. This helps to explain improvements in feather hygiene reported in other studies where the birds had full access to, or greater access to water.     

Does anthocyanin affect outcrossing rates in Datura Stramonium (Solanaceae)?

In this paper, I investigate whether the presence or absence of anthocyanin is neutral with respect to reproduction in Datura stramonium. The observations concern the portion of the life cycle spanning pollination to germination. Pollinators do not appear to distinguish between floral morphs, as revealed by nonbiased distribution of fluorescent powder used as a pollen analogue. Pollen-tube growth is also equal for the two morphs. Seed germination is affected by the presence of anthocyanin, but apparently only by the genotype of the mother at the anthocyanin locus, and not by the genotype of the embryo itself. In addition, there was an interaction between maternal morph and the maternal source population, with seeds from high-elevation anthocyanin-producing mothers germinating most rapidly and seeds from low-elevation anthocyanin-producing mothers germinating most slowly in a common garden at low elevation. However, because germination of anthocyanin-producing and anthocyaninless progeny proceed equally quickly, the anthocyanin marker provides unbiased estimates of outcrossing rates. The results overall support the use of anthocyanin as a neutral marker, with the alternate phenotypes unlikely to be differentially impacted by the processes of pollination, pollen-tube growth, and germination. Fluctuating selection on conditions for dormancy release may be partially responsible for the maintenance of the anthocyanin polymorphism in Datura stramonium.     

Declining body size: a third universal response to warming?

A recently documented correlate of anthropogenic climate change involves reductions in body size, the nature and scale of the pattern leading to suggestions of a third universal response to climate warming. Because body size affects thermoregulation and energetics, changing body size has implications for resilience in the face of climate change. A review of recent studies shows heterogeneity in the magnitude and direction of size responses, exposing a need for large-scale phylogenetically controlled comparative analyses of temporal size change. Integrative analyses of museum data combined with new theoretical models of size-dependent thermoregulatory and metabolic responses will increase both understanding of the underlying mechanisms and physiological consequences of size shifts and, therefore, the ability to predict the sensitivities of species to climate change.     

Can juvenile Baltic sturgeon (Acipenser oxyrinchus) smell the enemy?

Atlantic sturgeon (Acipenser oxyrinchus), also known as Baltic sturgeon, is considered extinct in German waters. Fish‐rearing for conservation purposes largely relies on classical hatchery technology focusing on traits like survival and growth in captivity but rarely focusing on subsequent life in the wild, lacking skills such as foraging or anti‐predation behavior. Predation is hence a major factor for mortality in newly stocked individuals. The aim of this study was to evaluate if naïve Baltic sturgeon juveniles were able to recognize a common predator—zander (Sander lucioperca)—by olfactory cues and adapt accordingly. Over a period of 30 days, Baltic sturgeons were supplied with effluent water from a rearing tank with zander (zander unit) and, as a control, carp (carp unit), three tanks each. Distribution within the tank, morphology of the dorsal scutes, stress (glucose, lactate and cortisol) and gene expression of brain plasticity and cognition were studied in comparison to the control group (carp unit). No significant differences between the zander and the carp unit were observed in any of the parameters measured. Thus, we conclude that naïve Baltic sturgeon is not able to innately recognize potential predators by olfaction alone. Therefore, future studies should focus on applying predator odor together with chemical alarm substances.     

Does body size influence thermal biology and diet of a python (Morelia spilota imbricata)?

Current theory predicts that larger‐bodied snakes not only consume larger prey (compared with smaller individuals), but may also have a different range of prey available to them due to their thermal biology. It has been argued that smaller individuals, with lower thermal inertia (i.e. faster cooling rates at nightfall when air temperature falls and basking opportunities are limited), may be thermally restricted to foraging and hunting during the day on diurnally active prey, and have reduced capacity to hunt crepuscular and nocturnal prey species. This predictive theory was investigated by way of dietary analysis, assessment of thermal biology and thermoregulation behaviour in an ambush forager, the south‐west carpet python (Morelia spilota imbricata, Pythonidae). Eighty‐seven scats were collected from 34 individual pythons over a 3‐year radiotelemetry monitoring study. As predicted by gape size limitation, larger pythons took larger prey; however, 65% of prey items of small pythons were represented by nocturnally active, small mammals, a larger proportion than present in larger snakes. Several measures of thermal biology (absolute body temperature, thermal differential of body temperature to air temperature, maximum hourly heating and cooling rates) were not strongly affected by python body mass. Additionally, body temperature was only influenced by the behavioural choice of microhabitat selection and was not affected by python body size or position, suggesting that these behavioural choices do not allow smaller pythons to vastly increase their temporal foraging window. By coupling dietary analysis, measures of body temperature and behavioural observations of free‐ranging animals, we conclude that, contrary to theoretical predictions, a small body size does not thermally restrict the temporal window for ambush foraging in M. s. imbricata. An ontogenetic or size‐determined switch from ambush feeding to actively foraging on slower prey would account for the differences in prey taken by these animals. The concept of altered foraging behaviour warrants further investigation in this species.     

Does background nitrogen deposition affect the response of boreal vegetation to fertilization?

Forest floor vegetation is an important component of forest biodiversity, and numerous studies have shown that N input alters the vegetation. In some cases, however, the effects of experimental N addition have been small or absent. Two alternative hypotheses have been suggested: (a) competition from the tree layer confounds the response to N, or (b) N response in areas with high background deposition is limited by N saturation. Neither of these hypotheses has so far been explicitly tested. Here, we compile data on forest floor vegetation from N addition experiments, in which the forest had been clear-cut, along an N deposition gradient ranging from 4 to 16 kg ha^?1 year^?1 in Sweden. We analyzed the effects of N addition and its interaction with N deposition on common species and thereby tested the second hypothesis in an environment without the confounding effects of the tree layer. The results show that the effects of the experimental N addition are significantly influenced by background N deposition: the N addition effects are smaller in areas with high N deposition than in areas with low N deposition, despite the fact that the highest N deposition in this study can be considered moderate from an international perspective. The results are important when assessing the reliability of results from N addition experiments on forest floor vegetation in areas with moderate to high background N deposition. We conclude that the interacting effects of N addition and N deposition need to be included when assessing long-term N sensitivity of plant communities.     

Does body size difference in the leeches Glossiphonia complanata (L.) and Helobdella stagnalis (L.) contribute to co-existence?

The effect of predator and prey body size on the feeding success of the British lake-dwelling leeches Glossiphonia complanata and Helobdella stagnalis was examined in the laboratory, and any involvement of size difference between the leeches in allowing coexistence in the field assessed. G. complanata breeds in advance of H. stagnalis and maintains a body size advantage throughout their annual life-cycle. In experiments, conducted at 14 °C and a photoperiod of 16 hrs L: 8 hrs D, three size classes of leeches of each species were each exposed to each of three size classes of each of five prey species, viz. Tubifex sp., Chironomus sp., Asellus aquaticus, Lymnaea peregra and Potamopyrgus jenkinsi. For each prey species, three different types of experiments were performed: one leech exposed to four prey individuals; four leeches of the same species with sixteen prey; and two leeches of each species with sixteen prey. In the first experiment, all sizes of G. complanata were capable of feeding on all sizes of the prey types offered; the same was true for H. stagnalis with exceptions of feeding on large A. aquaticus and large L. peregra. For both species, but especially for G. complanata, there was a trend within each size class of leech for decreasing proportions of fed leeches with increasing prey size, and within each size class of prey for an increasing proportion of fed leeches with increasing leech size; however there were several exceptions to these trends. Both leeches fed extensively on Tubifex sp. but there were significant differences in the proportions feeding on other prey types; G. complanata fed more on A. aquaticus and the two snail species, and less on Chironomus, than H. stagnalis. The effect of increasing the number of leech individuals from one to four individuals, of the same or mixed species, had little effect on the proportion of leeches which had fed. It is concluded that large G. complanata will have access to large individuals of certain prey taxa denied H. stagnalis, which may lessen the intensity of interspecific competition.     

Does nitrogen supply affect the response of wheat (Triticum aestivum cv. Hanno) to the combination of elevated CO(2) and O(3)?

Spring wheat (Triticum aestivum cv. Hanno) was grown at ambient (350 micromol mol(-1)) or elevated CO(2) (700 micromol mol(-1)) in charcoal/Purafil-filtered air (CFA <5 nmol mol(-1)) or ozone (CFA +75 nmol mol(-1) 7 h d(-1)) at three levels of N supply (1.5, 4 and 14 mM NO(-3)), to test the hypothesis that the combined impacts of elevated CO(2) and O(3) on plant growth and photosynthetic capacity are affected by nitrogen availability. Shifts in foliar N content reflected the level of N supplied, and the growth stimulation induced by elevated CO(2) was dependent on the level of N supply. At 60 d after transfer (DAT), elevated CO(2) was found to increase total biomass by 44%, 29%, 12% in plants supplied with 14, 4 and 1.5 mM NO(-3), respectively, and there was no evidence of photosynthetic acclimation to elevated CO(2) across N treatments; the maximum in vivo rate of Rubisco carboxylation (V(cmax)) was similar in plants raised at elevated and ambient CO(2). At 60 DAT, ozone exposure was found to suppress plant relative growth rate (RGR) and net photosynthesis (A) in plants supplied with 14 and 4 mM NO(-3). However, O(3) had no effect on the RGR of plants supplied with 1.5 mM NO(-3) and this effect was accompanied by a reduced impact of the pollutant on A. Elevated CO(2) counteracted the detrimental effects of O(3) (i.e. the same ozone concentration that depressed RGR and A at ambient CO(2) resulted in no significant effects when plants were raised at elevated CO(2)) at all levels of N supply and the effect was associated with a decline in O(3) uptake at the leaf level.     

Does smoking affect body weight and obesity in China?

An inverse relationship between smoking and body weight has been documented in the medical literature, but the effect of cigarette smoking on obesity remains inconclusive. In addition, the evidence is mixed on whether rising obesity rates are an unintended consequence of successful anti-smoking policies. This study re-examines these relationships using data from China, the largest consumer and manufacturer of tobacco in the world that is also experiencing a steady rise in obesity rates. We focus on the impact of the total number of cigarettes smoked per day on individuals’ body mass index (BMI) and on the likelihood of being overweight and obese. Instrumental variables estimation is used to correct for the endogeneity of cigarette smoking. We find a moderate negative and significant relationship between cigarette smoking and BMI. Smoking is also negatively related to being overweight and obese, but the marginal effects are small and statistically insignificant for being obese. Quantile regression analyses reveal that the association between smoking and BMI is quite weak among subjects whose BMIs are at the high end of the distribution but are considerably stronger among subjects in the healthy weight range. Ordered probit regression analyses also confirm these findings. Our results thus reconcile an inverse average effect of smoking on body weight with the absence of any significant effect on obesity. From a policy perspective these findings suggest that, while smoking cessation may lead to moderate weight gain among subjects of healthy weight, the effects on obese subjects are modest and should not be expected to lead to a large increase in obesity prevalence rates.     

Does a relationship exist between the urate pool in the body and lipid peroxidation during exercise?

In this study, we investigated whether a relationship exists between the levels of urate in vivo and lipid peroxidation during exercise. Seven healthy male subjects performed exhaustive cycling exercise under the following three conditions. The levels of urate, thiobarbituric acid reactive substances (TBARS) and allantoin in plasma and urine were examined before exercise and during a 3h recovery period. (1) Benzbromarone administration experiment: benzbromarone (an uricosuric agent) was administered orally the day before exercise. (2) IMP administration experiment: inosine 5'-monophosphate disodium salt (a precursor of urate) was administered orally the day before exercise. (3) Control experiment: no test substance was administered. The main results obtained were as follows. Plasma urate levels and total peroxyl radical-trapping antioxidant parameter (TRAP) for deproteinized plasma in the resting period significantly decreased depending on the treatment, in the order of IMP> control > benzbromarone. A significant positive correlation was evident between plasma urate levels and TRAP values for deproteinized plasma. The increase in plasma levels of allantoin was observed only in the case of IMP treatment. A significant negative correlation between plasma levels of urate in the resting period and the amounts of urinary TBARS excreted during the recovery period was recognized. These results suggest that the urate level in vivo before exercise is a factor influencing lipid peroxidation during exhaustive exercise. Furthermore, these findings support the view that urate may serve as an important freeradical scavenger in vivo.     

Does feeding on Bt-maize affect the slug Arion vulgaris (Mollusca: Arionidae)?

Via expression of Cry-proteins, toxic for specific insect groups, genetically modified Bacillus thuringiensis (Bt) maize offers an effective protection against insect pests. In a laboratory experiment with two transgenic and two non-transgenic maize varieties, a potential impact of Bt-maize was examined for the non-target slug Arion vulgaris. Lifetime after field collection, weight change and oviposition was examined for slugs fed with Bt-maize, non Bt-maize or dandelion (Taraxacum officinale). Test parameters were neither significantly different between transgenic and non-transgenic varieties nor among the maize varieties overall. Slugs fed with dandelion showed a significantly longer lifetime after field collection, gained significantly more weight and laid eggs. The results did not show a Bt-effect but indicated the general poor quality of maize as food resource for slugs.     

Does human proximity affect antibody prevalence in marine-foraging river otters (Lontra canadensis)?

The investigation of diseases of free-ranging river otters (Lontra canadensis) is a primary conservation priority for this species; however, very little is known about diseases of river otters that forage in marine environments. To identify and better understand pathogens that could be important to marine-foraging river otters, other wildlife species, domestic animals, and humans and to determine if proximity to human population could be a factor in disease exposure, serum samples from 55 free-ranging marine-foraging river otters were tested for antibodies to selected pathogens. Thirty-five animals were captured in Prince William Sound, Alaska (USA), an area of low human density, and 20 were captured in the San Juan Islands, Washington State (USA), an area characterized by higher human density. Of 40 river otters tested by indirect immunofluorescent antibody test, 17.5% were seropositive (titer > or =320) for Toxoplasma gondii. All positive animals came from Washington. Of 35 river otters tested for antibodies to Leptospira interrogans using the microscopic agglutination test, 10 of 20 (50%) from Washington were seropositive (titer > or =200). None of the 15 tested animals from Alaska were positive. Antibodies to Neospora caninum (n=40), Sarcocystis neurona (n=40), Brucella abortus (n=55), avian influenza (n=40), canine distemper virus (n=55), phocine distemper virus (n=55), dolphin morbillivirus (n=55), porpoise morbillivirus (n=55), and Aleutian disease parvovirus (n=46) were not detected. Identifying exposure to T. gondii and L. interrogans in otters from Washington State but not in otters from Alaska suggests that living proximal to higher human density and its associated agricultural activities, domestic animals, and rodent populations could enhance river otter exposure to these pathogens.     

Does maternal exposure to an environmental stressor affect offspring response to predators?

There is growing recognition of the ways in which maternal effects can influence offspring size, physiological performance, and survival. Additionally, environmental contaminants increasingly act as stressors in maternal environments, possibly leading to maternal effects on subsequent offspring. Thus, it is important to determine whether contaminants and other stressors can contribute to maternal effects, particularly under varied ecological conditions that encompass the range under which offspring develop. We used aquatic mesocosms to determine whether maternal effects of mercury (Hg) exposure shape offspring phenotype in the American toad (Bufo americanus) in the presence or absence of larval predators (dragonfly naiads). We found significant maternal effects of Hg exposure and significant effects of predators on several offspring traits, but there was little evidence that maternal effects altered offspring interactions with predators. Offspring from Hg-exposed mothers were 18% smaller than those of reference mothers. Offspring reared with predators were 23% smaller at metamorphosis than those reared without predators. There was also evidence of reduced larval survival when larvae were reared with predators, but this was independent of maternal effects. Additionally, 5 times more larvae had spinal malformations when reared without predators, suggesting selective predation of malformed larvae by predators. Lastly, we found a significant negative correlation between offspring survival and algal density in mesocosms, indicating a role for top-down effects of predators on periphyton communities. Our results demonstrate that maternal exposure to an environmental stressor can induce phenotypic responses in offspring in a direction similar to that produced by direct exposure of offspring to predators.     

Shrinking body sizes in response to warming: explanations for the temperature–size rule with special emphasis on the role of oxygen

Body size is central to ecology at levels ranging from organismal fecundity to the functioning of communities and ecosystems. Understanding temperature-induced variations in body size is therefore of fundamental and applied interest, yet thermal responses of body size remain poorly understood. Temperature–size (T–S) responses tend to be negative (e.g. smaller body size at maturity when reared under warmer conditions), which has been termed the temperature–size rule (TSR). Explanations emphasize either physiological mechanisms (e.g. limitation of oxygen or other resources and temperature-dependent resource allocation) or the adaptive value of either a large body size (e.g. to increase fecundity) or a short development time (e.g. in response to increased mortality in warm conditions). Oxygen limitation could act as a proximate factor, but we suggest it more likely constitutes a selective pressure to reduce body size in the warm: risks of oxygen limitation will be reduced as a consequence of evolution eliminating genotypes more prone to oxygen limitation. Thus, T–S responses can be explained by the ‘Ghost of Oxygen-limitation Past’, whereby the resulting (evolved) T–S responses safeguard sufficient oxygen provisioning under warmer conditions, reflecting the balance between oxygen supply and demands experienced by ancestors. T–S responses vary considerably across species, but some of this variation is predictable. Body-size reductions with warming are stronger in aquatic taxa than in terrestrial taxa. We discuss whether larger aquatic taxa may especially face greater risks of oxygen limitation as they grow, which may be manifested at the cellular level, the level of the gills and the whole-organism level. In contrast to aquatic species, terrestrial ectotherms may be less prone to oxygen limitation and prioritize early maturity over large size, likely because overwintering is more challenging, with concomitant stronger end-of season time constraints. Mechanisms related to time constraints and oxygen limitation are not mutually exclusive explanations for the TSR. Rather, these and other mechanisms may operate in tandem. But their relative importance may vary depending on the ecology and physiology of the species in question, explaining not only the general tendency of negative T–S responses but also variation in T–S responses among animals differing in mode of respiration (e.g. water breathers versus air breathers), genome size, voltinism and thermally associated behaviour (e.g. heliotherms).