The diet and growth of O-group flounder,Platichthys flesus (L.), in the River Dee,North Wales

Many O-group flounder, Platichthys flesus, live in the lower reaches of rivers in North West Europe; while there is extensive information on the niche that they occupy in estuarine and marine environments, little is known of their life in freshwater. The diet of O-group flounder in the Lower Welsh River Dee was studied by stomach contents analysis of diel and seasonal samples. The dominant prey were chironomid larvae and pupae, tubificid oligochaetes and cyclopoid copepods. There was little quantitative variation in diet temporally, although a weak crepuscular pattern of stomach fullness was shown. There was wide variation in length and weight in all months, but the mean values at age I were 60 mm and 2.9 g respectively.     

The combined effect of feeding time and ration on growth performance and nitrogen metabolism of greenback flounder

Greenback flounder Rhombosolea tapirina ( c. 2 g) fed to satiation had significantly ( P <0·01) higher feed consumption in the evening than in the morning whereas there was no difference between feeding times for flounder fed restricted rations (1 or 2% body weight per day) because they consumed all of the ration. Differences in growth performance were due to feeding time and ration. Carcass moisture, lipid and energy content were significantly ( P <0·001) different between rations; length gain was significantly affected by feeding time ( P <0·05) and ration ( P <0·001); weight gain showed a significant ( P <0·001) interaction between feeding time and ration. The relationship between feed consumption and specific growth rate showed that the exponential gradient was significantly higher ( P <0·01) for the evening fed fish and indicated feed efficiency for evening fed fish increased as feed consumption increased. Urea excretion increased from 12–20 to 58–63% of total nitrogen excretion at the 1 and 3% rations, respectively. Ammonia and urea excretion were significantly affected by ration ( P <0·001) and feeding time ( P <0·05). Fish fed the 2% ration in the evening had higher growth efficiency and significantly ( P <0·01) lower rates of urea excretion than fish fed 2 or 3% ration in the morning. It is suggested that the higher energetic costs associated with differences in ammonia and urea excretion contributed to differences in growth efficiency.     

Dynamic Profiling of Protein Mole Synthesis Rates during C2C12 Myoblast Differentiation

Mole (MSR) and fractional (FSR) synthesis rates of proteins during C2C12 myoblast differentiation are investigated. Myoblast cultures supplemented with D₂O during 0–24 h or 72–96 h of differentiation are analyzed by LC‐MS/MS to calculate protein FSR and MSR after samples are spiked with yeast alcohol dehydrogenase (ADH1). Profiling of 153 proteins detected 70 significant (p ≤ 0.05, FDR ≤ 1%) differences in abundance between cell states. Early differentiation is enriched by clusters of ribosomal and heat shock proteins, whereas later differentiation is associated with actin filament binding. The median (first–third quartile) FSR (%/h) during early differentiation 4.1 (2.7–5.3) is approximately twofold greater than later differentiation 1.7 (1.0–2.2), equating to MSR of 0.64 (0.38–1.2) and 0.28 (0.1–0.5) fmol h^?1 µg^?1 total protein, respectively. MSR corresponds more closely with abundance data and highlights proteins associated with glycolytic processes and intermediate filament protein binding that are not evident among FSR data. Similarly, MSR during early differentiation accounts for 78% of the variation in protein abundance during later differentiation, whereas FSR accounts for 4%. Conclusively, the interpretation of protein synthesis data differs when reported in mole or fractional terms, which has consequences when studying the allocation of cellular resources.     

Effects of long-term supplementation of chestnut and valonea extracts on methane release,digestibility and nitrogen excretion in sheep

The long-term effects of adding chestnut (CHE; Castanea sativa) and valonea (VAL; Quercus valonea) tannin-rich extracts to sheep feed were investigated. In Experiment 1, sheep (65 kg BW) were fed 842 g/day of a ryegrass-based hay. The control-treated animals (CON) received 464 g/day of concentrate, and tannin-treated animals received the same amount of concentrate additionally containing 20 g of the respective tannin-rich extract. Hay and concentrates were offered together in one meal. After the onset of treatment, methane release was measured in respiration chambers for 23.5-h intervals (nine times) in a 190-days period. Faeces and urine were collected three times (including once before the onset of the tannin treatment) to assess digestibility and urinary excretion of purine derivatives. Based on the results obtained from Experiment 1, a second experiment (Experiment 2) was initiated, in which the daily tannin dosage was almost doubled (from 0.9 (Experiment 1) to 1.7 g/kg BW^0.75). With the exception of the dosage and duration of the treatment (85 days), Experiment 2 followed the same design as Experiment 1, with the same measurements. In an attempt to compare in vitro and in vivo effects of tannin supplementation, the same substrates and tannin treatments were examined in the Hohenheim gas test. In vitro methane production was not significantly different between treatments. None of the tannin-rich extract doses induced a reduction in methane in the sheep experiments. On the 1st day of tannin feeding in both experiments, tannin inclusion tended to decrease methane release, but this trend disappeared by day 14 in both experiments. In balance period 3 of Experiment 1, lower dry matter and organic matter digestibility was noted for tannin treatments. The digestibility of CP, but not NDF or ADF, was reduced in both experiments. A significant shift in N excretion from urine to faeces was observed for both tannin-rich extracts in both experiments, particularly in Experiment 2. In balance period 2 of Experiment 2, an increased intake of metabolisable energy for VAL was observed. The urinary excretion of purine derivatives was not significantly different between treatments, indicating that microbial protein synthesis was equal for all treatments. Thus, we concluded that both tannin-rich extracts temporary affect processes in the rumen but did not alter methane release over a longer period.     

Feeding ecology of juvenile turbot Scophthalmus maximus and flounder Pleuronectes flesus at Gotland, Central Baltic Sea

Food and feeding of juvenile turbot Scophthalmus maximus and flounder Pleuronectes flesus were studied in five nursery areas at Gotland, Central Baltic Sea, ICES SD 27 and SD 28. Ontogeny involved partitioning of available food resources. The food choice of turbot <30 mm standard length (L_S) included both planktonic‐hyperbenthic prey (calanoid copepods and mysids) and epibenthic–endobenthic prey (chironomids and amphipods), whereas turbot ≥30 mm L_S fed mainly on hyperbenthic species (mysids and fishes). Conversely, for flounder, epibenthic–endobenthic prey were the most abundant prey items throughout development (harpactocoid copepods, oligochaetes and chironomids for fish <40 mm L_S and oligochaetes, chironomids and amphipods for flounder ≥40 mm L_S). Thus, the highest degree of dietary overlap occurred between turbot <30 mm and flounder ≥40 mm. Food composition for both turbot and flounder varied, however, according to exposure and predominant wind direction in the nursery area. For example, expressed as the ratio between the biomass of mysids and fishes consumed, the relative importance of mysids v. fishes as food source for turbot, varied from <1 in the most sheltered area to 16 and 27 in the more open areas. Considerable differences in feeding incidence were recorded; mean ±s .d . 58 ± 20% for turbot <30 mm L_S and 83 ± 8% for turbot ≥30 mm L_S, as opposed to ≥85–90% for flounder irrespective of size. The lower feeding success of turbot <30 mm L_S was related to mysid abundance, shown to vary spatially and temporally, and to density of flounder, indicating that food availability, and potentially interspecific competition, influence feeding of early juvenile turbot with implications for survival following settlement. Regarding variability in abundance, hyperbenthic prey, as mysids, are considered more variable than epi‐ and endobenthic organisms. Hence, in addition to the ‘nursery size hypothesis’, i.e. the positive relationship between abundance of recruits and extension of nursery areas, variability in food availability may explain the average lower recruitment of turbot as compared to other flatfishes, e.g. flounder.     

Protein synthesis in distal axons is not required for axon growth in the embryonic spinal cord

It is now well established that new proteins are synthesized in the distal segments of elongating axons, where they may play an essential role in some guidance decisions. It remains unclear, however, whether distal protein synthesis also plays an essential role in axon growth per se. Previous in vitro experiments have shown that blocking protein synthesis in distal axons has no effect on the rate of axonal advance. However, because these experiments were performed in vitro and over a relatively short time period, the role of distal protein synthesis over longer periods and in a native tissue environment remained untested. Here, we tested whether protein synthesis in distal axons plays an essential role in the elongation of descending axons in the embryonic spinal cord. We developed an in situ model of the brainstem-spinal projection of the embryonic chick, and developed a split-chamber method in which inhibitors of proteins synthesis could be applied independently to cell bodies in the brainstem or to distal axons in the spinal cord. When protein synthesis was blocked in distal axons, axon growth remained robust for 2 days, which is the length of the experiment. However, when protein synthesis was blocked only in the brainstem, axonal elongation in the spinal cord ceased within 6 h. These data showed that protein synthesis in the distal axon is not essential to continue the advance of axons. Rather, essential proteins are synthesized more proximally and then transported rapidly to the distal axon.     

Development, validation and field application of an RNA-based growth index in juvenile plaice Pleuronectes platessa

A general mechanism relating RNA concentration and growth rate is derived from four physiological assumptions and developed into a growth index for juvenile plaice Pleuronectes platessa. The index describing instantaneous growth rates (G, day^?1) in the laboratory with the lowest Akaike information criterion with small‐sample bias adjustment was a function of RNA concentration (R, ), temperature (T, ° K), body mass (M, g) and DNA concentration (D, ): G = β₀ + β_RR + β_TT + β_T2T² + β_MM + β_DD + β_RTRT. RNA concentration began to respond to changes in feeding conditions within 8 days, suggesting that the index reflects growth rate in the short‐term. Furthermore, the index distinguished between rapid growth and negative growth of juvenile P. platessa measured directly in laboratory and field enclosures, respectively. An application of the RNA‐based growth index at two beaches on the west coast of Scotland suggested that the growth of juvenile P. platessa varies considerably in space and time and is submaximum in late summer.     

Effect of various kinds of dietary protein and supplementation with limiting amino acids on growth,haemolymph components and uric acid excretion in the silkworm, Bombyx mori

Effects of various kinds of dietary protein on growth of the silkworm, Bombyx mori, were determined using semi-synthetic diets. Also, the ingestion, digestion and utilization of dry matter and of nitrogen were measured. Nutritive effects of dietary proteins and supplementation of limiting amino acids on haemolymph protein and amino acids pattern were also investigated. Larval growth was largely dependent on the dietary proteins. When the larvae were reared on a diet containing weakly nutritive proteins such as gluten and zein, haemolymph protein was decreased and uric acid excretion was markedly accelerated. The free amino acid composition of the haemolymph manifested characteristic patterns according to the kinds of dietary protein.The supplementation of gluten and zein with their limiting amino acids resulted in a rise of haemolymph protein and a drop in uric acid excretion. The amino acid patterns in the haemolymph were greatly changed according to supplementation.     

Oxygen consumption, ammonia excretion and protein use in response to thermal changes in juvenile Atlantic salmon Salmo salar

Experiments were designed to examine the effects of various temperature challenges on oxygen consumption and ammonia excretion rates and protein utilization in juvenile Atlantic salmon Salmo salar . Fish acclimated to 15° C were acutely and abruptly exposed to either 20 or 25° C for a period of 3 h. To simulate a more environmentally relevant temperature challenge, a third group of fish was exposed to a gradual increase in temperature from 15 to 20° C over a period of 3 h ( c. 1·7° C h⁻¹). Oxygen consumption and ammonia excretion rates were monitored before, during and after the temperature shift. From the ammonia excretion and oxygen consumption rates, protein utilization rates were calculated. Acute temperature changes (15–20° C or 15–25° C) caused large and immediate increases in the oxygen consumption rates. When the temperature was gradually changed ( i.e. 1·7° C h⁻¹), however, the rates of oxygen consumption and ammonia excretion were only marginally altered. When fish were exposed to warmer temperatures ( i.e. 15–20° C or 15–25° C) protein use generally remained at pre-exposure (15° C) levels. A rapid transfer back to 15° C (20–15° C or 25–15° C) generally increased protein use in S. salar . These results indicate that both the magnitude and the rate of temperature change are important in describing the physiological response in juvenile salmonids.     

Feeding ecology and growth of age 0 year Platichthys flesus(L.) in a vegetated and a bare sand habitat in a nutrient rich fjord

A study was carried out to investigate the diet and feeding strategies of age 0 year juvenile flounder Platichthys flesus in two different micro‐tidal habitats in the nutrient enriched Mariager Fjord on the Danish east coast. Juvenile flounder and benthic macrofauna were sampled monthly from June to October 1999 in a bare sand habitat and a habitat covered by filamentous and mat forming macroalgae. The presence of the 'opportunistic' macroalgae created a shift in the dominance of surface dwelling prey such as epifaunal amphipods to more infaunal groups such as oligochaetes and polychaetes. The diet of the flounder varied considerably between the two habitats mainly reflecting prey availability relative to their abundance, prey spatial distribution, habitat structure and ontogenetic prey shifts as a function of total length. Flounder in the vegetated site fed on a diverse diet of copepods, polychaetes and oligochaetes, whereas those caught in the bare sand site fed primarily on the amphipod Corophium volutator which was numerically dominant at this site. During the growth season, two diet shifts were observed: from copepods early in the season to macrofauna organisms and, later in the season, the inclusion of more hyperbenthic prey such as Mysidea spp; Idotea spp. and the common goby Pomatoschistus microps .     

The adenohypophysis of the flounder,Pleuronectes flesus,and the minnow,Phoxinus phoxinus

Summary The pituitary gland of the flounder, Pleuronectes flesus, showed several unusual cytological features. Between the RPD and the PPD was a zone of cells that stained purple with Alcian blue—PAS—orange G. Many of these cells were apparently degenerating. In the PPD the strands and coils of presumptive STH cells showed a tremendous variation in both size and staining properties. In the PI there were two cell types, the PAS-positive one bordering the neurohypophysis. Around the periphery of the PI was a zone of chromophobic cells, and throughout the PI were numerous intracellular and extracellular acidophil spheres.No well defined ACTH cells were found in the RPD of the minnow (Phoxinus phoxinus). The Alcian blue—PAS—orange G technique distinguishes between blue TSH cells and purple GTH cells in the RPD and PPD. GTH cells from animals collected in the winter were vacuolated. The PI contained two cell types whose staining reactions and ultrastructure were extremely variable. Intra- and extra-cellular acidophil spheres were present.I should like to thank Dr. T. Kerr of the Zoology Department, Leeds University, for his help and encouragement, and Mr. J. Dingley of the Department of Zoology, Aberystwyth, for collecting the flounders.     

Evaluating model predictions of partitioning nitrogen excretion using the dairy cow model, Molly

Computer models of dairy cow digestion and metabolism are useful tools to evaluate rations and estimate nitrogen (N) excretion. Using models, different management strategies and/or feeding practices can be evaluated and their impact on N excretion explored before implementation. Critical parameters for developing nutrient management plans can be identified to help reduce the impact of animal manure. However, before a model is implemented, errors associated with predictions and limitations of the model must be known. Otherwise, proposed management and feeding changes may not result in effective measures to optimally manage N excretion. The objective of this research effort was to determine whether or not Molly, a dynamic model of dairy cow digestion and metabolism [Baldwin, R.L., 1995. Modeling Ruminant Digestion and Metabolism. Chapman & Hall, UK], could be used to predict N excretion. In Molly, predictions of N excretion are based on level of milk production (ucells) and rate of insoluble protein hydrolysis (KPiAa). Accurate estimation of N excretion patterns would indicate that understanding of N metabolism as represented in Molly is adequate. Failures indicate that more research is needed. To examine estimates of N excretion, N balance data from 18 publications in the Journals of Dairy and Animal Science were simulated using Molly. Input data required included diet composition (N intake), initial bodyweight, days in milk, dry matter intake and milk production. A total of 73 different simulations (73 different diets) with N intakes ranging from 0.19 to 0.78 kg/d and crude proteins of 106–206 g/kg were run. Model outputs of milk, milk protein, faecal N, urinary N and milk N were compared to observed data. Overall, the model simulated reality well. Mean bias are less than 11% for milk yield, milk protein, faecal N, urinary N and milk N with coefficients of determination of 0.94, 0.73, 0.70, 0.80 and 0.88, respectively. Mean absolute errors and root mean square prediction errors are also low compared with observed mean milk, milk protein, faecal N, urinary N and milk N. N excretion losses due to volatilisation were not included in model estimates of faecal N and urinary N. Predicted rates of insoluble protein hydrolysis (KPiAa) from estimating N excretion indicated that current estimates of fractions of undegraded protein for individual feedstuffs in Rumen Nitrogen Usage [National Research Council (NRC), 1985. Ruminant Nitrogen Usage. National Academy Press, Washington, DC] are not adequate.     

Effects of temperature on growth and metabolism in juvenile turbot

The effects of constant temperatures on growth, food efficiency, and physiological status were studied in four different batches of juvenile turbot. The growth responses were studied in three experiments lasting 70–85 days under 8–20° C thermal conditions. There was a positive correlation between growth and temperature from 8 to 17° C and a plateau was observed from 17 to 20° C. In fish fed to satiety, specific growth rate was positively correlated to the food intake, which was double at 20° C, compared with 8° C. Minor changes were observed in food efficiency. Body fat deposition decreased as temperature increased (25% lower at 20° C, compared with 8° C). Apparent food conversion, PER (protein efficiency ratio) and PUC (protein utilization coefficient) ranges were 0.8–0.9, 2.1–2.3 and 33–38% respectively. In 70–300 g fish, routine MO₂ increased (2.5–6.5 μmol O₂ h^?1 g bw^?1) with temperature up to 20° C, while larger turbot (500–600 g) appeared relatively thermo-independent, with a lower oxygen consumption (1.5 ìmol h^?1 g^?1). The average daily total ammonia nitrogen (TAN) and urea-N excretion per fish biomass was positively related to temperature. TAN was 30% lower at 8° C, compared with 20° C. Ingested nitrogen was mainly excreted under the final form of TAN, urea-N representing 26% of the total amount. A post-prandial peak in TAN and a delayed peak in urea-N nitrogen were observed. The hydromineral status [osmolarity, sodium, chloride and potassium blood plasma, gill (Na⁺-K⁺)-ATPase activity] of turbot was not affected by progressive changes in temperature during the acclimation period. Juvenile turbots show remarkable homeostatic capacities and so they have a relatively thermo-independent physiology within the range of temperature studied.     

Replacement perfusion of cultured eucaryotic cells: A method for the accurate measurement of the rates of growth,protein synthesis,and protein turnover

The fractional rates of protein synthesis (k_s) and degradation (k_p) were studied in the myeloma cell line SP2/0-AG14 grown at different rates (k_g). Cells in spinner flask suspension cultures were maintained at constant cellular density for prolonged periods by replacement perfusion of labeling medium at a rate equivalent to the rate of growth. Total protein synthesis was calculated from the specific-radioactivity of labeled L-leucine in the precursor (medium) and cellular protein. Fractional synthesis rates determined by approach to equilibrium labeling were the same as those determined by equilibrium-pulse labeling kinetics and pulse-chase kinetics. The rate of protein degradation was determined from the established relationship k_g = k_s – k_p. Protein synthesis rates remained constant over a threefold range in the rate of cell growth. At relatively slow growth rates (k_g = 0.017/hr) turnover represented a major fraction of total synthesis (k_p = 0.032/hr = 0.65ks). At rapid growth rates (k_g = 0.058/hr) the value of k_p was less than 0.005/hr. No major difference was observed between the k_s determined for individual cellular proteins (separated by SDS-polyacrylamide (7.5%) gel electro-phoresis) from rapid- and slow-growing cultures. Thus, with an invariable k_s, any change in growth rate is due to an inverse change in the rate of turnover. Since turnover is the balance between synthesis and degradation and since synthesis is unchanging then changes in the growth rate of SP2/0-AG14 should be due to changes in the rate of protein degradation. Experiments were therefore performed to determine the origin of the degradative machinery, ie, cytosolic or lysosomal; autolysis of prelabeled cellular protein (in vitro) was observed only at acidic pH (4.2) and WUS totally inhibited by addition of lcupcptin (10 μM) and pepstatin (2 μM), the specific inhibitors of lysosomal cathepsins B (L) and D, respectively. Since growth rate appears to be regulated by the alterations in the rate of protein degradation and degradation (in vitro) in SP2/0-AG14 appearsto be lysosomal, then one should be able to alter the rate of cellular growth by interfering with rate of lysosomal proteolysis. Indeed, when the lysosomotropic amine NH ₄Cl (10 mM) is added to cells growing with a k_g of 0.018/hr ± 0.001 (k_s = 0.050/hr ± 0.002) the growth rate increased to 0.051/hr ± 0.002 without change in the rate of protein synthesis (k_s = 0.049/hr ± 0.003). It is suggested from our data that the cellular growth rate of SP2/0-AG14 is regulated by the lysosomal apparatus; whether this regulation is itself regulated by either a specific compartmentalization of the lysosomal proteinases and/or their substrates or by endogenous protease inhibitors, should prove to be an exciting area for future investigation.     

鄂尔多斯高原3个水土保持树种的水分利用策略

为了解植物对环境的适应对策,通过测定鄂尔多斯高原东部丘陵区3个水土保持树种沙棘、油松和山杏的枝条木质部水和各潜在水源的δ¹⁸O值及叶片的δ¹³C值,应用多元线性混合模型分析各潜在水源的贡献比例,分析3个树种水分来源和水分利用效率的季节动态和种间差异。结果表明: 沙棘、油松和山杏在5月主要利用10 cm深度土壤水,分别占其总水源比例的88.5%、94.0%和91.6%。7月,沙棘主要利用10～25 cm土层土壤水和雨水,比例为44.6%和35.4%;油松主要利用雨水,比例为93.7%;山杏主要利用25～100 cm土层土壤水和雨水,比例分别为55.9%和36.8%。9月,沙棘主要利用25 cm深度和75～100 cm土层土壤水,比例为88.9%;油松主要利用10 cm和50～75 cm土层土壤水,比例为84.5%;山杏利用10～100 cm土层土壤水。5月沙棘的水分利用效率显著高于7月和9月。7月油松的水分利用效率显著高于9月。5月和7月沙棘的水分利用效率显著高于油松和山杏。3个树种在不同季节根据不同水源的可利用性,选择利用不同深度的土壤水或雨水。沙棘和油松干旱时能够提高水分利用效率适应环境变化,可能比山杏更适应当地的半干旱环境。     

Influence of salinity on the migration of postlarval and juvenile flounder Pleuronectes flesus L. in a gradient experiment

The behaviour of the flounder Pleuronectes flesus was observed in an experimental aquarium that consisted of five connected units with decreasing salinity from 20 to 15, 10, 5 and 0·5. This experimental aquarium was highly effective for studying behaviour in salinity gradients, because the gradient was relatively stable. After 4 days of observation, significantly more flounder were found in water with a salinity of 0·5, indicating a preference for fresh water. The total length of the flounders ranged from 7·5 to 21 mm. The majority of larvae had already started eye‐migration, however, the longer specimens had completed metamorphosis. The migration towards low salinities was observed to increase with ontogenetic development.