Net Growth Efficiency Research Articles

When less is more for dietary Lactobacillus rhamnosus IMC 501: The complex role gut microbiota play in energy budgets and allostasis of early juvenile Mozambique Tilapia (Oreochromis mossambicus)

In aquaculture, exposure to stressors results in heightened neuroendocrine responses, increasing metabolic activities and reducing growth to offset additional stressor-related energetic costs for allostasis. Supplementation with probiotics increases metabolic expenditures from elevated fish digestion and upregulated immune systems, but effects of the probiotics concentrations on energy budgets remains unknown. This study used respirometry to determine the effects of five different probiotic concentrations: T0 control (0 × 1011 CFU/g), T1 (5 × 1011 CFU/g), T2 (10 × 1011 CFU/g), T3 (15 × 1011 CFU/g), and T4 (20 × 1011 CFU/g) of a dietary single-strain probiotic (Lactobacillus rhamnosus IMC 501) on feed consumption, and the proportion of feed intake energy (C) allocated to growth (G), and routine metabolic rates (Rr), in the energy budgets of early juvenile (1-3 g wet weight) Mozambique tilapia (Oreochromis mossambicus), weekly over a 28-day experimental period. Two-factor ANOVA analyses revealed that the amount of feed intake energy (C) increased in probiotic treatments over controls. Allocation of feed energy for growth (G) differed among treatments, but not with time, but for routine metabolic activities (Rr), allocation of feed energy differed among treatments and over time. Increases of somatic tissue (TTW) was highest in the T2 treatment (intermediate concentration), while Rr was highest in the T3 and T4 (highest concentration) treatments, but only after 14–21 days of supplementation. Within energy budgets, the highest proportion of feed energy was allocated to growth in all treatments (G; mean ± SE, 43.0 ± 3.1 %), followed by routine metabolic activities (Rr; mean ± SE, 26.12 ± 2.1 %). Overall, the mean net mass-specific cost of growth (cr) (mgO2l−1 g−1) was highest, and the net growth efficiency (% KN) was lowest, in the T3 and T4 treatments indicating that higher probiotic concentrations were related to higher allostatic loads (AL) compared to lower probiotic treatments (T1, T2). Overall, our results revealed that the proportion of C allocated to G and Rr varied differently with probiotic concentration, was tightly related to gut bacteria metabolic expenditures, and highlighted the importance of carefully evaluating the probiotic concentrations for optimization of growth performance in Mozambique tilapia aquaculture.

Metabolic performance and feed efficiency of black soldier fly larvae.

The black soldier fly (BSF), Hermetia illucens, is used in entomoremediation processes because its larvae can use a variety of organic residues with high efficiency. However, feed efficiencies are variable and characterized by uncertainties. Recently developed growth and metabolic performance models have predicted across different studies that BSF larvae have used 53%-58% of the feed components they have assimilated, in terms of carbon equivalents, for growth throughout their lifetime when reared on chicken feed. This is termed their average net growth efficiency. The remainder of the carbon has been lost as CO2. However, mass balances made under similar conditions show that the weight gained by BSF larvae corresponds to only 14%-48% of the feed substrates removed, indicating substrate conversion efficiency. Both performance indicators show even greater variability if more feed substrates are considered. Feed assimilation and growth rates, costs of growth, maintenance, and larval lifespan have been shown to affect how efficiently BSF larvae convert feed into growth. The differences between average net growth efficiencies and substrate conversion efficiencies further indicate that feed is often not used optimally in entomoremediation processes and that the overall yield of such processes is not determined by larval performance alone but is the result of processes and interactions between larvae, substrates, microbes, and their physical environment. The purpose of this study is to illustrate how quantification of the metabolic performance of BSF larvae can help improve our understanding of the role of the larvae in entomoremediation processes.

Nimble vs. torpid responders to hydration pulse duration among soil microbes

Environmental parameters vary in time, and variability is inherent in soils, where microbial activity follows precipitation pulses. The expanded pulse-reserve paradigm (EPRP) contends that arid soil microorganisms have adaptively diversified in response to pulse regimes differing in frequency and duration. To test this, we incubate Chihuahuan Desert soil microbiomes under separate treatments in which 60 h of hydration was reached with pulses of different pulse duration (PD), punctuated by intervening periods of desiccation. Using 16S rRNA gene amplicon data, we measure treatment effects on microbiome net growth, growth efficiency, diversity, and species composition, tracking the fate of 370 phylotypes (23% of those detected). Consistent with predictions, microbial diversity is a direct, saturating function of PD. Increasingly larger shifts in community composition are detected with decreasing PD, as specialist phylotypes become more prominent. One in five phylotypes whose fate was tracked responds consistently to PD, some preferring short pulses (nimble responders; NIRs) and some longer pulses (torpid responders; TORs). For pulses shorter than a day, microbiome growth efficiency is an inverse function of PD, as predicted. We conclude that PD in pulsed soil environments constitutes a major driver of microbial community assembly and function, largely consistent with the EPRP predictions.

Differential quantities of zinc oxide nanoparticles incorporated feed on growth and haematological characteristics of Zebrafish (Danio rerio)

Zinc oxide nanoparticles were synthesized and characterized using by UV-Visible Spectroscopy (UV-Vis); Scanning Electron Microscope (SEM); Energy Dispersive X–Ray Spectroscopy (EDAX); X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Six feeds were prepared by using the differential quantities of Zinc oxide nanoparticles such as 0;20; 40; 60; 80 and 100 mg along with a fish meal; groundnut oil cake; wheat flour and tapioca flour. Feed utilization and haematological parameters of zebrafish were estimated after 21 days. The UV-visible absorption spectra demonstrate that Zinc oxide Nanoparticles were measured in wavelengths within 200 to 300 nm. SEM image shows that the Zinc oxide nanoparticles were observed at the wavelength range from 8.40 mm. EDAX spectrum recorded two peaks located between t 0.2KeV and 8.6 KeV. XRD image shows that the diffraction peaks of Zinc oxide nanoparticles are indexed as 041;142; 123; 281; 163; and 100;200. FT-IR spectrum was observed at the wavelength range from 3512 - 1500 cm-1. The condition factor of Zebrafish was decreased in the final when compared to the initial. The feed consumption and feed conversion efficiency of Zebrafish were higher in feed V. The feed conversion ratio of Zebrafish was best in feed III. Growth and the percentage growth of Zebrafish were higher in feed VI. Assimilation and metabolism of Zebrafish were higher in feed V. Gross and Net growth efficiency were higher in feed III. All the haematological parameters increased with increased quantities of zinc oxide nanoparticles.

Impact of differential quantity of iron oxide nanoparticles incorporated feed on growth, biochemical and haematological characteristics of Mrigal Cirrhinus mrigala

The present study deals with the impact of differential quantity of iron oxide nanoparticles incorporated feed on the growth, biochemical and haematological characteristics of Mrigal. Iron oxide nanoparticles were synthesised and characterized by using 5 UV-Vis spectroscopy(UV-Vis ) , Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDAX), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) andVibrating Sample Magnetometer (VSM). Six experimental feeds were prepared by using a fish meal, groundnut oil cake, wheat flour, tapioca flour and differential quantities of iron oxide nanoparticles such as 0, 10, 20, 30, 40, and 50 mg/100g. Feed utilization, biochemical and haematological characteristics of Mrigal were estimated after 21 days. UV-VIS Image spectra show that iron oxide nanoparticles were measured at a wavelength of “328 nm”. SEM image shows the morphological formation of iron oxide nanoparticles and was observed at the wavelength of 1μm.EDAX spectrum recorded on the iron oxide nanoparticles is shown as two peaks located between 0.2KeV and 6.4KeV. XRD results were obtained for the crystal nature of iron oxide nanoparticles and the average size is 20 nm. FT-IR spectrum of iron oxide nanoparticles was analyzed in the range from 4000-500 cm-1.VSM results revealed that saturation magnetization (MS) is 1.019 emu/gm present in iron oxide nanoparticles. The feed consumption, feed conversion efficiency, growth, and relative growth rate of Mrigal were higher in Ex. Feed III. The gross and net growth efficiency of Mrigal were higher in Ex. Feed I. All the blood parameters were gradually increased from Feed I to VI. The total protein, carbohydrate and lipids of Mrigal’s muscle, gill and liver of Mrigal is higher in Feed VI containing 50mg of iron oxide nanoparticles.

Seasonal energetic physiology in the ark shell Anadara kagoshimensis in response to rising temperature

Knowledge of physiological responses of important shellfish species to rising temperatures is crucial in assessing the impacts of climate change on marine aquaculture production. The physiological components of energy balance that support growth performance were measured seasonally at different exposure temperatures in the ark clams (Anadara kagoshimensis) cultured in the shallow muddy bottom sediment in Yeoja Bay, Korea. We tested the effects of winter minimum (3–8°C) and summer maximum (23–28°C) temperature elevations on individual physiological processes (ingestion, respiration, egestion, and excretion) and the combined energetic physiology (scope for growth [SFG] and net growth efficiency [K2] measures). The seasonal cycle of dry flesh tissue weight (DW) was also investigated from January 2016 to November 2018, to compare its variation at contrasting cold vs. warm regimes. The rates of physiological components were related to DW, generating significant allometric equations. The weight exponents of the equations for ingestion rate and respiration rate were low at the winter minimum compared with the remaining season temperatures, indicating a higher thermal sensitivity in larger individuals. The physiological rates that were re-calculated for individual components based on estimates of the slope and intercept of the equations increased with increasing temperature, revealing an incapability of thermal acclimation and a temperature effect at seasonally different endogenous conditions. The thermal sensitivity (Q10) of the ingestion rate and respiration rate was reversed between the winter minimum and the summer maximum temperature elevations, yielding negative SFG and K2 values at 3 and 28°C. Furthermore, the interannual difference in the seasonal cycle of clam DW displayed variations in the period of increment prior to spawning and the post-spawning loss/recovery in association with its energy balance status in the winter and summer temperature conditions. Overall, these results indicate that warming is projected to affect physiological performance and the seasonal DW cycle of clams in different manners between winter and summer: physiological benefits and advanced weight gain vs. heat stress and progressive weight loss, respectively. The mechanistic adjustment of the clam energy balance across thermal conditions seems to explain the recent advancement in its seasonal biological cycle, as well as the failure in spat collection and the mass summer mortality observed at this culturing site.

Impact of Different Quantity of Green Synthesized Iron Oxide Nanoparticles on Growth, Enzymatic, Biochemical Changes and Hematology of Zebrafish Danio rerio


 Nanoparticles such as Fe, FeO, CuO, Zn, ZnO, and Se play an important role in aquaculture. These compounds are essential minerals to increase fish growth and supplemen-tation in feeds because practical feedstuffs contain low levels of these microminerals. Dietary supplementation of nanoparticles produces greater survival, growth, antioxidant levels and immunity of aquatic organisms including fishes. The present study deals with the impact of different quantity of green synthesized iron oxide nanoparticles on growth, enzymatic, biochemical changes, and hematology of Zebrafish Danio rerio. Anisomeles malabarica leaf extract was used for the synthesis of iron oxide nano-particles and characterized by XRD, SEM, EDAX, and FT-IR. Six feeds were prepared with different quantity of synthesized iron oxide nanoparticles (F1 - Control, F2 -10 mg, F3 – 20mg, F4 – 30mg and F5 – 50mg) and feed ingredients are fish meal, groundnut oilcake, wheat flour, and tapioca flour. Growth, digestive enzymes (protease, amylase, and lipase), biochemical constituents (total protein, carbohydrate and lipid) and hematological parameters were estimated after 30 days. ‘t’ test and One-way ANOVA was used for the analysis. The feed consumption, feed conversion efficiency, weight gain, percentage growth, relative growth rate, assimilation, metabolism, gross and net growth efficiency were higher in F5 containing 40mg of green synthesized iron oxide nanoparticles (1.98 ± 0.29, 0.19 ± 0.02, 0.85 ± 0.32, 2.88 ± 0.74, 2.21 ± 0.70, 1.61 ± 0.11, 44.31 ± 10.58 and 42.11 ± 9.46). 40mg of iron oxide nanoparticles supplemented feed enhanced the digestive enzymes and biochemical constituents of Zebrafish. The results conclude that 40 mg iron oxide nanoparticles supplemented feed enhanced the growth, digestive enzymes, biochemical constituents, and hematology of Zebrafish.

A bioenergetic approach for a novel aquaculture species, the giant barnacle Austromegabalanus psittacus (Molina, 1788): Effects of microalgal diets on larval development and metabolism

Acorn barnacle aquaculture is a new activity based on species that possess potential due to several production advantages (e.g., no selective filters and rapid growth at very high densities). Extensive cultures have been developed in Chile and Portugal, but its settler (early juvenile) supply shows a high seasonal variability, which promotes the development of settler supplies from hatchery production. The effect of culture conditions on naupliar stages, cyprid and newly metamorphosed juvenile are key for hatchery production. Using the giant barnacle Austromegabalanus psittacus as model, we examined the effects of microalgae diets (Isochrysis galbana, Chaetoceros gracilis and a Mix 1:1 ratio) and concentration (2 × 105, 4 × 105 and 6 × 105 cells mL−1) on developmental time, mortality and metabolism (oxygen consumption, ammonia excretion and O:N ratio) from naupliar stages (NII-NVI) to cyprid stage. A bioenergetic approach was suggested to quantify how culture conditions influenced net growth efficiency for naupliar stages, as well as energy losses from cyprid and to newly metamorphosed juvenile. Nauplii fed with I. galbana did not fully complete naupliar stages, reaching a 100 % mortality at NIV stage. Overall, the shortest larval development time was observed at C. gracilis/2 × 105 cells mL−1 treatment along naupliar stages. The highest cyprid mortality was found in larvae fed during their development as nauplius with mixed diet at 2 × 105 cells mL−1. No differences in respiration and ammonia excretion rates between the treatments of each larval stage were found, with exception of cyprid from mix/2 × 105 cells mL−1. The highest dry weight of the cyprid and highest lipid content was obtained in C. gracilis/6 × 105 cells mL−1. The energy content provided by lipids and proteins for cyprid was significantly affected by diet and concentration. Outcomes from this study demonstrated that microalgae type and concentration have an important influence on larval development, survival and energy accumulation in A. psittacus.

Impact of substrate moisture content on growth and metabolic performance of black soldier fly larvae

Substrate moisture content is an important but not well-understood variable in production and waste reduction processes that involves black soldier fly (BSF) larvae. The purpose of this paper is to characterise growth and metabolic performance of BSF larvae on substrate moisture contents from 45 to 85%. Larvae developed into prepupae only at 45–75% substrate moisture content. Within this interval, the maximal specific growth rate was highest (0.73 day−1), the growth period shortest (13 days), and the maximal dry weight lowest (88 mg) at 45% moisture content. Differences in cost of growth and maintenance were not observed at the different substrate moisture contents, and differences in larval performance were likely associated to differences in co-occurring microbial activities. As much as 22% of the substrate carbon was emitted as CO2 at 45% moisture content by microorganisms, measured as the difference between total respiration and larval respiration, whereas microbial CO2 production amounted to only 3% of the substrate carbon at 75% moisture content. As consequence of the high specific growth rate and short growth phase, the overall net growth efficiency was higher at 45% moisture content (0.62) than at 75% moisture content (0.52). Overall, the metabolic performance of the BSF larvae was insensitive to differences in substrate moisture content. Their performance was, however indirectly affected by the substrate moisture content due to differences in co-occurring microbial processes in the substrate.

Evaluation of Different Quantity of Iron Oxide Nanoparticles on Growth, Haematological and Biochemical Characteristics of Koi Carp

Background: Nanoparticles such as Se, Cu, Fe, FeO, Zn and ZnO play a vital role in aquaculture operations and are essential microminerals to enhance fish growth. The dietary supplementation of nanoparticles produces better survival, growth, antioxidant levels and immunity in aquatic organisms. The present work aimed to evaluate the different quantity of Iron oxide nanoparticles on the Growth, Haematological and Biochemical Characteristics of Koi carp. Methods: Iron oxide nanoparticles were synthesized and characterized by using SEM, EDAX, FT-IR, XRD and VSM. Different quantity of iron oxide nanoparticles such as 0, 10,20,30,40 and 50mg/100g-1 was prepared along with the fish meal, groundnut oil cake, wheat flour and tapioca flour for feed I(Control), II, III, IV, V and VI respectively. Feed utilization, hematological and biochemical composition of Koi carp Cyprinus carpio var.koi were estimated after 21 days. Result: The feed consumption, feed conversion efficiency, feed conversion ratio, Growth and Specific Growth Rate, Gross and Net Growth Efficiency of Koi carp was higher in Ex. Feed IV. The Hematological parameters of Koi carp gradually increased from Feed I to VI. Total protein, carbohydrate and lipid in muscle, gill and liver of Koi carp were higher in Feed VI and lower in feed I. The present work suggests that growth parameters are better in feed IV and hematological and biochemical parameters are higher in feed VI.

Growth and metabolic performance of black soldier fly larvae grown on low and high-quality substrates

We have measured growth and respiration in black soldier fly (BSF) larvae fed with mixtures of a low-quality substrate (degassed sludge, DS), and a high-quality substrate (chicken feed, CF) in order to elucidate how substrate quality affect larval metabolism and feed conversion into new biomass. The BSF larvae grew faster and became larger the higher the content of CF was in the substrate. Growth followed a sigmoidal curve from where the specific growth rate was determined and compared to measured specific respiration rates, in order to estimate costs of growth, maintenance metabolism, rates of feed assimilation, and net growth efficiency. Specific feed assimilation rates were similar on all substrate mixtures. Maximal specific growth rates were also affected only little unless the larvae were grown in pure DS. In contrast, the cost of growth and the maintenance metabolism were larger the higher the proportion of DS was. High specific growth rates were, in addition, sustained for shorter periods of the time the more DS was included in the substrate mixtures. In effect, higher proportions of the assimilated feed were spent on respiratory purposes instead of being converted into larval biomass and the net growth efficiency decreased the more DS was included in the substrate mixtures. We conclude that substrate quality may affect the conversion of feed into new biomass via alterations of the metabolic performance of BSF larvae and thereby the overall performance of BSF larval cultures.

Scope for growth of cultivated Pacific and Gulf of California populations of lion's paw scallop Nodipecten subnodosus, and their reciprocal transplants

In the present work, the relative effects of the season (early vs. late summer), site (Gulf vs. Pacific study sites), the population of origin (Gulf vs. Pacific) and associated abiotic variables were determined in two geographically-separated Nodipecten subnodosus populations and their reciprocal transplants, through the scope for growth (SFG) and net growth efficiency (K2) using a portable open-flow system. Results indicate that both energy acquisition and expenditure were significantly affected by season, site, and population factors. Scallop energy acquisition and growth efficiency were highest during the earlier, cooler part of the summer and higher at the Pacific site where food availability was highest. Significantly higher respiration rates were measured for the Pacific scallop population, leading to significantly lower net growth efficiency than scallops of Gulf origin, which indicates a physiological advantage for Gulf scallops during the suboptimal growth conditions present during summer months on both coasts of the Baja California peninsula. It may have important implications for aquaculture enterprises in this region, and may also confirm the genetic divergence between these two geographically separated populations. The advantages of the open-flow system for in situ ecophysiological studies in aquatic organisms are discussed.

Seasonal variation in growth, consumption and growth efficiency in overwintering juvenile steelhead

AbstractFood availability and thermal regimes can largely govern growth opportunities in fishes. In temperate regions, streams can exhibit summer temperatures that exceed the optima for coolwater‐adapted species relative to the amount of available food, and therefore, spring and fall may confer better growing conditions, especially for larger size classes. We examined the relationship between growth, consumption and growth efficiency across seasons in juvenile steelhead (Oncorhynchus mykiss) in their natal streams in Idaho, USA. Subyearling (0+) growth rates were higher in summer, whereas yearlings exhibited no statistically significant difference in growth between seasons. Consumption rates were overall lower in winter–spring but constituted a higher proportion of maximum consumption compared with summer and fall, indicating better food availability relative to metabolic demands. Net growth efficiencies were higher in winter–spring, but substantially more so than the proportion of maximum consumption. This suggests that overwinter growth performance was driven at least partly by higher growth efficiency, and the effect was most pronounced for yearling steelhead. The low proportions of maximum consumption for both age classes suggest that food was an overall limiting factor to growth, especially in summer when metabolic demands were highest. We discuss how temperature‐based models can overestimate growth in the warmest parts of the year and develop a simple conceptual model for the seasonal timing of juvenile growth. In anadromous populations, the outmigration of presmolts in spring can reduce the level of competition. For the individuals that remain in the river, growth in this period can be particularly important.

Growth in pearl oysters: A review of genetic and environmental influences

Pearl oysters have high economic value. These species have gained much interest of research in growth, producing disease resistant and viable stocks for aquaculture facilities. Growth-related genes, such as insulin-related peptide receptor and the IGF system, and its components ERKs and MKK4 have been documented to influence growth in pearl oysters. Temperature, salinity, culture condition among other environmental factors were also reported to influence growth by influencing the physiological functions of pearl oysters such as clearance rate, oxygen consumption, respiration rate, excretion rate and expressed in parameters such as the scope of growth and the net growth efficiency. Genetic and artificial breeding techniques have been utilized in breeding programmes to improve growth and pearl quality in pearl oysters with mass selection and hybridization documented as efficient methods to improve growth traits. One problem observed during the growth of pearl oysters is the unsynchronized growth. Transcriptome and metabolomics studies have been undertaken to understand the underlying mechanism of this problem. The pearl oyster immune response to stress has also been reported to cause growth differences and needs to be thoroughly investigated to help produce viable stocks with synchronized growth for the aquaculture industry.

Effect of temperature, salinity, and body length on the energy budget of Daphniopsis tibetana Sars (Cladocera: Daphniidae)

We investigated the effects of temperature (14, 20, and 22°C), salinity (5, 10, 15, 20, and 25), and body length (0.83, 1.17, 1.49, and 2.33 mm) on the energy budget of Daphniopsis tibetana Sars in the laboratory. The results demonstrated no difference in D. tibetana assimilation efficiency (AE) with values of 51.59%–56.22% at the trial temperatures. Gross growth efficiency ( K1 ) and net growth efficiency ( K2 ) were 28.78% and 55.71%, respectively, at 14°C. Daphniopsis tibetana energy conversion efficiency (AE, K1, and K2) was higher at salinities of 10–20, with values of 72.80%–77.31%, 42.50%–50.42%, and 58.43%–65.02%, respectively. Daphniopsis tibetana energy conversion efficiency was highest when body length was 1.17–1.19 mm, with values of 83.70%–84.73%, 50.11%–50.81%, and 59.13%–60.71%, respectively. The results of this study can provide a reference for large-scale cultivation use of D. tibetana in the further.

More than morphology: Differences in food ration drive physiological plasticity in echinoid larvae

Previous studies examining echinoid larval development have observed food-dependent allometric growth in morphological features related to particle capture ability. The aim of the current study was to determine if in conjunction with this morphological plasticity, there was also evidence for physiological plasticity (i.e., food-dependent differences in mass-specific rates and/or energetic efficiencies). Larvae of the Pacific sand dollar, Dendraster excentricus, were fed relatively low and high amounts of algae (1,000 and 10,000algalcellsml−1, respectively). Morphological plasticity was observed, with low-fed larvae possessing longer ciliated bands and postoral arms relative to midline body length and stomach length. Rates of ingestion, metabolism, and growth (protein and lipid biomass) were measured throughout larval development to investigate differences in larval energy partitioning and growth efficiencies. Mass-specific rates of ingestion and respiration were ~2-fold higher in high-fed larvae, indicative of significant differences in physiological state. While total energy ingested reflected the 10-fold difference in feeding concentration, partitioning of energy between growth and metabolism was significantly different. Low-fed larvae possessed higher ingestion-related efficiencies (assimilation, gross growth, and protein growth efficiencies) that decreased with age. High-fed larvae exhibited consistently greater values of net growth efficiency throughout development. This increase was driven by increasing metabolic efficiency of protein deposition. A correlative analysis between rates of ingestion and metabolism demonstrated that both low- and high-fed larvae had a similar cost of feeding of 0.29 (±0.01; SE) μJ (algal cell ingested)−1. These results demonstrate that larval responses to food levels are not just morphologically plastic, but also physiologically plastic. It is important to further understand these mechanisms of physiological plasticity and their potential link to morphology. Such information will result in a more comprehensive understanding of larval growth and factors that influence recruitment success.

Light cycle effects on Haliotis discus hannai Ino growth, energy budget, and related gene expression

This study investigated the effects of different light cycles on growth, food intake, energy budget, and related gene expression of the abalone Haliotis discus hannai Ino. Abalones (mean±standard error shell length: 30.28±1.64mm, body weight: 4.51±0.49g) were exposed to the following light cycles: 0L:24D, 4L:20D, 8L:16D, 12L:12D, and 16L:8D for 60days, four repetitions were provided for each light cycle. At the end of the experiment, there was no significant difference in shell length or body weight growth rate between 0L:24D and 4L:20D (P>0.05), the values of which were significantly higher than in 16L:8D (P<0.05). In 0L:24D, abalone food intake was significantly higher compared with in the other groups (P<0.05), but the food conversion efficiency was significantly lower than in 4L:20D (P<0.05). At the end of the experiment, in 16L:8D, the activity of hexokinase was significantly higher than in any other group (P<0.05), but in 12L:12D and 16L:8D, it significantly increased compared with Day 30 (P<0.05). In 0L:24D, 4L:20D, and 8L:16D, cellulase and pyruvate kinase activity was significantly higher than in 12L:12D and 16L:8D (P<0.05). There was no significant difference in the energy acquired from food in 0L:24D and 4L:20D (P>0.05). However, the energy loss via feces and respiratory metabolism in 0L:24D was significantly higher than in 4L:20D (P<0.05); therefore, the energy accumulated for individual growth was significantly lower than in 4L:20D (P<0.05). Although the energy loss via feces, excretion, and respiratory metabolism was significantly lower in 16L:8D compared with 0L:24D, 4L:20D, and 8L:16D, the ratio of the energy loss via feces and respiratory metabolism to the energy acquired from food intake was significantly higher than in any other group (P<0.05); therefore, the net growth efficiency K2 was significantly lower (P<0.05). In 16L:8D, gene expression levels of manganese superoxide dismutase (Mn-SOD), catalase (CAT), TPx, heat shock protein (HSP) 26, HSP70, and HSP90 were significantly higher than in any other group (P<0.05). At the end of the experiment, Mn-SOD, CAT, and HSP70 expression in 16L:8D significantly increased compared with Day 30 (P<0.05). Therefore, considering aquaculture production and business costs, it would be appropriate to select the light cycle of 4L:20D for the culture of H. d. hannai.

Food selectivity and processing by the cold-water coral &amp;lt;i&amp;gt;Lophelia pertusa&amp;lt;/i&amp;gt;

Abstract. Cold-water corals form prominent reef ecosystems along ocean margins that depend on suspended resources produced in surface waters. In this study, we investigated food processing of 13C and 15N labelled bacteria and algae by the cold-water coral Lophelia pertusa. Coral respiration, tissue incorporation of C and N and metabolically derived C incorporation into the skeleton were traced following the additions of different food concentrations (100, 300, 1300 µg C L−1) and two ratios of suspended bacterial and algal biomass (1 : 1, 3 : 1). Respiration and tissue incorporation by L. pertusa increased markedly following exposure to higher food concentrations. The net growth efficiency of L. pertusa was low (0.08 ± 0.03), which is consistent with its slow growth rate. The contribution of algae and bacteria to total coral assimilation was proportional to the food mixture in the two lowest food concentrations, but algae were preferred over bacteria as a food source at the highest food concentration. Similarly, the stoichiometric uptake of C and N was coupled in the low and medium food treatment, but was uncoupled in the high food treatment and indicated a comparatively higher uptake or retention of bacterial carbon as compared to algal nitrogen. We argue that behavioural responses for these small-sized food particles, such as tentacle behaviour, mucus trapping and physiological processing, are more likely to explain the observed food selectivity as compared to physical–mechanical considerations. A comparison of the experimental food conditions to natural organic carbon concentrations above CWC reefs suggests that L. pertusa is well adapted to exploit temporal pulses of high organic matter concentrations in the bottom water caused by internal waves and downwelling events.

Nitrogen processing by grazers in a headwater stream: riparian connections

Summary Primary consumers play important roles in the cycling of nutrients in headwater streams, storing assimilated nutrients in growing tissue and recycling them through excretion. Although environmental conditions in most headwater streams and their surrounding terrestrial ecosystems vary considerably over the course of a year, relatively little is known about the effects of seasonality on consumer nutrient recycling these streams. In this study, we measured nitrogen accumulated through growth and excreted by the grazing snail Elimia clavaeformis (Pleuroceridae) over the course of 12 months in Walker Branch, identifying close connections between in‐stream nitrogen processing and seasonal changes in the surrounding forest. Nitrogen processing rates were positively correlated with ecosystem respiration, which was driven by leaf phenology on streamside trees. Snail nitrogen assimilation, growth and excretion were relatively high in spring before leaf emergence, low in summer when canopy shade was extensive and high again in autumn after leaf‐fall. During the time that snails grazed primarily on epilithon (winter, spring and summer), growth and excretion rates followed changes in light and epilithon biomass. In autumn, when snails primarily grazed fallen leaves, leaf‐associated microbes provided large subsidies of nitrogen for the snails. Nitrogen accumulation in snail biomass was greater in the 2 months following leaf‐fall than at any other time of the year. Snails were less important as nitrogen sinks than as sources of recycled nitrogen in Walker Branch. Over the course of the year, snails excreted approximately 12 times more nitrogen than they accumulated in biomass. Nitrogen accrued during growth in spring was subsequently lost in summer when primary production declined and snails underwent tissue loss. Catabolic losses represented &gt;40% of the nitrogen excreted by the snails in summer. Net nitrogen growth efficiency (growth/assimilation), which varied with food availability, was only 8% for the entire year. Neither growth nor excretion was positively correlated with nitrogen concentrations in grazing substrata. Snails achieved high standing crops and were significant contributors to nitrogen spiralling in Walker Branch. On an areal basis, nitrogen in snail biomass (mgN m−2) was two to five times greater than that in epilithon biomass, depending on the season. Snails assimilated and excreted up to 50% of the nitrogen initially taken up by autotrophs and leaf microbes, and they were likely to have additional effects on nitrogen spiraling through egestion and the cropping of assimilative biomass. Primary consumers like Elimia are important catalysts of nutrient movement through headwater streams, decreasing residence times and facilitating fluxes to downstream waters.

Timing is everything: optimizing crop yield for Thalassiosira pseudonana (Bacillariophyceae) with semi-continuous culture

There is relatively little choice in cultivation methods for growing algae outdoors, either in open pond systems or closed photobioreactors—as batch, continuous, or semi-continuous culture. Algal batch culture grown in a nutrient replete environment with adequate sunlight will become self-shaded with sufficient cell density and enter a stage in the growth dynamic known as the “phase of linear growth.” It is during this phase of linear growth that primary production is at maximum and that the highest biomass is harvested. The inherent problem with batch culture is that the exponential (and possibly lag) phases necessary to achieve densities required prior to the phase of linear growth consume time and waste surface area, and thereby make this an inefficient method to grow algae. Semi-continuous culture can be forced into shade-limiting conditions by reducing growth rate from maximum through dilution, whereby phases of lag and exponential growth are skipped, and culture growth is put into a state similar to a perpetual phase of linear growth with an appropriate culture harvest/dilution cycle. Importantly, semi-continuous culture can increase net growth efficiency over batch culture when compared by shade-limited growth rate. However, scientific study and theory covering shade-limited algal growth under semi-continuous culture conditions are nearly non-existent, which currently makes its application to phycological technologies impractical through “hit and miss” strategies. This laboratory study compares shade-limited growth dynamics for batch and semi-continuous cultures of Thalassiosira pseudonana (small-sized, marine diatom). Theory for optimizing production of mass algal culture with semi-continuous culture technique through cycle period and harvest volume is developed, and guidelines to practical industrial applications are provided.