In Vitro CuIture of the Tropical Sponge <Emphasis Type="Italic">Axinella corrugata</Emphasis> (Demospongiae): Effect of Food Cell Concentration on Growth,Clearance Rate,and Biosynthesis of Stevensine

In vitro culture is one possible method for supplying sponge metabolites for pharmaceutical applications, but appropriate feeding regimens that maximize both growth and metabolite biosynthesis are largely unknown. According to the natural concentration (NC) of cells 1 to 50 µm in size that are available to wild Axinella corrugata, we fed explants a multispecific diet of bacteria, microalgae, and yeast at 4 different concentrations: 1NC, 3NC, 5NC, and 5+1NC (the last consisted of 5 NC of bacteria and 1 NC of microalgae and yeast). Explants fed a 3NC diet had the best culture response, growing on average from 8.5 g to 10.3 g in 8 weeks, and showing a 110% increase in concentration (milligrams per gram of dry weight) of the antitumor compound stevensine. Stevensine production in 3NC explants, representing the total milligrams of metabolite per explant, increased by 157% over the study. Explants fed at 1NC had relatively stable weights, indicating that the diet met metabolic costs only. Explants fed at the two highest concentrations lost weight after 4 weeks, possibly because long-term high cell concentration blocked their aquiferous system, reducing their ability to feed efficiently. Stevensine production in explants fed the 1NC, 5NC, or 5+1NC diets were similar, and varied little from the initial amount. A separate experiment showed that the clearance rate for A. corrugata is similar between the examined food types and cell concentrations over 5 hours, averaging 766 ml h^–1 g DW^–1.Overall, this study demonstrates that relatively small changes in food abundance can greatly affect both sponge growth and metabolite biosynthesis. The good growth and increased production of the target metabolite stevensine for A. corrugata explants fed a 3NC diet suggests that in vitro culture is a viable method of supplying some sponge metabolites.     

Efficiencies and costs of larval growth in different food environments (Asteroidea: Asterina miniata)

The ocean is a nutritionally heterogeneous environment. For feeding larval forms, food variability has significant consequences for growth and later recruitment success. In this study, the physiological and biochemical responses to a range of different food concentrations (unfed, 4, 20, and 40 algal cells μl^− 1) were examined in larvae of the asteroid, Asterina miniata. Measurements of growth, protein synthesis rates, and the energetic cost of protein synthesis were made. Under conditions of rapid growth, protein comprised a larger percent (66%) of a larva's organic biomass compared to similar-aged, slower-growing larvae (26%). Larvae fed at the highest food concentration tested (40 algal cells μl^− 1) had a protein depositional efficiency of 80% (± 16%), a value 3-fold higher than larvae fed 20 algal cells μl^− 1 (28% ± 11%). Also, faster-growing larvae required 3-fold less energy per unit mass of protein growth. Larvae fed 40 algal cells μl^− 1 deposited protein at a respiratory cost of 65 ± 11 pmol O₂ h^− 1 (μg protein)^− 1; larvae fed 20 algal cells μl^− 1 had a cost of 192 ± 47 pmol O₂ h^− 1 (μg protein)^− 1. While there were differences in the cost to deposit protein (i.e., protein growth, the balance of synthesis and degradation), there were no differences in the energetic cost of protein synthesis for all food concentrations tested. The energetic cost of protein synthesis was fixed at 13.8 (± 0.92) Joules (mg protein synthesized)^− 1 and was independent of developmental stage, growth rates, and large changes (58-fold) in protein synthesis rates. A major conclusion from this study is that larvae grown in high-food environments not only grew faster, but did so for considerably less energy. Defining the complex relationships of food availability and metabolic efficiency will provide more accurate predictions of larval growth under variable food conditions in the ocean.     

Vertical tubular photobioreactor for semicontinuous culture of Cyanobium sp

We evaluated the kinetic culture characteristics of the microalgae Cyanobium sp. grown in vertical tubular photobioreactor in semicontinuous mode. Cultivation was carried out in vertical tubular photobioreactor for 2 L, in 57 d, at 30 °C, 3200 Lux, and 12 h light/dark photoperiod. The maximum specific growth rate was found as 0.127 d⁻¹, when the culture had blend concentration of 1.0 g L⁻¹, renewal rate of 50%, and sodium bicarbonate concentration of 1.0 g L⁻¹. The maximum values of productivity (0.071 g L⁻¹ d⁻¹) and number of cycles (10) were observed in blend concentration of 1.0 g L⁻¹, renewal rate of 30%, and bicarbonate concentration of 1.0 g L⁻¹. The results showed the potential of semicontinuous cultivation of Cyanobium sp. in closed tubular bioreactor, combining factors such as blend concentration, renewal rate, and sodium bicarbonate concentration.     

Nitrogen nutrition of Canna indica: Effects of ammonium versus nitrate on growth, biomass allocation, photosynthesis, nitrate reductase activity and N uptake rates

The effects of inorganic nitrogen (N) source (NH₄⁺, NO₃⁻ or both) on growth, biomass allocation, photosynthesis, N uptake rate, nitrate reductase activity and mineral composition of Canna indica were studied in hydroponic culture. The relative growth rates (0.05-0.06 g g⁻¹ d⁻¹), biomass allocation and plant morphology of C. indica were indifferent to N nutrition. However, NH₄⁺ fed plants had higher concentrations of N in the tissues, lower concentrations of mineral cations and higher contents of chlorophylls in the leaves compared to NO₃⁻ fed plants suggesting a slight advantage of NH₄⁺ nutrition. The NO₃⁻ fed plants had lower light-saturated rates of photosynthesis (22.5 μmol m⁻² s⁻¹) than NH₄⁺ and NH₄⁺/NO₃⁻ fed plants (24.4-25.6 μmol m⁻² s⁻¹) when expressed per unit leaf area, but similar rates when expressed on a chlorophyll basis. Maximum uptake rates (V_max) of NO₃⁻ did not differ between treatments (24-35 μmol N g⁻¹ root DW h⁻¹), but V_max for NH₄⁺ was highest in NH₄⁺ fed plants (81 μmol N g⁻¹ root DW h⁻¹), intermediate in the NH₄NO₃ fed plants (52 μmol N g⁻¹ root DW h⁻¹), and lowest in the NO₃⁻ fed plants (28 μmol N g⁻¹ root DW h⁻¹). Nitrate reductase activity (NRA) was highest in leaves and was induced by NO₃⁻ in the culture solutions corresponding to the pattern seen in fast growing terrestrial species. Plants fed with only NO₃⁻ had high NRA (22 and 8 μmol NO₂⁻ g⁻¹ DW h⁻¹ in leaves and roots, respectively) whereas NRA in NH₄⁺ fed plants was close to zero. Plants supplied with both forms of N had intermediate NRA suggesting that C. indica takes up and assimilate NO₃⁻ in the presence of NH₄⁺. Our results show that C. indica is relatively indifferent to inorganic N source, which together with its high growth rate contributes to explain the occurrence of this species in flooded wetland soils as well as on terrestrial soils. Furthermore, it is concluded that C. indica is suitable for use in different types of constructed wetlands.     

Feeding response of the polychaete Sabellaria alveolata (Sabellariidae) to changes in seston concentration

Sabellaria alveolata is a tube-building gregarious polychaete that constructs large biogenic reefs. In macrotidal shellfish ecosystems, this species competes for food with cultivated suspension-feeders. The suspension-feeding activity and clearance rate of S. alveolata were investigated in response to changes in seston concentration. A flow-through system was designed to study 225 cm² reef blocks with more than 500 individuals. The experimental conditions were characterized by increasing concentrations of suspended particulate matter ranging from 6.5 to 153.8 mg L⁻¹, while the organic content of the diet (microalgae Skeletonema costatum) decreased inversely from 49 to 9%, to mimic the dilution of organic matter by inorganic particles, characteristic of tidal resuspension. We showed that the clearance rate exponentially decreased in relation to an increase in SPM concentration. Clearance rate was estimated at 5.3 10^− 3 L h^− 1 or 0.93 L h^− 1 g^− 1 (dry weight) for the lowest seston concentration (SPM = 6.5 mg L^− 1) and reached the asymptote at CR = 1.97 10^− 3 L h^− 1 or 0.35 L h^− 1 g^− 1 (dry weight) when SPM exceeded 45 mg L^− 1. Using picture analyses of polychaete movements, we showed that, paradoxically, an increase in SPM concentration did not adversely affect the feeding activity of S. alveolata since the number of filtering individuals remained stable from SPM = 6.5 to 55.5 mg L^− 1. These values were applied at the scale of the bay of Mont-Saint-Michel (France) to demonstrate that the filtration pressure of large populations of wild suspension-feeders should not be underestimated when the carrying capacity has to be assessed in the context of increasing bivalve cultures.     

Local bioprospecting for high-lipid producing microalgal strains to be grown on concentrated municipal wastewater for biofuel production

Mass cultivation of microalgae for biofuel production depends heavily on the performance of the microalgae strains used. In this study, 60 algae-like microorganisms collected from different sampling sites in Minnesota were examined using multi-step screening and acclimation procedures to select high-lipid producing facultative heterotrophic microalgae strains capable of growing on concentrated municipal wastewater (CMW) for simultaneous energy crop production and wastewater treatment. Twenty-seven facultative heterotrophic microalgae strains were found, among which 17 strains were proved to be tolerant to CMW. These 17 top-performing strains were identified through morphological observation and DNA sequencing as Chlorella sp., Heynigia sp., Hindakia sp., Micractinium sp., and Scenedesmus sp. Five strains were chosen for other studies because of their ability to adapt to CMW, high growth rates (0.455-0.498 d⁻¹) and higher lipid productivities (74.5-77.8 mg L⁻¹ d⁻¹). These strains are considered highly promising compared with other strains reported in the literature.     

Accumulation and excretion of morphine by Calliphora stygia, an Australian blow fly species of forensic importance

This study examined the ability of the forensically important blow fly, Calliphora stygia to actively excrete morphine, thereby maintaining a low morphine level within its body when fed on a diet containing morphine at low (7 pmol g⁻¹) and high (17.5 pmol g⁻¹) concentrations. Morphine was accumulated within the bodies of maggots (≈70% within the tissues) at concentrations which were lower than that of the meat (3-24%). The morphine content of the initial developing stages (second and third instar maggots) maintained on the high morphine diet was higher than those on the low morphine diet. Morphine was cleared from the body with negatively exponential kinetics (High morphine group: Morphine (pmol g⁻¹ wet weight) = 8425e^−0.014t. Low morphine group: Morphine (pmol g⁻¹ wet weight) = 2180e^−0.010t). Clearance constants for morphine by animals in both groups were similar and thus both groups had a similar ability to excrete morphine. The Malpighian tubules of maggots were able to actively secrete morphine using a transport mechanism that transports small type II organic cations, such as morphine and quinine. The rate of morphine secretion by the Malpighian tubules could explain the clearance of the drug by the maggots. As the morphine was transported across the Malpighian tubules cells, a significant proportion was metabolised into a compound that is yet to be fully characterised.     

Increased lipid production of the marine oleaginous microalgae Isochrysis zhangjiangensis (Chrysophyta) by nitrogen supplement

Effects of nitrate feeding on the cell growth and lipid accumulation of marine microalgae Isochrysis zhangjiangensis were investigated. When nitrate was supplied at interval of 24 h, instead of 72 h, a high lipid content of 40.9% and a biomass density of 3.1 g L⁻¹ were obtained. To confirm whether I. zhangjiangensis accumulates lipid during nitrogen-repletion, a two-stage cultivation method was applied. This algal strain had a high lipid content during sustained nitrate addition and showed a high carbohydrate content under nitrate-depletion conditions. These results revealed that this algal strain can accumulate lipids under nitrogen-repletion conditions and accumulate carbohydrate under nitrogen-depletion conditions. When cultured in an extremely high nitrate concentration, 9 g L⁻¹ at 24 h intervals, the growth of algal cells was suppressed, but the highest lipid content of 53% was attained. This special characteristic of lipid accumulation makes I. zhangjiangensis an ideal candidate for producing biodiesel using N-rich wastewater.     

Multi-objective optimization of glycopeptide antibiotic production in batch and fed batch processes

Fermentation optimization involves potentially conflicting multiple objectives such as product concentration and production media cost. Simultaneous optimization of these objectives would result in a multiobjective optimization problem, which is characterized by a set of multiple solutions, knows as pareto optimal solutions. These solutions gives flexibility in evaluating the trade-offs and selecting the most suitable operating policy. Here, ε-constraint approach was used to generate the pareto solutions for two objectives: product concentration and product per unit cost of media, for batch and fed batch operations using process model for Amycolatopsis balhimycina, a glycopeptide antibiotic producer. This resulted in a set of several pareto optimal solutions with the two objectives ranging from (0.75 g l⁻¹, 3.97 g $^-1) to (0.44 g l⁻¹, 5.19 g $^-1) for batch and from (1.5 g l⁻¹, 5.46 g $^-1) to (1.1 g l⁻¹, 6.34 g $^-1) for fed batch operations. One pareto solution each for batch and for fed batch mode was experimentally validated.     

Effects of Bacillus thuringiensis toxin Cry1Ac and cytoplasmic polyhedrosis virus of Helicoverpa armigera (Hübner) (HaCPV) on cotton bollworm (Lepidoptera: Noctuidae)

In this study, interactions on the mortality and debilitating effects between Cry1Ac, a toxic protein produced by Bacillus thuringiensis (Berliner) and HaCPV (Chinese strain) on first and third instars larvae of Helicoverpa armigera were evaluated in laboratory. When first instar was exposed to combination of Bt cotton leaf discs containing HaCPV (6 × 10⁶, 1 × 10⁷, and 3 × 10⁷ PIB ml⁻¹) the effect on mortality was additive, when such instar larvae exposed to combination of Cry1Ac (0.9, 2.7, or 8.1 μg g⁻¹) and the same concentrations of HaCPV the effect on mortality was additive except for the combination of Cry1Ac (0.3 μg g⁻¹) and HaCPV concentrations that showed synergism. When third instars of H. armigera were infected using a suspension containing both HaCPV and Cry1Ac, most combinations of them showed additive effect except for the combination of Cry1Ac (0.3 μg g⁻¹) and HaCPV (3 × 10⁷ PIB ml⁻¹) that showed synergism. However, when they exposed to Bt cotton leaf discs and HaCPV the effect on mortality was synergism except combination of Bt cotton leaf discs and HaCPV (6 × 10⁶ PIB ml⁻¹) that showed additive. Most of the combinations are showed additive effect in the toxicity and in combinations of Cry1Ac at lowest and HaCPV at highest concentrations synergism is observed. Not only were larval growth and development delayed, but pupation and pupal weight also decreased when larvae were fed on artificial diet containing Cry1Ac and HaCPV or transgenic Bt cotton leaf discs specially in first instar.     

Assessment of olive-mill wastewater as a growth medium for lipase production by Candida cylindracea in bench-top reactor

Olive-mill wastewater (OMW) was investigated for its suitability to serve as a medium for lipase production by Candida cylindracea NRRL Y-17506. The OMW that best supported enzyme production was characterized by low COD and low total sugars content. In shake flask batch cultures, OMW supplementation with 2.4 g l⁻¹ NH₄Cl and 3 g l⁻¹ olive oil led to an enzyme activity of about 10 U ml⁻¹. The addition of glucose or malt extract and supplements containing organic N (e.g., peptone, yeast extract) either depressed or did not affect the enzyme production. Further experiments were then performed in a 3-l stirred tank reactor to assess the impact of medium pH and stirring speed on the yeast enzyme activity. The lipase activity was low (1.8 U ml⁻¹) when the pH was held constant at 6.5, significantly increased (18.7 U ml⁻¹) with uncontrolled pH and was maximum (20.4 U ml⁻¹) when the pH was let free to vary below 6.5. A stirring regime, that varied depending on the dissolved oxygen concentration in the medium, both prevented the occurrence of anoxic conditions during the exponential growth phase and enabled good lipase production (i.e., 21.6 U ml⁻¹) and mean volumetric productivity (i.e., 123.5 U l⁻¹ h⁻¹).     

The kinetics of the hydrogen/deuterium exchange of epidermal growth factor receptor ligands

Five highly homologous epidermal growth factor receptor ligands were studied by mass spectral analysis, hydrogen/deuterium (H/D) exchange via attenuated total reflectance Fourier transform-infrared spectroscopy, and two-dimensional correlation analysis. These studies were performed to determine the order of events during the exchange process, the extent of H/D exchange, and associated kinetics of exchange for a comparative analysis of these ligands. Furthermore, the secondary structure composition of amphiregulin (AR) and heparin-binding-epidermal growth factor (HB-EGF) was determined. All ligands were found to have similar contributions of 3₁₀-helix and random coil with varying contributions of β-sheets and β-turns. The extent of exchange was 40%, 65%, 55%, 65%, and 98% for EGF, transforming growth factor-α (TGF-α), AR, HB-EGF, and epiregulin (ER), respectively. The rate constants were determined and classified as fast, intermediate, and slow: for EGF the 0.20 min⁻¹ (Tyr), 0.09 min⁻¹ (Arg, β-turns), and 1.88 × 10⁻³ min⁻¹ (β-sheets and 3₁₀-helix); and for TGF-α 0.91 min⁻¹ (Tyr), 0.27 min⁻¹ (Arg, β-turns), and 1.41 × 10⁻⁴ min⁻¹ (β-sheets). The time constants for AR 0.47 min⁻¹ (Tyr), 0.04 min⁻¹ (Arg), and 1.00 × 10⁻⁴ min⁻¹ (buried 3₁₀-helix, β-turns, and β-sheets); for HB-EGF 0.89 min⁻¹ (Tyr), 0.14 min⁻¹ (Arg and 3₁₀-helix), and 1.00 × 10⁻³ min⁻¹ (buried 3₁₀-helix, β-sheets, and β-turns); and for epiregulin 0.16 min⁻¹ (Tyr), 0.03 min⁻¹ (Arg), and 1.00 × 10⁻⁴ min⁻¹ (3₁₀-helix and β-sheets). These results provide essential information toward understanding secondary structure, H/D exchange kinetics, and solvation of these epidermal growth factor receptor ligands in their unbound state.     

Comparison of polysialic acid production in Escherichia coli K1 during batch cultivation and fed-batch cultivation applying two different control strategies

The polysialic acid (PSA) production in Escherichia coli (E. coli) K1 was studied using three different cultivation strategies. A batch cultivation, a fed-batch cultivation at a constant specific growth rate of 0.25 h⁻¹ and a fed-batch cultivation at a constant glucose concentration of 50 mg l⁻¹ was performed. PSA formation kinetics under different cultivation strategies were analyzed based on the Monod growth model and the Luedeking-Piret equation. The results revealed that PSA formation in E. coli K1 was completely growth associated, the highest specific PSA formation rate (0.0489 g g⁻¹ h⁻¹) was obtained in the batch cultivation. However, comparing biomass and PSA yields on the glucose consumed, both fed-batch cultivations provided higher yields than that of the batch cultivation and acetate formation was prevented. Moreover, PSA yield on glucose was also correlated to the specific growth rate of the cells. The optimal specific growth rate for PSA production was 0.32 h⁻¹ obtained in the fed-batch cultivation at a constant glucose concentration of 50 mg l⁻¹, with highest conversion efficiency of 43 mg g⁻¹.     

Zinc incorporation in the otoliths of juvenile pink snapper (Pagrus auratus Forster): The influence of dietary versus waterborne sources

Separate laboratory experiments were conducted to examine if incorporation of Zn into the otoliths of juvenile pink snapper (Pagrus auratus Forster) was related to levels in the food and/or water. In the first experiment, fish were fed a regular diet (600 mg Zn kg^− 1 dw, control group) or a Zn-enriched diet (6000 mg Zn kg^− 1 dw or 9000 mg Zn kg^− 1 dw) for 35 days. In the second experiment, fish were exposed to waterborne Zn concentrations of < 0.005 µg L^− 1 (control), 50 µg L^− 1, 100 µg L^− 1 and 200 µg L^− 1 for 35 days. The sagittal otoliths were analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Juvenile fish exposed to higher concentrations of waterborne Zn did not display increased Zn levels in their otoliths. However, Zn levels in the otoliths of fish consuming the Zn-enriched diet were significantly higher relative to control fish. This study clearly demonstrated that dietary Zn was the major source of Zn incorporated into the otoliths by this marine fish.     

Effects of Bacillus thuringiensis toxin Cry1Ac and Beauveria bassiana on Asiatic corn borer (Lepidoptera: Crambidae)

In this study, interactions between Cry1Ac, a toxic crystal protein produced by Bacillus thuringiensis (Berliner), and Beauveria bassiana on the mortality and survival of Ostrinia furnacalis was evaluated in the laboratory. The results showed that Cry1Ac is toxic to O. furnacalis. Not only were larval growth and development delayed, but pupation, pupal weight and adult emergency also decreased when larvae were fed on artificial diet containing purified Cry1Ac toxin. When third instars O. furnacalis were exposed to combination of B. bassiana (1.8 × 10⁵, 1.8 × 10⁶ or 1.8 × 10⁷ conidia ml⁻¹) and Cry1Ac, (0.2 or 0.8 μg g⁻¹), the effect on mortality was additive, however, the combinations of sublethal concentrations showed antagonism between Cry1Ac (3.2 or 13 μg g⁻¹) and B. bassiana (1.8 × 10⁵ or 1.8 × 10⁶ conidia ml⁻¹). When neonates were reared on sublethal concentrations of Cry1AC until the third instar, and survivors exposed B. bassiana conidial suspension, such treatments showed additive effect on mortality of O. furnacalis except for the combination of Cry1Ac (0.2 μg g⁻¹) and B. bassiana (1.8 × 10⁶ conidia ml⁻¹) that showed antagonism.     

The paradox high zooplankton biomass-low vegetal particulate organic matter in high turbidity zones: What way for energy transfer?

Estuarine ecosystems are characterized by high zooplanktonic biomasses, essentially constituted by copepods and mysids whose nutritional requirements are mainly provided by phytoplankton, an easily available carbon form. The Gironde estuary is characterized by high turbidities which limit light penetration in the water column and therefore primary production. Consequently, primary production is low and its availability for higher trophic level is very limited. The main goal of this study was to characterize the total vegetal particulate organic matter (POM) in high turbidity zones of the Gironde estuary during summer (a critical period characterized by high heterotrophic bacterial degradation and high zooplanktonic biomasses) and to analyse its utilization by zooplankton, using prey/predator experiments and trophic biomarkers (fatty acids). The specific goals were to define (i) how vegetal POM was exploited by the different zooplanktonic groups (protozoa, copepods and mysids) and (ii) which alternative preys could be used when vegetal POM was not sufficient to ensure their nutritional requirements.Chlorophyll biomass was very low in the MTZ during summer 2002 (0.48 ± 0.03 mg m^− 3). Total zooplankton grazing was low (19% d^− 1) probably due to a large contribution of detritus originating from terrestrial plants in vegetal POM compared to phytoplankton. The highest grazing pressure was exercised by the mysid Mesopodopsis slabberi due to its high abundances and by its almost entirely herbivorous diet (phytoplankton and small terrestrial detritus). Grazing rates (19.7 ± 4.2 and 9.6 μgC cop^− 1 d^− 1 for juveniles and adults, respectively) seemed to be sufficient to satisfy their daily carbon requirement. Grazing rate of the copepod Eurytemora affinis (139 ngC cop^− 1 d^− 1) seemed to be insufficient to cover its nutritional requirements and the copepods probably needed to complete a great part of their diet from protozoa. Grazing rates of the mysid Neomysis integer (24.7 ± 0.01 and 20.89 ± 8.45 μgC cop^− 1 d^− 1 for juveniles and adults, respectively) were higher than those of M. slabberi when feeding only on phytoplankton. However, when other preys were introduced in its environment, N. integer only fed on the copepod E. affinis with a preference for nauplii. The study revealed the great importance of protozoa and bacteria in the trophic transfers between vegetal POM and zooplankton in the MTZ during summer, despite the low protozoa grazing pressure on vegetal POM (3.1%). The detritic food chain probably implies various trophic transfers with little direct relationships between vegetal POM and zooplankton.     

Distribution and residual activity of two insecticidal proteins, avidin and aprotinin, expressed in transgenic tobacco plants, in the bodies and frass of Spodoptera litura larvae following feeding

To understand how a major cosmopolitan pest responds to two very different insecticidal proteins and to determine whether herbivorous insects and their frass could be environmental sources of recombinant proteins from transgenic plants, Spodoptera litura (Fab.) (Lepidoptera, Noctuidae) larvae were fed on tobacco leaves expressing either the biotin-binding protein, avidin, or the protease inhibitor, aprotinin. Control larvae received non-transgenic tobacco. Samples of larvae were taken after 5, 6 or 7 days’ feeding and frass was collected after two 24-h periods at 6 and 7 days. Insects in all treatments grew significantly during the experiment, but the avidin-fed larvae were significantly smaller than the others on Day 7. Avidin was found in all samples of avidin-fed larvae (7.0±0.86 ng mg⁻¹, n=45), at a lower level than in their frass (31.9±5.08 ng mg⁻¹, n=30), and these frass levels were lower than those of the the leaves fed to the larvae (69.0±6.71 ng mg⁻¹, n=45). All of the avidin detected in these samples was capable of binding biotin. On average, between 10 and 28% of avidin was recovered with the methods used, whereas almost full recovery of aprotinin was effected. Aprotinin levels in larvae (8.2±0.53 ng mg⁻¹, n=45) were also lower than aprotinin levels in frass (77.4±6.9 ng mg⁻¹, n=30), which were somewhat lower than those in the leaves fed to the larvae (88.6±2.51 ng mg⁻¹, n=45). Approximately half the trypsin-binding ability of aprotinin was lost in larvae, and in frass, aprotinin had lost about 90% of its ability to bind trypsin.     

Synthesis, structure, and magnetic properties of dinuclear nickel(II) complexes with a phenol-based dinucleating ligand with four methoxyethyl chelating arms

Dinuclear nickel(II) complexes [Ni₂(bomp)(MeCO₂)₂]BPh₄ (1) and [Ni₂(bomp)(PhCO₂)₂]BPh₄ (2) were synthesized with the dinucleating ligand 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol [H(bomp)]. X-Ray analysis revealed that the complex 1 · 0.5CHCl₃ contains two nickel(II) ions bridged by phenolic oxygen and two acetate groups, forming a μ-phenoxo-bis(μ-acetato)dinickel(II) core. Electronic spectra were investigated for 1 and 2 in the range of 400-1800 nm, and the data were typical for the octahedral high-spin nickel(II) complexes. Obtained spectral components were well simulated based on the angular overlap model assuming the trigonally distorted octahedral geometry. Magnetic susceptibility was measured for 1 and 2 over a temperature range of 4.5-300 K. The optimized magnetic data were J = 1.75 cm⁻¹, zJ′ = −0.234 cm⁻¹, g = 2.21, D = 15.1 cm⁻¹, and TIP = 370 × 10⁻⁶ cm⁻¹ for complex 1 and J = 3.55 cm⁻¹, zJ′ = −0.238 cm⁻¹, g = 2.23, D = 21.8 cm⁻¹, and TIP = 470 × 10⁻⁶ cm⁻¹ for complex 2. The data revealed ferromagnetic interactions between the two nickel(II) ions.     

Cultivation of microalgae for oil production with a cultivation strategy of urea limitation

The microalgae, Chlorella sp., were cultivated in various culture modes to assess biomass and lipid productivity in this study. In the batch mode, the biomass concentrations and lipid content of Chlorella sp. cultivated in a medium containing 0.025–0.200 g L⁻¹ urea were 0.464–2.027 g L⁻¹ and 0.661–0.326 g g⁻¹, respectively. The maximum lipid productivity of 0.124 g d⁻¹ L⁻¹ occurred in a medium containing 0.100 g L⁻¹ urea. In the fed-batch cultivation, the highest lipid content was obtained by feeding 0.025 g L⁻¹ of urea during the stationary phase, but the lipid productivity was not significantly increased. However, a semi-continuous process was carried out by harvesting the culture and renewing urea at 0.025 g L⁻¹ each time when the cultivation achieved the early stationary phase. The maximum lipid productivity of 0.139 g d⁻¹ L⁻¹ in the semi-continuous culture was highest in comparison with those in the batch and fed-batch cultivations.     

Feeding and growth kinetics of the planktotrophic larvae of the spionid polychaete Polydora ciliata (Johnston)

We studied the effect of food concentration on the feeding and growth rates of different larval developmental stages of the spionid polychaete Polydora ciliata. We estimated larval feeding rates as a function of food abundance by incubation experiments with two different preys, presented separately, the cryptophyte Rhodomonas salina (ESD = 9.7 µm) and the diatom T.weissflogii (ESD = 12.9 µm). Additionally, we determined larval growth rates and gross growth efficiencies (GGE) as a function of R. salina concentration.P.ciliata larvae exhibited a type II functional response. Clearance rates decreased continuously with increasing food concentration, and ingestion rates increased up to a food saturation concentration above which ingestion remained fairly constant. The food concentration at which feeding became saturated varied depending on the food type, from ca. 2 µg C mL^− 1 when feeding on T. weissflogii to ca. 5 µg C mL^− 1 when feeding on R. salina. The maximum carbon specific ingestion rates were very similar for both prey types and decreased with increasing larval size/age, from 0.67 d^− 1 for early larvae to 0.45 d^− 1 for late stage larvae. Growth rates as a function of food concentration (R. salina) followed a saturation curve; the maximum specific growth rate decreased slightly during larval development from 0.22 to 0.17 d^− 1. Maximum growth rates were reached at food concentrations ranging from 2.5 to 1.4 µg C mL^− 1 depending on larval size. The GGE, estimated as the slope of the regression equations relating specific growth rates versus specific ingestion rates, were 0.29 and 0.16 for early and intermediate larvae, respectively. The GGE, calculated specifically for each food level, decreased as the food concentration increased, from 0.53 to 0.33 for early larvae and from 0.27 to 0.20 for intermediate larval stages.From an ecological perspective, we suggest that there is a trade-off between larval feeding/growth kinetics and larval dispersal. Natural selection may favor that some meroplanktonic larvae, such as P.ciliata, present low filtration efficiency and low growth rates despite inhabiting environments with high food availability. This larval performance allows a planktonic development sufficiently long to ensure efficient larval dispersion.