Effect of diet on oxygen uptake rate in the talitrid amphipod Platorchestia platensis

ABSTRACT

The primary ecotope for Platorchestia platensis is supralittoral wrack, but occasionally this species may be found living in, and feeding on, rotting driftwood as a secondary ecotope. Lower oxygen uptake rates were measured for driftwood-fed compared with wrack-fed P. platensis. The null hypothesis that the metabolic rate in P. platensis would remain unchanged after reversing the diet from driftwood to wrack was rejected. Diet reversal experiments demonstrated that the oxygen consumption rates of P. platensis were reversible and gradually attained. This is consistent with the change of diet from wrack to driftwood, or vice versa, causing physiological changes involving oxygen consumption in P. platensis, which are described as acclimation rather than adaptation.     

Differential responses of Nostoc sphaeroides and Arthrospira platensis to solar ultraviolet radiation exposure

During October to December 2003 we carried out experiments to assess the impact of high solar radiation levels (as normally occurring in a tropical region of Southern China) on the cyanobacteria Nostoc sphaeroides and Arthrospira (Spirulina) platensis. Two types of experiments were done: a) Short-term (i.e., 20 min) oxygen production of samples exposed to two radiation treatments (i.e., PAR+UVR—280–700 nm, and PAR only—400–700 nm, PAB and P treatments, respectively), and b) Long-term (i.e., 12 days) evaluation of photosynthetic quantum yield (Y) of samples exposed to three radiation treatments (i.e., PAB; PA (PAR+UV-A, 320–700 nm) and P treatments, respectively). N. sphaeroides was resistant to UVR, with no significant differences (P>0.05) in oxygen production within 20 min of exposure, but with a slight inhibition of Y within hours. A fast recovery of Y was observed after one day even in samples exposed to full solar radiation. A. platensis, on the other hand, was very sensitive to solar radiation (mainly to UV-B), as determined by oxygen production and Y measurements. A. platensis had a circadian rhythm of photosynthetic inhibition, and during the first six days of exposure to solar radiation, it varied between 80 and 100% at local noon, but cells recovered significantly during afternoon hours. There was a significant decrease in photosynthetic inhibition after the first week of exposure with values less than 50% at local noon in samples receiving full solar radiation. Samples exposed to PA and P treatments recovered much faster (within 2–3 days), and there were no significant differences in Y between the three radiation treatments when irradiance was low (late afternoon to early morning). Long-term acclimation seems to be important in A. platensis to cope with high UVR levels however, it is not attained through the synthesis of UV-absorbing compounds but it seems to be mostly related to adaptive morphological changes.     

A 'polarisation sun-dial' dictates the optimal time of day for dispersal by flying aquatic insects

1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood. 2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid‐morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid‐morning; (ii) in the evening; (iii) both in mid‐morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(θ) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (θ) for dark reflectors while P(θ) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(θ) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations θ. The θ‐dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid‐morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun‐dial’ of dispersing aquatic insects.     

Simultaneous use of sodium nitrate and urea as nitrogen sources improves biomass composition of Arthrospira platensis cultivated in a tubular photobioreactor

Arthrospira platensis is widely cultivated in open ponds for industrial purposes. However, high‐protein A. platensis biomass produced in photobioreactors (PBRs) is recommended for pharmaceutical and cosmetic formulations. A. platensis was cultivated in a 3.5 L tubular airlift PBR using both sodium nitrate and urea as nitrogen sources. Sodium nitrate was added from the start of the cultivation using a batch process. Urea was supplied daily at exponentially increasing feeding rate using a fed‐batch process. The simultaneous optimization of the independent variables, namely, total quantity of sodium nitrate (m_T1) and total quantity of urea (m_T2), led to an optimal condition of m_T1 = 15.0 mmol/L and m_T2 = 7.5 mmol/L. Maximum biomass concentration (5183 ± 94 mg/L) corresponding to the highest biomass productivity (683 ± 13 mg/L/day) was obtained under such condition. The addition protocol of both nitrogen sources resulted in high productivities of protein (6.2 ± 0.4 mg/L/day) as well as chlorophyll‐a (372.2 ± 7.7 mg/L/day). Such innovative process could be applied in the large‐scale production of A. platensis using tubular PBR for novel applications.     

Interplay of temperature and light influences wild guppy (Poecilia reticulata) daily reproductive activity

In this study we investigated the environmental regulation of daily reproductive activity of guppies (Poecilia reticulata). We observed male guppy reproductive behaviour for 17 days over three time periods (dawn, noon, and dusk) while recording natural variation in water temperature and light level. Water temperatures recorded during the experiments were highly variable (up to 7 °C per day), and there was a recurring pattern in daily variation for both light and temperature. Levels of activity were highest at dawn and similarly low during noon and dusk, but reproductive behaviour was recorded throughout the day. Mixed‐effects models indicate that light and temperature affect reproductive behaviour differently at different times of the day, and can also have opposing effects. We suggest that the environmental heterogeneity of streams in Trinidad has led to a broad thermal tolerance, and has contributed to the high level of phenotypic plasticity in the guppy and its success as an invasive species. Furthermore, our results show that daily variation in temperature and its interaction with light should be considered in future studies of guppy reproductive behaviour. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 511–520.     

Diurnal variations in physiology and behaviour of the noble crayfish Astacus astacus and the signal crayfish Pacifastacus leniusculus

Heart rate, locomotor activity, and oxygen consumption were recorded simultaneously and continuously in seven individuals of the noble crayfish Astacus astacus (Linneus 1758) and seven individuals of the signal crayfish Pacifastacus leniusculus (Dana 1852). The recordings were made in the laboratory over 7 days at 15°C under a 12?:?12?h dark?:?light regime. Circadian rhythms in heart rate, locomotor activity and oxygen consumption were found both in A. astacus and P. leniusculus. Increased heart rate, locomotor activity, and oxygen consumption levels during night time in both A. astacus and P. leniusculus illustrated expression of nocturnal behaviour. No differences in oxygen consumption levels were observed between A. astacus and P. leniusculus. Also, no significant difference between heart rate levels or heart rate variances was found in A. astacus and P. leniusculus at night. During day, however, heart rate levels, heart rate variances and locomotor activity were higher in P. leniusculus than in A. astacus. The higher activity level in P. leniusculus than in A. astacus during daytime indicates that P. leniusculus is less strictly nocturnal than is A. astacus.     

Triatominae in furnariid nests of the Argentine Gran Chaco

Triatomines (Hemiptera, Reduviidae) are bloodsucking insects involved in the transmission of Trypanosoma cruzi, the causative agent of Chagas disease, an important public health problem in Latin America. The triatomine species found in sylvatic habitats generally play a limited epidemiological role compared to domestic species, but they may act as a reinfestation source of dwellings after insecticide spraying and have to be carefully considered in control strategies of Chagas disease transmission. The objectives of this work were to carry out a survey of the sylvatic triatomine species colonizing Furnariidae nests in a typical area of the Chaco region of Argentina during the winter and to study the parasites and natural enemies associated with the collected triatomines. Sixty‐three triatomine specimens were collected from Furnariidae nests (Coryphistera alaudina and Phacellodomus sibilatrix) randomly selected within the study area. Fifty‐four were identified as Psammolestes coreodes, seven as Triatoma platensis, and two as Triatoma infestans. Specimens of T. infestans and T. platensis were found in one nest. The first finding of instar nymphs of T. infestans x T. platensis in a sylvatic habitat is reported. For the first time, sylvatic collected specimens of T. platensis were found infected by T. cruzi. Triatoma virus was found in one Ps. coreodes specimen.     

Photoadaptation, photoinhibition and productivity in the blue-green alga, Spirulina platensis grown outdoors

Two Spirulina platensis strains, SP-G and SP-RB, resistant and sensitive to photoinhibition of photosynthesis, respectively, were grown outdoors in dense cultures and under different photon fluxes provided by shading. Cultures of both strains grown under full sunlight were more resistant to photoinhibition than those grown under nets with 15–50% decreases in the incident photon flux. Cultures grown outdoors were more resistant to photoinhibition than the laboratory ones. At noon, the photosynthetic activity, as expressed by O₂ evolution, was higher for cultures grown under 50% shade, as compared with unshaded cultures. Productivity of the shaded cultures, in terms of biomass produced per day, was always higher when the cultures were protected from photoinhibition.     

Oxygen consumption rate in rotifers

The oxygen consumption rate (OCR) is a cumulative index of metabolic losses during aerobic metabolism. The generalized relationship of oxygen consumption rate (R, n1 O₂ ind^–1 h^–1) and dry body mass (M, µg) for rotifers is described by the equation: R = 9.15M^0.716. The level of rotifer metabolism is slightly lower than that of multicellular poikilothermic animals. Differences of OCR values in ontogenesis are substantial. Embryos and senile individuals are characterized by minimal OCR values. The OCR of oviparous females in the beginning of reproduction exceeds 2–3 times OCR values of juveniles. Differences in oxygen consumption intensity (OCI) are not so essential. OCR depends on food concentration. An increase of food concentration from 1.4 to 7.0 µg dry mass m1^–1 resulted in Brachionus calyciflorus in an OCR escalation of 2.5 times at 30°C, and 0.5 times at 25°C. Maximal OCR values occur at food concentration close to the saturation concentration for population growth rate. An exponential equation is adequate to describe R-t dependence for animals, long-term adapted to different constant temperatures (2 < Q₁₀ < 3). Acclimation effects observed during sharp temperature changes are determined by peculiarities of compensation reactions in species and separate populations. The formation of a zone of relative temperature independence of OCR (Q¹⁰ 1) at fluctuating temperature is observed. It is necessary to study enzymatic activities parallel to OCR and OCI measurements.     

An investigation of <Emphasis Type="Italic">Clostridium</Emphasis> species present in nutraceutical preparations of <Emphasis Type="Italic">Arthrospira platensis</Emphasis> (<Emphasis Type="Italic">Spirulina</Emphasis>) for human consumption

The presence of the anaerobic spore former Clostridium in Arthrospira platensis destined for human consumption is generally not assessed during quality assurance procedures. As this nutraceutical is administered as complementary medicine to the immunocompromised, this study aimed to investigate the presence of these potential pathogens. Anaerobic counts performed on tablets from a single manufacturer indicated an excess of 10⁵ CFU/endospores g⁻¹ tablet for three different A. platensis batches. Tests for coliforms for use as “indicators” of pathogens in the tablets were negative. Using classic culture techniques, five species of Clostridium were isolated. Subsequent use of PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting of tablets showed a divergent microbial population, with a predominance of anaerobic endospore formers, including Clostridium. Sequencing of a 1.5 kb 16S rDNA clone library and phylogenetic analyses of prominent operational taxonomic units confirmed the presence of an additional five Clostridium spp. and other genera in the tablets. A composite molecular ladder, using 16S rRNA DGGE amplicons of 17 representative bacterial species was constructed to assist in identifying anaerobes present in tablets sourced from three different A. platensis manufacturers. Results indicated that commercial A. platensis preparations were contaminated with potentially hazardous clostridia and other anaerobic species. Results suggest that certain commercial A. platensis preparations require stringent microbial quality assurance measures to ensure safe use as a nutraceutical for the immunocompromised and the general public.     

Lipopolysaccharide-induced alterations in oxygen consumption and radical generation in endothelial cells

Oxygen consumption rate (OCR) and generation of superoxide and nitric oxide (NO) in mouse aortic endothelial cells (MAECs) treated with lipopolysaccharide (LPS) were studied. The OCR was determined in cell suspensions at 37 °C by electron paramagnetic resonance (EPR) spectroscopy. LPS significantly altered the OCR in a dose and time-dependent fashion. The OCR was significantly elevated immediately following the treatment of MAECs with LPS (5 and 10 μg/ml) and NADPH (100 μM) whereas the same was depressed 1 h after exposure to similar conditions of incubation. Under similar experimental conditions, superoxide generation was also determined by EPR spectroscopy and cytochrome c reduction assays. A marginal increase in the superoxide production was observed when the cells were treated with LPS and NADPH alone whereas the same was further enhanced significantly when the cells were treated with LPS and NADPH together. The increase in oxygen consumption and superoxide production caused by LPS was inhibited by diphenyleneiodonium (DPI), suggesting the involvement of NAD(P)H oxidase. A significant increase in the NO production by MAECs was noticed 1 h after treatment with LPS and was inhibited by L-NAME, further suggesting the involvement of nitric oxide synthase (NOS). Thus, on a temporal scale, LPS-induced alterations in oxygen consumption by MAECs may be under the control of dual regulation by NAD(P)H oxidase and NOS. (Mol Cell Biochem 278: 119–127, 2005)     

Isolation,characterization and localization of extracellular polymeric substances from the cyanobacterium Arthrospira platensis strain MMG-9

Arthrospira platensis is a cyanobacterium known for its nutritional value and secondary metabolites. Extracellular polymeric substances (EPS) are an important trait of most cyanobacteria, including A. platensis. Here, we extracted and analysed different fractions of EPS from a locally isolated strain of A. platensis. Three different fractions of EPS were distinguished. These were EPS released into the medium (REPS), EPS loosely bound to the organism (LEPS) and EPS tightly bound to the organism (TEPS), which were extracted by different procedures. The LEPS fraction was smaller than the other two fractions. The EPS of A. platensis exhibited high diversity. Total protein and carbohydrate content was determined in each of these fractions. The largest amount of total carbohydrates and total proteins was in the TEPS fraction. Eight sugar moieties were detected and analysed in all EPS fractions using HPAE-PAD. Fructose, mannose and ribose were rare sugar residues in all fractions of EPS. With the exception of fructose, all sugars tested for were detected in TEPS. The amount of sugars detected was significantly higher in TEPS compared with the two other fractions, especially for galactose, xylose and glucose. The EPS were localized by confocal laser scanning microscopy (CLSM) after staining with different fluorescent dyes and it was found that A. platensis possessed a thick and smooth layer of EPS around the spiral trichomes.     

A novel process for the production of high-purity galactooligosaccharides (GOS) using consortium of microbes

Galactooligosaccharides (GOS) are nondigestible dietary fibers which have a beneficial effect on human health by promoting the growth of probiotic bacteria in the gut. In addition, other health benefits have been reported from oligosaccharides consumption such as stimulation of intestinal mobility, colon cancer prevention, mineral absorption as well as protection against certain pathogenic bacterial infections. The goal of this research was to develop an efficient biotransformation system using a consortium of microbes for the production of ≥85% pure GOS and reusing the cell biomass in repeated cycles of biotransformation. Production of GOS by lactose transgalactosylation using whole cells of Sporobolomyces singularis MTCC 5491 as a source of β-galactosidase and monosaccharides utilization by yeast isolate (NUTIDY007) were studied. For increasing the purity of GOS, growth and bioconversion parameters on the transgalactosylation by the whole cells were investigated. Further, continuous production of GOS was studied in a reactor with microfiltration membrane system. A maximum GOS purity of 42% was achieved using single culture of S. singularis. Under optimized conditions, single culture of S. singularis produced a maximum of 56% pure GOS. Addition of second culture to the reaction mixture for utilization of glucose significantly increased the GOS purity from 56% to ≥85%. The product consisted of tri- to penta-galactooligosaccharides. Trisaccharides were the main component of the reaction mixture. A maximum productivity of 10.9?g/L/hr was obtained under the optimum conditions.     

Some factors affecting the respiration of some aquatic plants

Summary The oxygen consumption of four aquatic plants has been determined at various concentrations of dissolved oxygen and at three different temperatures.Oxygen consumption rates (mg oxygen/g dry weight per hr) at 20°C in air-saturated water were Berula erecta, 1.25; Callitriche obtusangula, 2.8; Hippuris vulgaris, 1.96; and Ranunculus pseudofluitans, 1.90.Oxygen consumption rates increased with increase in dissolved-oxygen concentration within the experimental limits of 1.2–17 p.p.m. dissolved oxygen. The relation of oxygen consumption to this range of oxygen concentrations can be described by the empirical equation R = aC ^b. Increase of temperature has been shown to increase the rates of oxygen consumption. Q₁₀ values ranging from 1.32 to 3.48 have been obtained.     

Effects of dietary whole and defatted Arthrospira platensis (Cyanobacterium) on growth,body composition and pigmentation of the yellow catfish Pelteobagrus fulvidraco

The cyanobacterium Arthrospira platensis is regarded as a potential future source of food for humans due to its superior nutritional value compared with many conventional crops. An 8-week feeding trial was conducted to evaluate nutritional and pigmentation effects of whole A. platensis, defatted A. platensis and its lipid extracts in diets for the yellow catfish Pelteobagrus fulvidraco. Four percent whole A. platensis (AP4), 0.4% A. platensis lipid extracts (AL0.4), and 4% defatted A. platensis (AR4) were used as experimental diets, and a diet without any A. platensis was as the control diet (AP0). The AP4 and AL0.4 groups had no effects on the growth performance and feed utilization in yellow catfish; however, the AR4 group was significantly lower than the AP0 group in terms of specific growth rate and feed efficiency (P < 0.05). AP4 and AL0.4 groups significantly increased the body protein of fish (P < 0.05). The skin color was significantly improved in the AP4 and AL0.4 groups, as well as the fish skin and plasma lutein contents (P < 0.05). Correlations between skin color and the lutein contents in liver and muscles were weak, whereas the correlations between skin color and the lutein contents in skin and plasma were significant and strong. The results suggest that whole A. platensis and its lipid extracts can be functional additives to improve whole body protein and skin color of fish, while defatted A. platensis showed no advantage in yellow catfish diets.

     

Aggressive encounters differentially affect serum dehydroepiandrosterone and testosterone concentrations in male Siberian hamsters (Phodopus sungorus)

The gonadal hormone testosterone (T) regulates aggression across a wide range of vertebrate species. Recent evidence suggests that the adrenal prohormone dehydroepiandrosterone (DHEA) may also play an important role in regulating aggression. DHEA can be converted into active sex steroids, such as T and estradiol (E₂), within the brain. Previous studies show that circulating DHEA levels display diurnal rhythms and that melatonin increases adrenal DHEA secretion in vitro. Here we examined serum DHEA and T levels in long-day housed Siberian hamsters (Phodopus sungorus), a nocturnal species in which melatonin treatment increases aggression. In Experiment 1, serum DHEA and T levels were measured in adult male hamsters during the day (1200 h, noon) and night (2400 h, midnight). In Experiment 2, aggression was elicited using 5-min resident–intruder trials during the day (1800 h) and night (2000 h) (lights-off at 2000 h). Serum DHEA and T levels were measured 24 h before and immediately after aggressive encounters. In Experiment 1, there was no significant difference in serum DHEA or T levels between noon and midnight, although DHEA levels showed a trend to be lower at midnight. In Experiment 2, territorial aggression was greater during the night than the day. Moreover, at night, aggressive interactions rapidly decreased serum DHEA levels but increased serum T levels. In contrast, aggressive interactions during the day did not affect serum DHEA or T levels. These data suggest that nocturnal aggressive encounters rapidly increase conversion of DHEA to T and that melatonin may play a permissive role in this process.     

Cytogenetic Analysis of Experimental Hybrids in Species of Triatominae (Hemiptera-Reduviidae)

A cytogenetic analysis was performed in experimental hybrids between species of Chagas disease transmitting bugs with remarkable differences in the amount and distribution of heterochromatin. Using C-banding technique, we identified the parental species chromosomes and analysed the meiotic behaviour in the male hybrids between Triatoma platensis and T. infestans, T. platensis and T. delpontei, and T. infestans and T. rubrovaria. The two former hybrids have an entirely normal meiotic behaviour despite the extensive differences in C-banded karyotypes observed in the parental species, indicating that heterochromatin differences between homeologous chromosomes are not a barrier that influences meiotic synapsis and recombination. On the contrary, the experimental hybrids between T. infestans and T. rubrovaria show failures in pairing of homeologous chromosomes that lead to the production of abnormal spermatids and hybrid sterility. Our data suggest that karyotypic repatterning within triatomines has involved at least two different pathways. Among closely related species, chromosomal changes have largely involved addition or deletion of heterochromatic regions. In more distant species, chromosomal rearrangements (i.e. inversions and translocations) have also arisen. Hybridisation data also allow to hypothesize about the origin and divergence of this taxonomic group, as well as the mechanisms that maintain species isolation.     

西施舌的耗氧率与排氨率研究

采用室内实验生态学方法研究了不同栖息水温和不同溶解氧水平下处于标准代谢状态的西施舌耗氧率与排氨率,并测定了窒息点.结果表明,在25 ℃时,水中DO≥3.11±0.15 mg·L^-1时,西施舌的耗氧率和排氨率分别为0.7±0.05 mg·g^-1·h^-1和2.56±0.05 μmol·g^-1·h^-1,处于相对稳定状态;当DO低于此值则代谢出现异常,耗氧率随DO下降而下降,直到窒息为止,其窒息点为1.22±0.06 mg·L^-1,而排氨率也呈直线下降,但排氨停止滞后于耗氧停止.耗氧率与栖息水温呈二次线型关系:OCR=-0.0027T²+0.1367T-0.9557,R²=0.972;水温为25.3 ℃时,西施舌的耗氧率达到最大,为0.77 mg·g^-1·h^-1.处于适温状态(15 ℃和20 ℃)的O/N值要高于低温(10 ℃)和高温(25 ℃和30 ℃)时的O/N值,西施舌在适宜条件下更多地依赖于脂肪供能维持标准代谢,而在环境不适时则更多地调用机体的蛋白质来维持生理代谢需要.     

Feeding styles of five species of bottom-feeding fishes of the high Paraná river

Synopsis In this study the diets of five species of bottom-feeding fishes (Prochilodus lineatus, Steindachnerina insculpta, Loricariichthys platymetopon, Trachydoras paraguayensis and Iheringichthys labrosus) were analyzed. Samples were taken in the High Paraná River basin and its floodplain from August 1987 to July 1988 and in February, August and September 1991. The results demonstrated that P. lineatus and S. insculpta were ileophagous, L. platymetopon was detritivorous and I. labrosus and T. paraguayensis were benthophagous. The feeding activity was higher during the flood period for P. lineatus and in dry season for T. paraguayensis. P. lineatus and S. insculpta fed mainly during the day, while I. labrosus and T. paraguayensis during the day and dusk, respectively.     

Influence of Cell Detachment on the Respiration Rate of Tumor and Endothelial Cells

Cell detachment is a procedure routinely performed in cell culture and a necessary step in many biochemical assays including the determination of oxygen consumption rates (OCR) in vitro. In vivo, cell detachment has been shown to exert profound metabolic influences notably in cancer but also in other pathologies, such as retinal detachment for example. In the present study, we developed and validated a new technique combining electron paramagnetic resonance (EPR) oximetry and the use of cytodex 1 and collagen-coated cytodex 3 dextran microbeads, which allowed the unprecedented comparison of the OCR of adherent and detached cells with high sensitivity. Hence, we demonstrated that both B16F10 melanoma cells and human umbilical vein endothelial cells (HUVEC) experience strong OCR decrease upon trypsin or collagenase treatments. The reduction of cell oxygen consumption was more pronounced with a trypsin compared to a collagenase treatment. Cells remaining in suspension also encounter a marked intracellular ATP depletion and an increase in the lactate production/glucose uptake ratio. These findings highlight the important influence exerted by cell adhesion/detachment on cell respiration, which can be probed with the unprecedented experimental assay that was developed and validated in this study.