Bioenergetics of growth of a cyprinid, Phoxinus phoxinus: the effect of ration, temperature and body size on food consumption, faecal production and nitrogenous excretion

Food consumption, faecal production and nitrogen excretion by minnows, Phoxinus phoxinus , weighing 1–5.5 g were studied at five rations ranging from starvation to ad libitum and four temperatures ranging from 5 to 15°C.
The maximum rate of food consumption (C_max) was related to body weight ( W ) and temperature ( T ) by the relationship: C _max= aW^b1T^b2 . There were significant daily variations in C_max, which tended to decline over time. Absorption efficiency increased with increasing ration size and decreasing temperature. Body weight had no significant effect on the faecal production. The equation F = a C^b1e^b2 T described the relationship between faecal production ( F ), food consumption ( C ) and temperature. Ammonia-N predominated over urea-N in the excreta of most experimental fish. The proportion of urea-N in the total nitrogen excreted was generally higher at lower rations than at higher rations. Rates of nitrogen excretion increased with increased ration size and were, to a lesser extent, influenced by temperature. Body weight had no significant effect on the nitrogen excretion by feeding minnows. The equation N = a+b_lT+b₂C described the effects of food consumption and temperature on nitrogen excretion ( N ) other than urea-N excretion. The relationship between urea-N excretion ( N_u ), food consumption and temperature was described by the equation N_u= ae^b1T ((C+1) ^b 2.
On the average, 11 % of food energy was lost in faecal production and nitrogen excretion by minnows feeding on whiteworms, Enchytraeus spp.     

The effect of body size on the standard metabolic rate of the lesser spotted dogfish

Standard metabolic rates were measured as the rate of oxygen consumption in 33 Scyliorhinus canicula , ranging in weight from 3–929 g. The amount of oxygen consumed per hour (Vo₂) changed predictably with body size according to the relationship Vo₂=0–104 ^W0.855, where W represents fish weight in g. On a weight specific basis, the level of standard metabolism in juvenile dogfish (5 g) was nearly double that measured in adults (500 g).     

Gastric emptying and the return of appetite in juvenile turbot, Scophthalmus maximus L., fed on artificial diets

Gastric emptying time in Scophthalmus maximus , when fed friable artificial pellets based on fishmeal, is composed of two phases:
(a) a delay time (t_d) during which the meal forms a bolus and which shortens with temperature, and
(b) an emptying phase (duration t_end ) which varies with meal size ( S ), body weight ( W ) and temperature (71 according to:
(where t _end is in h, S is in g, W is in g and T is °C). During the emptying phase, stomach contents decrease curvilinearly according to:
(where S_t , & S_o is in g and t is in h) in which the instantaneous digestion rate, K , varies with fish weight and temperature as:
Food pellets were prepared which remained separate and did not form a bolus in the stomach; K increased if a given meal size was subdivided to increase surface area. If meal size was increased by ingestion of identical pellets, K decreased. After a satiation meal, appetite in young turbot returns in direct relation to the degree of stomach emptiness. When food is regularly available, young turbot feed steadily at a rate which maintains their stomachs at c. 85% maximum fullness. When trained to use demand feeders, the fish interact as a group to feed rhythmically, but feeding rate falls 33% to only two-thirds of the previous rate since stomach fullness, and hence digestion rate (g h⁻¹), is maintained at a lower level. Reduction in dietary energy density below 1 kCal g⁻¹ increases gastric emptying rate and the turbot demonstrate partial compensation by increasing food intake. On energy-rich diets, protein nitrogen and energy assimilation efficiencies remain high (97 5% and 91% respectively) irrespective of feeding rate and frequency.     

Effects of solar radiation on the endemic Mediterranean red alga Rissoella verruculosa: photosynthetic performance, pigment content and the activities of enzymes related to nutrient uptake

The effects of full-spectrum solar radiation and of solar radiation deprived of total u.v. radiation (λ<395 nm) on the endemic Mediterranean red alga Rissoella verruculosa (Bertoloni) J. Agardh were studied in situ in early summer, from sunrise to sunset. Photosynthetic performance, pigment content and the activities of enzymes related to nutrient uptake, were monitored under both radiation conditions throughout a daylight period.
The doses of solar radiation, measured on the day during which the experiments were carried out (24 June 1997), were 9228·25, 1109·70 and 13·03 kJ m⁻² for PAR (λ=400–700 nm), u.v.-A (λ=315–400 nm) and u.v.-B (λ=280–315 nm), respectively. Under these conditions, a clear daily variation in photosynthetic performance was found. However, no significant differences were detected between the two radiation conditions. At noon, strong sunlight impaired O₂ evolution by 75%, but complete recovery occurred during the afternoon, reaching similar values to those measured in the early morning. By contrast, photoinhibition of optimal quantum yield ( F _v/ F _m), and the relative electron transport rate was followed by only a slight recovery during the afternoon. The rate of photosynthesis in air (simulating emersion conditions), estimated by CO₂ exchange, showed a negative balance at noon, which was accentuated in plants exposed to the full-solar spectrum.
Significant changes in the activities of nitrate reductase and carbonic anhydrase were found throughout the day under both radiation conditions. In thalli receiving solar radiation deprived of u.v., total CA activity decreased throughout the day. However, in thalli exposed to full-spectrum solar radiation, the activity of the enzyme tended to increase in the afternoon, correlating with an increase in NR activity.     

The influence of body size and temperature on oxygen consumption of the European eel, Anguilla anguilla

The effect of temperature and body size on oxygen uptake of European eels, Anguilla anguilla , was studied. The mass specific oxygen uptake of large eels was lower at all temperatures than that of small eels. The effect of temperature on metabolism was greater on small eels than on large eels. The relationship between oxygen consumption and body size is described by the equation M = a W^b , where M is metabolism (O₂ h^-1 ), W is body weight (g), b is the slope of the function which describes the relationship between body weight change and metabolism, and a is the temperature-dependent constant of the equation. In this study it was found that increased temperature caused an increase in a and a decrease in b .     

温度和个体大小对单齿螺耗氧率和排氨率的影响

采用静水法测定了不同温度、不同个体大小的单齿螺耗氧率和排氨率。结果表明:在16-33℃的实验温度范围内单齿螺的耗氧率(R_O)和排氨率(R_N)与软体部干重(W)都呈负相关,它们之间关系可以分别用幂函数R_O=aW^-b和R_N=a₁W^-b1表示。16～29℃温度范围内单齿螺的耗氧率和排氨率均随温度的升高而增加,29℃时耗氧率和排氨率达到最大值,当温度继续升高超过29℃后,耗氧率和排氨率则随温度的升高而下降,耗氧率、排氨率与温度之间呈显著的指数函数关系R_O=ce^dT和R_N=c₁e^d1T;不同个体大小单齿螺的O:N比在16～20℃时较大,Q₁₀取值范围0.56-3.74,平均值为1.64。方差分析表明,温度、软体部干重对单齿螺的耗氧率和排氨率均有极显著的影响(P<0.01)。     

Temperature-associated upper limits to body size in terrestrial poikilotherms

We show that the largest tropical species of terrestrial poikilotherms from 25 taxa exceed, in linear body size, the largest representatives of the same taxa from the temperate (e.g. Great Britain) and polar (e.g. Wrangel Island) zones by 3.2 and 5.7 times, respectively. Here we develop a theoretical approach which quantitatively explains the observed body size patterns and relates them to ambient temperature under the assumption that there exists a temperature-independent critical minimum value of mass-specific metabolic rate b_min, a fall below which is incompatible with successful biological performance. This value sets an upper limit to linear body size within a taxon. Mass-specific metabolic rate decreases with increasing body size but, in poikilotherms, grows exponentially with ambient temperature. Such compensation of the size-related drop in mass-specific metabolic rate b by higher ambient temperature extends the permitted range of body sizes for which b≥b_min. As a result, the maximum linear body size grows approximately twofold per each ten degrees of increase in ambient temperature. We also discuss why this prediction does not apply to interspecific comparisons of aquatic poikilotherms, for which an opposite trend is to be expected. We quantify in theory the maximum body size patterns recently reported for benthic gammaridean amphipods.     

Effect of body weight and temperature on the maximum daily food consumption of Gasterosteus aculeatus L. and Phoxinus phoxinus (L.): selecting an appropriate model

The relationships between the maximum, daily food consumption, body weight and water temperature for the stickleback, Gasterosteus aculeatus L. , and the minnow, Phoxinus phoxinus (L.), were studied. The two species occupy the same lakes in mid-Wales, but differ in that G. aculeatus has a true stomach whereas P. phoxinus lacks a true stomach.
For both species, the relationship between food consumption (F) and body weight ( W ) could be described by the model: log_eF=a + b log_e W . The effect of temperature (T) could be incorporated in the form: log_ef= a + b, log_e W+b₂log_e T. These models were selected because they accounted for a high proportion of the variance in the dependent variable, and because an analysis of the residuals obtained after fitting a model showed no trends which would have signalled the inadequacy of the model.     

Growth studies with fish—overcoming the problems of size variation

The relationship between growth rate and fish size is described by the equation log_e G _w= a —0·4 log_e W, where G_w is the specific growth rate and W is fish weight. Since the intercept (a) represents the log_e G_w of a fish unit size, the relationship presents a method allowing comparison of data from experiments involving fish of different sizes. The application of the method is demonstrated by examining the effects of environmental temperature on growth rates of cod, Gadus morhua , and it is suggested that the optimum temperature for growth of cod is 13–15° C.     

Constraints of body size and swimming velocity on the ability of juvenile rainbow trout to endure periods without food

The hypothesis that body size and swimming velocity affect proximate body composition, wet mass and size‐selective mortality of fasted fish was evaluated using small (107 mm mean total length, L _T) and medium (168 mm mean L _T) juvenile rainbow trout Oncorhynchus mykiss that were sedentary or swimming ( c . 1 or 2 body length s⁻¹) and fasted for 147 days. The initial amount of energy reserves in the bodies of fish varied with L _T. Initially having less lipid mass and relatively higher mass‐specific metabolic rates caused small rainbow trout that were sedentary to die of starvation sooner and more frequently than medium‐length fish that were sedentary. Swimming at 2 body length s⁻¹ slightly increased the rate of lipid catabolism relative to 1 body length s⁻¹, but did not increase the occurrence of mortality among medium fish. Death from starvation occurred when fish had <3·2% lipid remaining in their bodies. Juvenile rainbow trout endured long periods without food, but their ability to resist death from starvation was limited by their length and initial lipid reserves.     

DEPTH DISTRIBUTIONS OF DNA DAMAGE IN ANTARCTIC MARINE PHYTO- AND BACTERIOPLANKTON EXPOSED TO SUMMERTIME UV RADIATION

During a survey from January to March 1998, the occurrence of UV-B radiation (UVBR)- induced DNA damage in Antarctic marine phytoplankton and bacterioplankton was investigated. Sampling was done in Ryder Bay, off the British base Rothera Station, 67°S, 68°W (British Antarctic Survey). Samples were taken regularly during the survey period at fixed depths, after which DNA damage was measured in various plankton size fractions (>10, 2–10, and 0.2–2 μm). Incident solar radiation was measured using spectroradiometry, whereas attenuation of biologically effective UVBR was studied using a DNA dosimeter. A diatom bloom was found in the bay during the research period, judging from microscopic observations and HPLC analyses of taxon-specific pigments. The high phytoplankton biomass likely caused strong attenuation of DNA effective UVBR (K_bd-eff). K_bd-eff values ranged from 0.83·m ^{− 1} at the peak of the bloom to 0.47·m ^{− 1} at the end of the season. UVBR-mediated DNA damage, as measured by cyclobutane pyrimidine dimer (CPD) abundance, was detected in all plankton size fractions. Highest levels were found in the smallest size fraction, mainly consisting of heterotrophic bacteria. Clear CPD depth profiles were found during mid-summer (January, beginning of February) with surface levels exceeding 100 CPDs per million nucleotides in the bacterioplankton fraction. At that time, melting of the continuously present shelf ice caused strong salinity gradients in the upper meters, thereby stimulating water column stabilization. At the end of February and beginning of March, this phenomenon was less pronounced or absent. At that time, DNA damage was homogeneously distributed over the first 10 m, ranging between 20 and 30 CPDs per million nucleotides for the smallest size fraction.     

The effects of temperature, pH and water hardness on winter starvation of young-of-the-year smallmouth bass, Micropterus dolomieui Lacepede

Year-class strength in northern populations of smallmouth bass is strongly influenced by winter starvation of young-of-the-year. We examined starvation among young bass under both winter and summer light and temperature conditions. During starvation, body condition declines to a specific level and then the fish dies. Body condition at death is a well defined function of body size that remains relatively constant over a wide range of environmental conditions. Starvation rate varies systematically with body size, temperature, pH and water hardness. Available stored energy increases more rapidly with body size than starvation rate. Therefore, lifetime under starvation conditions tends to increase with increasing body size. The Q₁₀ for starvation rate over the temperature range 2.5-8° C is 2.2. Starvation rate increases as pH declines from 7.0-4.9: the rate at pH 4.9 is ∼ 1.25 times the rate at pH 7 Starvation rate decreases as Ca concentration increases from 1 mgl⁻¹ to 80mgl⁻¹: the rate at 80 mg Ca 1⁻¹ is ∼0.80 times the rate at 1 mgl⁻¹.     

Partitioning of metabolizable energy intake in sucking altricial and precocial rodent pups

We partitioned the metabolizable energy intake (MEI) into energy for maintenance (ME_m) and for growth (ME_g) in sucking precocial and altricial rodent pups. Each of the two components includes energy loss due to the heat increment of feeding. ME_m of precocial pups expressed as average daily energy costs or as a proportion of MEI was greater than in altricial pups of similar size and, therefore, less energy was available for growth. Consequently, the overall energy cost (via total MEI) per unit postnatal growth of precocial pups was greater than for altricial pups of similar size. We used the proportion of calculated ME_m to that predicted by body mass as an index of precociality in rodent pups. The proportion of ME_g to MEI in precocial pups was lower than in altricial pups and was inversely related to the index of precociality.     

Radiation frost susceptibility and the association between sky exposure and leaf size

Plants growing in exposed and sheltered habitats have characteristic leaf structure and physiology that are traditionally associated with the total amount of incident sunlight. However, greater sky exposure also increases the susceptibility of leaves to radiation frost. Plants with large horizontal broadleaves are particularly susceptible to both overheating during the day and freezing at night. Moreover, the combined effects of high daytime sun-exposure and nighttime frost susceptibility could be particularly stressful to plant tissues. The purpose of this study was to evaluate the influence of elevation and microsite exposure (i.e. net loss of longwave radiation) on frost susceptibility, as well as the corresponding intraspecific variation in leaf size in the subalpine daisy (Erigeron peregrinus). Measured decreases in upper hemisphere infrared radiation (sky IR) of 0.014 W m^-2 m^-1 occurred with increasing elevation, beyond decreases predicted due to changes in air temperature and water content, resulting in an average decrease of 0.029 W m^-2 m^-1. Previous equations of sky IR based on air temperature and humidity were improved by adding this elevational term (r ² improved from 0.52 to 0.71). In contrast, a mean decrease of 6.5 W m^-2 m^-1 occurred with increasing sky exposure across a subalpine meadow. Leaf size in Taraxacum officinale decreased linearly with increasing elevation and a corresponding decline in sky IR. No difference in daily solar irradiance was measured across the same elevational gradient. Also, E. peregrinus had smaller leaves at high elevation microsites with greater sky exposure and decreased sky IR, while there was a much weaker association between leaf size and the amount of total daily solar irradiance. Differences in plant leaf structure and physiology traditionally associated with daytime sun-exposure may also be influenced by nighttime sky exposure and the susceptibility to radiation frosts.     

Effects of solar radiation and solar radiation deprived of UV-B and total UV on photosynthetic oxygen production and pulse amplitude modulated fluorescence in the brown alga Padina pavonia

Abstract: The effects of solar radiation on photosynthetic oxygen production and pulse amplitude modulated (PAM) fluorescence were measured in the marine brown macroalga Padina pavonia harvested from different depths from the Greek coast near Korinth. In fluence rate-response curves the light compensation point for photosynthetic oxygen production increased and the saturation level decreased with increasing exposure time to solar radiation. Cutting off the UV-B wavelength range (280–315 nm) from solar radiation reduced the inhibition of photosynthesis, and the organisms were less affected when all of the UV radiation was filtered out. Algae collected from 7 m depth were much more prone to photoinhibition than those harvested from rock pools exposed to unfiltered solar radiation. During continuous exposure to solar radiation, rock pool algae showed photoinhibition after longer periods of time than specimens from 7 m or from dark adapted habitats. When subjected to unfiltered solar radiation the ratio of the variable fluorescence to the maximal fluorescence     (F_v = F_m− F_o) rapidly declined with increasing exposure time. However, again algae from 7 m depth were more prone to photoinhibition than rock pool algae. The differences between the two ecological strains were less obvious when UV-B or total UV was removed from solar radiation. Only in the latter case a complete recovery was observed after 2 h while, when exposed to unifiltered sunlight, only the rock pool algae recovered completely within that time.     

Energetics and foraging behaviour of the European seed harvesting ant Messor capitatus: I. Respiratory metabolism and energy consumption of unloaded and loaded workers during locomotion

Abstract The respiratory metabolism of workers of Messor capitatus (Latreille) was measured using standard micro-Warburg techniques on single individuals. The experiments were carried out at 10, 20, 25, 30 and 40^oC, and the respiratory quotient (RQ), measured for the same individuals at 30^oC, was found to be 0.77. The specific respiratory rate (y , in μl O₂/mg dry weight/h) could be described by the following equation: Iny = -2.24 + 0.098r -0.258 In W; where T is temperature and W is the dry weight in mg. The Q₁₀ for M. capitatus in the temperature interval 20–30^oC was 3.4, a higher value than for other ants.
The energy costs of movement and carrying were determined by using the RQ to convert the continuous measurement of CO₂ produced at 30^oC by Enfiuran anaesthetized workers ('resting metabolism'), by running workers and by workers loaded with a 20 mg weight to units of energy. The resting metabolism was 10.0±1.0 mJ/mg fresh weight/h. The cost of running ( Y in joule per km) could be described by: Y = 3.865 + 0.363 Wf , where Wf is fresh weight in mg. The cost of transport for all experiments could be expressed as 0.64 × the cost of running.     

Foraging energetics of Grey-headed Albatrosses Diotnedea chrysostoma at Bird Island, South Georgia

At-sea metabolism (CO₂ production) and water turnover of six breeding Grey-headed Albatrosses Diomedea chrysostoma were measured, using the doubly labelled water method, at Bird Island, South Georgia, Mean food consumption (estimated from a water influx rate of 1.01 1 d^-1 and data on dietary composition) was 1200gd^-1 or 50.4 W. At-sea metabolism (derived from a rate of CO₂ production of 3.98 1 h^-1) was 27.7 W, 2.5 times the estimated basal metabolic rate (BMR). On average the birds ingested nearly twice as much food energy as they expended to obtain it. The metabolic rate during flight (estimated from at-sea metabolism and activity budget data) was 36.3 W (range 34.7–39.0 W) or 3.2 (range 3.0–3.4) times the predicted BMR. This is the lowest cost of flight yet measured, but consistent with the highly developed adaptations for economic flight shown by albatrosses. These results are briefly compared with data for other polar vertebrates (penguins, fur seals) exploiting similar prey.     

Effects of supplemental UV-B radiation on growth and leaf photosynthetic reactions of soybean (Glycine max)

Experiments were conducted under greenhouse conditions to investigate the effects of enhanced UV-B radiation (280 to 320 nm) on height, fresh and dry weights, leaf chlorophyll and carotenoids, CO₂ uptake rates, and Hill activity in soybean ( Glycine max L. cv. Bragg). Plants were exposed for 6 h continuously from midmorning to midafternoon each day to UV-B radiation which was provided by Westinghouse FS-40 sun lamps filtered with 0.127-mm cellulose acetate film (UV-B enhanced) or 0.127-mm Mylar S film (UV-B Mylar control). Three different UV-B enhanced radiation levels were tested: 1.09 (treatment T₁), 1.36 (treatment T₂), and 1.83 (treatment T₃) UV-B sun equivalent units (UV-B_sec) where 1 UV-B_sec= 15.98 mW·m⁻² of solar UV-B obtained by applying EXP -[(α-265)/21]², a weighting function that simulates the DNA absorption spectrum, to the UV-B lamp systems. These UV-B levels correspond to a calculated decrease in stratospheric ozone content of 6%, 21%, and 36% for treatment T₁, T₂, and T₃, respectively.
Daily exposure of soybean plants to UV-B radiation significantly decreased height, fresh and dry weights, leaf chlorophyll and carotenoid contents, and CO₂ uptake rates. Leaf pigment extracted in 80% acetone from UV-B-treated soybean plants showed considerable increase in absorption in the wavelength region of 330 to 400 nm with increased UV-B radiation levels. Chloroplast preparations from leaves of T₂ and T₃ plants showed significant reductions in Hill reaction measurements.     

The adaptive significance of alpine melanism in the butterfly Parnassius phoebus F. (Lepidoptera: Papilionidae)

Summary The adaptive significance of alpine melanism, the tendancy for insects to become darker with increased elevation and latitude, was investigated using the butterfly Parnassius phoebus. The effects on temperature dependent activity of five components of overall wing melanism, as well as size, were examined. The components of wing melanism examined were the transparency of the basal hindwing and distal fore-wing areas, the width of the black patch in the basal hind-wing area and the proportion of black to white scales in that area, and the proportion of the distal fore-wing covered by predominantly black scaling.The body temperature of dead specimens was correlated with air temperature, solar radiation, the width of the black patch at the base of the wings, and the proportion of black to white scales at the base of the wings. The minimum air temperatures and solar radiation levels required for initiation of flight did not vary with wing melanism of P. phoebus, in contrast to the results found for Colias butterflies by Roland (1982). However, under environmental conditions suitable for flight initiation, males with a higher proportion of black to white scales in the basal area of the hind-wing, and wider basal black patches, spent a greater proportion of time in flight at low air temperatures and low insolation. Increased basal wing melanism was also associated with increased movement of males within a population. In contrast, melanism in the distal area of the wings has no effect on activities which are dependant on body temperature. The amount of time spent feeding did not vary with differences in wing melanism. I suggest that in dorsal basking, slow-flying butterflies (Parnassius) basal wing color affects body temperature primarily during flight (rather than while basking), such that butterflies with darker wing bases cool down less rapidly because they absorb more solar radiation during flight.     

UV effects on photosynthesis and phycobiliprotein composition in the flagellate Cyanophora paradoxa

Abstract The effects of solar and artificial ultraviolet radiation on photosynthetic oxygen production and phycobiliprotein composition were investigated in the freshwater flagellate, Cyanophora paradoxa . The phycobiliproteins of the cell acting as photosynthetic accessory pigments were found to be readily affected by even short exposure to ultraviolet radiation, while the membrane-bound chlorophyll protein complexes were hardly impaired as demonstrated by SDS polyacrylamide gel electrophoresis, isoelectric focussing and fast protein liquid chromatography (FPLC). The phycobilisomes are dissembled from the outside inwards and go from higher molecular weight components to hexamers (αβ)₆, trimers (αβ)₃ and finally monomers (αβ). Fluorescence spectra indicated that the energy transfer from accessory pigments to the photosystems was impaired by ultraviolet radiation. Photosynthetic oxygen production was affected on a much faster timescale than changes in the absorption spectra or at the protein level.