Food Conversion Efficiency Research Articles

Partially purified Glycine max proteinase inhibitors: potential bioactive compounds against tobacco cutworm, Spodoptera litura (Fabricius, 1775) (Lepidoptera: Noctuidae)

Spodoptera litura (Fabricius, 1775), a polyphagous defoliator with broad host spectrum, causes significant damage to agriculturally important crops. Serine protease is primarily responsible for most of the proteolytic activity in the larval gut of lepidopteran insects. Second-instar larvae were reared on an artificial diet containing serine trypsin inhibitor partially purified from Glycine max seeds. Different concentrations were amended in the diet, i.e. 25, 50, 100, 200, and 400 μg/mL. The larval development period, total developmental period, longevity, fecundity, larval weight, and mean relative growth rate were decreased at the 100 μg/mL concentration. However, with further increase in concentration, the above parameters were all found to increase. Nutritional indices revealed reduction in efficiency of conversion of digested food and approximate digestibility, whereas increase in efficiency of conversion of ingested food had significant influence on food assimilation. Trypsin activity was suppressed at 100 μg/mL with increase in exposure interval. Results reveal that soybean protease inhibitor inhibited S. Litura gut proteinase and it was more effective at lower concentrations. Thus, low levels of inhibitor would be enough to affect the growth and development of the target pest for the development of transgenic plants.

Effects of various host plants on nutritional indices and some biochemical compounds in green oak leaf roller, Tortrix viridana L. (Lepidoptera: Tortricidae)

The green oak leaf roller, <em>Tortrix viridana</em> L., is one of the most destructive pests, causing damages to various species of oak, feeding on different host plants including <em>Quercus infectoria</em> Oliv, <em>Q. branti</em> Lindl, and <em>Q. libani</em> Oliv. Nutritional indices, activity of enzymatic and non-enzymatic compounds of <em>T. viridana</em> were studied under laboratory conditions. In addition, chemical components were analysed in the leaves of the three host plants. Fourth instar larvae reared on <em>Q. branti </em>showed the highest values of relative consumption rate (RCR), approximate digestibility, and consumption index (48.73±6.22; 90.45±1.06 and 97.45±12.44 respectively), while the lowest values were observed on <em>Q. libani</em>. Efficiency of conversion of ingested food in the fourth instar larvae was the highest (3.17±0.661) on <em>Q. libani</em> and the lowest (1.53±0.164) on <em>Q. branti</em>. The fifth instar larvae fed on <em>Q. libani</em> had the highest RCR (15.64±2.51). The highest amounts of triglycerides, uric acid, glucose, protein and the lowest activity of alkaline phosphatase were observed in the fifth instar larvae reared on <em>Q. libani</em>. The leaves of Q. libani highlighted the highest amounts of total nitrogen, total protein, water, potassium, magnesium and total carbohydrate. The present research suggested that the nutritional quality of the host plants have crucial effects on <em>T. viridana</em> larvae.

Feeding ecology of mackerel and dietary overlap with herring in Icelandic waters

ABSTRACTThe Northeast Atlantic mackerel (Scomber scombrus) has been extending its summer feeding distribution north and west, including around Iceland, since around 2006. The objective of this study is to quantify the weight gain and total food consumption of mackerel and to evaluate the food competition between mackerel and herring (Clupea harengus) feeding in the marine ecosystem around Iceland during the summers 2009–2011. Mackerel feeding in Icelandic waters gained around 43% on average in weight during these summers. Based on swept-area abundance estimates of mackerel from an international survey in 2011 and available estimates of food conversion efficiency in mackerel, the weight gain in Icelandic waters in 2011 corresponded to a total consumption of around 3.4 (2.4−4.5) million tonnes. Overall, 98% of 2314 mackerel, 91% of 398 Icelandic summer-spawning herring and 96% of 424 Norwegian spring-spawning herring stomachs, collected over the summers 2009−2011, contained food. The mean weight of the stomach content of mackerel was higher than for herring in all the years. While the stomach content weight of mackerel was generally highest in southeastern and southwestern areas, it was highest for herring in western, eastern and northern areas. Analysis of stomach contents showed that Copepoda were the most important food of mackerel in most areas, while Copepoda and Euphausiacea were the most important food items for herring. Fish prey contributed a higher proportion in stomachs of mackerel than herring, although relatively low for both species.

Effects of LED light quality on the growth, metabolism, and energy budgets of Haliotis discus discus

In this study, a bioenergetics approach was used to examine the effects of different LED light qualities (red, orange, blue, green light, natural light and a dark setting) on the growth and survival of the abalone Haliotis discus discus, and its physiological response mechanism under different light qualities. The results suggest that under blue or green light, the survival rate, specific growth rate, food intake, and food conversion efficiency of H. d. discus were significantly lower than in those groups under red or orange light (P<0.05). Under red or orange light, pepsin, amylase and cellulose activity was significantly higher than those in any other light quality group (P<0.05), whereas lipase activity exhibited no significant difference among the light quality groups (P>0.05). Under blue or green light, lactate dehydrogenase activity and lactic acid content were higher (P<0.05), suggesting enhanced anaerobic metabolism. Under blue or green light, H. d. discus lost more energy via excretion, feces and respiration than was acquired from its food. Under red or orange light, H. d. discus acquired more energy from its food and lost less energy via excretion and feces; as a result, its assimilation efficiency (K1) and net growth efficiency (K2) were significantly higher than those of any other group (P<0.05). Therefore, we suggest that red or orange light should be used as a light source for the aquaculture of H. d. discus.

Biogenic acidification reduces sea urchin gonad growth and increases susceptibility of aquaculture to ocean acidification

Decreasing oceanic pH (ocean acidification) has emphasised the influence of carbonate chemistry on growth of calcifying marine organisms. However, calcifiers can also change carbonate chemistry of surrounding seawater through respiration and calcification, a potential limitation for aquaculture. This study examined how seawater exchange rate and stocking density of the sea urchin Tripneustes gratilla that were reproductively mature affected carbonate system parameters of their culture water, which in turn influenced growth, gonad production and gonad condition. Growth, relative spine length, gonad production and consumption rates were reduced by up to 67% by increased density (9–43 individuals.m−2) and reduced exchange rates (3.0–0.3 exchanges.hr−1), but survival and food conversion efficiency were unaffected. Analysis of the influence of seawater parameters indicated that reduced pH and calcite saturation state (ΩCa) were the primary factors limiting gonad production and growth. Uptake of bicarbonate and release of respiratory CO2 by T. gratilla changed the carbonate chemistry of surrounding water. Importantly total alkalinity (AT) was reduced, likely due to calcification by the urchins. Low AT limits the capacity of culture water to buffer against acidification. Direct management to counter biogenic acidification will be required to maintain productivity and reproductive output of marine calcifiers, especially as the ocean carbonate system is altered by climate driven ocean acidification.

Efficacy of sub lethal concentration of entomopathogenic fungi on the feeding and reproduction of Spodoptera litura.

In the present investigation, impact of sub lethal concentrations of entomopathogenic fungi, namely Isaria fumosorosea, Beauveria bassiana and Paecilomyces variotii, secondary metabolite on feeding, growth, fecundity and hatchability of Spodoptera litura was performed. The S. litura treated with I. fumosorosea and B. bassiana metabolites exhibited renounced food consumption. The growth rate of treated S. litura with metabolite of I. fumosorosea had drastic reduction. In the case of approximate digestibility (AD), maximum impact was established by the I. fumosorosea isolate, which significantly reduced the approximate digestibility of the IV and V instar larvae. The III instar larvae of S. litura treated with I. fumosorosea metabolite showed significantly lower efficiency of conversion of digested food (ECD) and efficiency of conversion of ingested food (ECI) values than IV and V instars. However the performance of metabolites on fecundity and hatchability of S. litura was immense. Therefore, metabolites of I. fumosorosea could be reliable biocontrol agent, which has been highly recommended for S. litura management in commercial crops.

English

In the study reported herein, we aimed to isolate a trypsin inhibitor from Ricinus communis leaves through chromatographic and spectrometric techniques and evaluate its toxic effects on the development of Spodoptera frugiperda larvae. Plant extracts were submitted to fractionation in adsorption column. The fraction 10, which showed the highest inhibitory activity, were incorporated into an artificial diet at the concentrations of 0, 0.06, 0.12, 0.25 and 0.5%, and offered to S. frugiperda larvae. Fresh weight of larvae, food consumed and weight of eliminated faeces were registered. Based on these parameters the following nutritional index were calculated: Relative Consumption Rate (RCR), Relative Metabolic Rate (RMR), Relative Growth Rate (RGR), Approximated Digestibility (AD), Efficiency of Ingested Food Conversion &nbsp;(EIC), Efficiency of Digested Food Conversion (EDC) and the Metabolic Cost (100 - EDC). The inhibitor at 0.5% concentration was deleterious to S. frugiperda, extending the larval stage in 11 days, with higher RCR and ECD, and lower RGR, ECI and ECD. Therefore, the trypsin inhibitor from leaves of R. communis affected the S. frugiperda larval development, being promising in studies of alternative and sustainable control methods for lepidopteran pest species. &nbsp; Key words: Castor beans, enzymatic inhibition, integrated pest management, plant defense against herbivory. &nbsp

Residual toxicity of bait formulations containing plant essential oils and commercial insecticides against the desert locust, Schestocerca gregaria (Forskäl)

Essential oils extracted from seven different plants belonging to five families, and four commercial insecticides representing different chemical classes were tested against the 3rd nymphal instars of the desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae) by bait application technique. The bait was prepared from wheat bran with molasses and fortified with different amounts of the studied toxicants, then introduced to the insect in cages. Methomyl, the most potent insecticide showed LC50 of 0.051μg/g. Fenvalerate, Fenitrothion, and Carbosulfan possessed potency accounted to 49.0%, 34.2%, and 9.0%, respectively, compared with Methomyl potency (100.0%). Cumin (Cuminum cyminum) oil was the highest toxic to the nymphs, while Parsley (Petroselinum sativum) was the lowest. Out of the eleven screened substances, 3 insecticides and 3 plant oils were subjected to detailed residual toxicity investigations at their corresponding LC90 values. The criteria of assessment included estimation of T50 and T20 values (time in days at which mortality declined to 50% and 20%, respectively), feeding activity, reproductive potential, and histopathological alterations in the rectal pads of the tested insect. For example, the T50 and T20 values for Methomyl equalled to 2.0 and 7.3 days, compared with 3.0 and 5.9 days, respectively, for Onion (Allium cepa) oil. Generally, Fenvalerate and Fenitrothion possessed T20 values higher than those obtained for Sweet Basil (Ocimum basilicum) and Cumin. Compared to control, Sweet Basil oil decreased severly consumption index (C.I.), efficiency of conversion of digested (E.C.D.) and ingested (E.C.I.) food. The growth rate was significanly declined by Fenitrothion, Fenvalerate, Sweet Basil, and Onion. Fenitrothion, Cumin, and Onion decreased approximate digestibility. The tested toxicants affected oviposition periods, number of egg pods and eggs laid per female and the total number of hatched eggs. The latter were found 305 eggs in control treatment, compared with 20, 74, 107, 120, 150, 117 eggs for Fenitrothion, Methomyl, Fenvalerate, Onion, Sweet Basil, and Cumin treatments, respectively. Except Cumin treatment, the other treatments caused anatomical alterations in the rectum of the adult S. gregaria represented by increasing length and width of rectal pads, as well as increase of epithelial cells. We may claim that the over all results of this study may be considered as novel findings in the course of searching for potent biopesticides against the locust, S. gregaria, and encourage further research under field conditions.

Toxicity of Alangium salvifolium Wang chemical constituents against the tobacco cutworm Spodoptera litura Fab

Widespread use of synthetic pesticides has resulted in the development of insecticide-resistant populations of pests and harmful effects on human health and the environment. There is a need to identify alternative pest management strategies to reduce our reliance on conventional chemical pesticides. In recent years the use of botanical pesticides for protecting crops from insect pests has assumed greater importance. Methanol extract of Alangium salvifolium (L.f.) Wang has potential insecticidal activity against Spodoptera litura Fab. The active fractions were identified through chromatographic techniques as F-IV (Rf value=0.45) and F-VI (Rf value=0.63) and were subjected to GC–MS (GCMATE II). Fifty, 100 and 200ppm of active fractions were applied to fourth instar larvae and the mortality increased with higher concentrations. Relative consumption rate, relative growth rate, efficiency of conversion of ingested food and efficiency of conversion of digested food values all decreased in treated larvae, but approximate digestibility rate increased after treatment. The hydrolytic enzymes, such as acid phosphatase, alkaline phosphatase and the glycolytic enzyme lactate dehydrogenase were inhibited in treated larvae compared with controls. The histopathology study revealed that the epithelial columnar cells were enlarged, completely atrophied; intercellular spaces were swollen, and also noted a cytoplasmic ooze of cell material that mixed with food column. The present study clearly showed the active fractions from A. salvifolium as potential botanicals to control the larvae of S. litura. This is the first report for nutritional indices, enzymatic activities and histological effects of A. salvifolium chemical constituents against S. litura. Thus probably, this will be used as an alternative for synthetic pesticides against the polyphagous pest like S. litura.

Effects of dietary protein levels on the growth, energy budget, and physiological and immunological performance of green, white and purple color morphs of sea cucumber, Apostichopus japonicus

Protein is a necessary nutrient for the sea cucumber, Apostichopus japonicus, an important commercial species in China, South Korea and Japan. In this study, the dietary protein requirements of two newly discovered color morphs—white and purple was investigated and compared with the common, green morph. The green, white and purple morphs were fed a diet with five different protein levels (1, 6, 11, 16 and 21%) for 60days with a mixture of soybean meal and fish meal (1:1) as the protein source, and their growth, energy budget, physiological and immunological performance were measured. Results showed that dietary protein levels had a significant effect on the growth performance of A. japonicus (P<0.05). The maximum specific growth rate (SGR) and proportion of energy allocated for growth occurred at dietary protein levels of 6 and 11%, and the food conversion efficiency (FCE) was highest at the 11% protein level, indicating that the optimum dietary protein level for these color morphs is at ~11%. Apparent digestibility coefficients for dry matter (ADMD) and crude protein (ACPD) increased, but the ingestion rate decreased with increasing dietary protein levels, due perhaps to the decreased sea-mud content of the diets. The energy allocated to excretion, and the free ammonia and malonaldehyde content in coelomic fluid increased with increasing dietary protein levels, which can be explained by enhanced protein metabolism. Trypsin activity decreased significantly when dietary protein was >16%, indicating that the protein content was beyond the digestive ability of sea cucumber, and that excess protein in the diet inhibits protein digestion. Catalase (CAT) and glutamic–oxaloacetic transaminase activity was positively and significantly correlated with SGR, indicating that rapid growth was supported by a robust immune system and effective protein metabolism. At a 1% dietary protein level, the purple color morph had significantly higher SGR, FCE, ACPD and CAT activity, and allocated more energy for growth than the green morph, indicating that the purple morph may be better adapted to a low protein diet than the green morph. The white morph had lower SGR, FCE, superoxide dismutase (SOD) and CAT activity, and allocated less energy to growth, but had a higher excretion energy and higher free ammonia content in coelomic fluid than the green or purple morphs, indicating a difference or physiological defect in protein metabolism in the white morph. Statement of relevanceThe results of this study would be invaluable in improving aquaculture technology and management strategies for green, white, and purple color morphs of Apostichopus japonicus.

Insecticidal and antifungal potentials of a proteinaceous extract of Cassia occidentalis (Linn.) seeds

Proteinaceous extract obtained from Cassia occidentalis seeds with purification fold of 3.91 and 82.7% of bovine trypsin inhibitory activity was assessed at different concentrations (25, 50, 100, 200, 400 and 800 μg/ml) against Spodoptera litura. Assay of larval feeding suggested proteinaceous extract to be toxic as prepupal (80.16%) and pupal mortalities (100%) along with growth deterrent effect with only 16.71% pupation was observed at 800 μg/ml. Fifty per cent mortality (LC50) was observed at 132.91 μg/ml. Also the inhibitor affected fecundity, longevity and percentage of egg hatching. Nutritional indices were adversely affected as both efficiency of conversion of ingested and digested food decreased while approximate digestibility and metabolic cost increased. In vitro studies on proteolytic enzymes of S. litura revealed inhibition of trypsin and chymotrypsin in lumen and faecal matter at all tested concentrations. Also proteinaceous extract inhibited mycelial growth in Fusarium oxysporum, Alternaria brassicicola and Alternaria alternata at 100 μg/ml.

Effect of Larval Density on Food Utilization Efficiency of Tenebrio molitor (Coleoptera: Tenebrionidae).

Crowding conditions of larvae may have a significant impact on commercial production efficiency of some insects, such as Tenebrio molitor L. (Coleoptera: Tenebrionidae). Although larval densities are known to affect developmental time and growth in T. molitor, no reports were found on the effects of crowding on food utilization. The effect of larval density on food utilization efficiency of T. molitor larvae was studied by measuring efficiency of ingested food conversion (ECI), efficiency of digested food conversion (EDC), and mg of larval weight gain per gram of food consumed (LWGpFC) at increasing larval densities (12, 24, 36, 48, 50, 62, 74, and 96 larvae per dm(2)) over four consecutive 3-wk periods. Individual larval weight gain and food consumption were negatively impacted by larval density. Similarly, ECI, ECD, and LWGpFC were negatively impacted by larval density. Larval ageing, measured as four consecutive 3-wk periods, significantly and independently impacted ECI, ECD, and LWGpFC in a negative way. General linear model analysis showed that age had a higher impact than density on food utilization parameters of T. molitor larvae. Larval growth was determined to be responsible for the age effects, as measurements of larval mass density (in grams of larvae per dm(2)) had a significant impact on food utilization parameters across ages and density treatments (in number of larvae per dm(2)). The importance of mass versus numbers per unit of area as measurements of larval density and the implications of negative effects of density on food utilization for insect biomass production are discussed.

ENGARUH PEMBERIAN KULIT KOPI TERFERMENTASI DAN LEGUMINOSA UNTUK PERTUMBUHAN KAMBING PERANAKAN ETAWAH

&lt;div data-canvas-width="788.5183333333333"&gt;Waste coffee planthas the potential to be used as abooster feed for livestock. Coffee fruit waste composition physically&lt;/div&gt;&lt;div data-canvas-width="802.6816666666667"&gt;quite largeat around 48% on coffee pulp. Research was conducted to examine the effect on the growth of Etawah Crossbred&lt;/div&gt;&lt;div data-canvas-width="802.7"&gt;Goat (PE) after the treatment of fermented coffee waste as the substitution for leguminous (gamal and kaliandra). Twelve&lt;/div&gt;&lt;div data-canvas-width="802.6816666666665"&gt;5-6 months old male PE goats were involved with 20 kg early weight average. Three groups of feeding treatment were&lt;/div&gt;&lt;div data-canvas-width="802.6883333333332"&gt;considered: Treatment P1 = 100% leguminous (gamal and kaliandra in ratio 1:1); Treatment P2 = 70% leguminous&lt;/div&gt;&lt;div data-canvas-width="802.7016666666666"&gt;(gamal and kaliandra in ratio 1:1) + 30% fermented coffee Pulp; Treatment P3 = 40% leguminous (gamal and kaliandra&lt;/div&gt;&lt;div data-canvas-width="802.7049999999998"&gt;in ratio 1:1) + 60% fermented coffee Pulp. Result of research indicated that the average increase of daily body weight&lt;/div&gt;&lt;div data-canvas-width="802.6700000000003"&gt;of PE goat in the Treatment P1 (88.93 grams/goat/day) and P2 (100.00 grams/goat/day) was not obviously different (P&lt;/div&gt;&lt;div data-canvas-width="802.65"&gt;&amp;gt; 0.05), but both were obviously different (P &amp;lt; 0.05) from P3 (71.79 grams/goat/day). Treatment P3 showed the lowest&lt;/div&gt;&lt;div data-canvas-width="802.6433333333331"&gt;level of the consumption of DM, OM and the lowest level of gross energy, and had obvious difference (P &amp;lt; 0.05) from&lt;/div&gt;&lt;div data-canvas-width="802.6483333333332"&gt;P1 and P2. Meanwhile, P1 and P2 were not obviously different (P &amp;gt; 0.05). From these results, it was concluded that the&lt;/div&gt;&lt;div data-canvas-width="802.6799999999998"&gt;treatment of fermented coffee Pulp by 30 % and of leguminous (gamal and kaliandra) by 70 % (at P2) were giving the&lt;/div&gt;&lt;div data-canvas-width="573.0833333333331"&gt;best growth for PE goat. Indeed, P2 also displayed the most efficient food conversion.&lt;/div&gt;

Biogenic acidification drives density-dependent growth of a calcifying invertebrate in culture

A major factor often overlooked in the production of calcifying marine invertebrates in aquaculture is the effect of changes in the carbonate chemistry of culture water caused by organism metabolism and calcification. This study examined the effects of temperature, stocking density and seawater exchange rate on the survival and growth of the juvenile sea urchin, Tripneustes gratilla with particular reference to effects of these factors on the carbonate chemistry of culture water. Growth and survival of T. gratilla were highest at 26–28 °C. Growth rates, relative spine length, consumption rates and food conversion efficiency were reduced by up to 50 % by an increase in stocking density from 43 to 129 individuals m−2 and a reduction in seawater exchange rate from 3.0 to 0.3 exchanges h−1, but survival rates were unaffected. Analysis of the influence of seawater parameters indicated that total alkalinity (AT), calcite saturation state (ΩCa) and dissolved CO2 were the primary factors limiting growth at high densities and low seawater exchange rates. Uptake of bicarbonates for calcification and release of respiratory CO2 by T. gratilla appeared to be driving changes in carbonate chemistry. Our results show that reduced capacity of culture water to buffer acidification (low AT) can be a limiting factor in intensive production of calcifying marine invertebrates. This study demonstrates the importance of considering the influence of biogenic CO2 on seawater carbonate chemistry in aquaculture, particularly given the threat of reduced pH of source water due to ocean acidification, and also in experiments investigating the influence of anthropogenic CO2.

Comparative study to determine food consumption of cotton leafworm, Spodoptera littoralis, on some cotton genotypes

AbstractA study was done on the feeding behaviour, development indices, and biochemical response of 4th instar larvae ofSpodoptera littoralisin which seven cotton genotypes were used: Giza86, Giza88, Giza92, 10229 × Giza 86, H10, Suvin, and Karshenseki. Castor bean leaves were used as the control. All the tested cotton genotypes decreased the feeding behavior ofS. littoralislarvae in terms of consumption percentages, consumption rate (CR), growth rates (GR), efficiency of conversion of ingested and digested food (ECI and ECD), approximate digestibility (AD), and feeding deterrence (FDI) compared to the control. Additionally, all the tested cotton varieties prolonged the time taken for larval and pupal duration and reduced both the pupation percentages and the weight of the resulting pupae, as compared to the control. Giza86 recorded the lowest values of both larval growth index and fitness (7.31 and 1.05, respectively) while the genotype Suvin recorded the lowest standardised growth index (0.020) more than other genotypes and the control that gave 10.16, 1.53, and 0.032, respectively. There was a significant inhibition in the level of both total soluble protein and total lipids, and activities of amylase and the trehalase enzymes in all the tested varieties, compared to that found in the control.

Effect of Beauveria bassiana infection on the feeding performance and antioxidant defence of red palm weevil, Rhynchophorus ferrugineus

The entomopathogenic fungal infection of target hosts depends on pathogen fitness and host defence mechanisms. Pathogen-host interactions in red palm weevil, Rhynchophorus ferrugineus larvae are poorly understood. In order to explore this interaction, 4th, 8th, and 12th instar red palm weevil larvae were immersed in conidial suspensions of four isolates of Beauveria bassiana. Significant differences in the virulence of the tested isolates were revealed by LT50 values. Conidia of B8463, a highly virulent isolate, showed 33.53 % higher relative hydrophobicity and twice as much Pr1 activity than conidia of B8465. Growth indices, calculated after 72 h of incubation, revealed significant differences in the food utilization efficiencies of all studied larval instars infected with different isolates. Conidial infection with B8463 caused 39–45 % reduction in efficacy of consumption of ingested food (ECI) and 55–61 % reduction in digested food (ECD). The least virulent isolate, B8465, caused the smallest reduction in ECI (2–4 %) and ECD (3–9 %). Furthermore, enhanced expression of target antioxidant genes (catalases and peroxidase) was observed in larvae infected with virulent isolates. Similarly, approximate digestibility showed an opposite trend, with the highest values being recorded from samples infected with the most virulent conidia (B8463) at each studied larval instar. In conclusion, isolate B8463 significantly affected the growth and development of red palm weevil larvae and has good potential for use in eco-friendly R. ferrugineus management.

Growth and immune system performance to assess the effect of dispersed oil on juvenile sea bass (Dicentrarchus labrax)

The potential impact of chemically and mechanically dispersed oil was assessed in a model fish of European coastal waters, the sea bass Dicentrarchus labrax. Juvenile sea bass were exposed for 48h to dispersed oil (mechanically and chemically) or dispersants alone. The impact of these exposure conditions was assessed using growth and immunity. The increase observed in polycyclic aromatic hydrocarbon metabolites in bile indicated oil contamination in the fish exposed to chemical and mechanical dispersion of oil without any significant difference between these two groups. After 28 days of exposure, no significant differences were observed in specific growth rate,apparent food conversion efficiency and daily feeding). Following the oil exposure, fish immunity was assessed by a challenge with Viral Nervous Necrosis Virus (VNNV). Fish mortality was observed over a 42 day period. After 12 days post-infection, cumulative mortality was significantly different between the control group (16% p≤0.05) and the group exposed to chemical dispersion of oil (30% p≤0.05). However, at the end of the experiment, no significant difference was recorded in cumulative mortality or in VNNV antibodies secreted in fish in responses to the treatments. These data suggested that in our experimental condition, following the oil exposure, sea bass growth was not affected whereas an impact on immunity was observed during the first days. However, this effect on the immune system did not persist over time.

Calculation of the physiochemical parameters of catfish (Clarias gariepinus) fed locally formulated feeds (earth worm)

This study was conducted in the biological department of the University of Abuja; to access the physiochemical parameters of catfish (Clarias gariepinus) fed locally earth worm fishmeal. The earth worm meal is composed of fishmeal (400g), corn (280g), rice bran (200g), and groundnut cake (120g). Proximate Analysis was analyzed as follows: Moisture (60g), Crude protein (12), Ash (10), and Crude lipid (12). The earthworm meal varies with replacement level at 0%, 30%, and 50% for Treatment A, B, and C respectively. Fishes were stocked at a density of 15 fingerlings per tank and fed twice daily at 4% body weight. From result obtained, temperature in all the treatments were within the same range (26 o C-27 o C), dissolved oxygen concentration for treatment A (4.98mg/l) was below the optimum level for good growth,(5.03mg/l), and pH level shows alkalinity in all the treatment ranging from 7.10 - 8.71, and nitrate level (0.01-0.04mg/l) was observed to be optimal in all treatments. Concentration of ammonia ranged from (0.01-8mg/l) in Treatment A, B, and C. Highest value of mean weight (0.33g) and mean length (0.34cm) gained was noticed in Treatment C. The result shows a significant differences (P<0.05) on the mean weight, mean length, specific growth rate, food conversion efficiency and survival rate. Earthworm meal is therefore considered effective, on the basis of good water quality to enhance production and survival performance.

First Attempt of Complete Rearing of Tea Looper, Biston (=Buzura) suppressaria, on Artificial and Natural Diet

Complete rearing of the looper pest, Biston (=Buzura) suppressaria (Guen.) (Lepidoptera: Geometridae) through generations has been attempted for the first time on artificial diet as an alternative to tea-leaf diet. A comparative study on performance of the pest on its natural host, tea (Camellia sinensis, O’Kuntz), and on the newly formulated artificial diet revealed adequacy and superiority of the latter diet. The development period of B. suppressaria was shorter (48 days) on artificial diet, with a better survival rate than that on tea. On artificial diet the species showed a greater effective rearing rate with production of heavier pupae and adults. Nutritional indices determined for advanced looper stage tilted in favour of artificial diet as compared to that on tea with significantly higher relative growth rate, efficiency of conversion of ingested food, efficiency of conversion of digested food, approximate digestibility, production index and significantly lower maintenance cost.

Species‐specific effects of subdaily temperature fluctuations on consumption, growth and stress responses in two physiologically similar fish species

AbstractFluctuations in water temperature can have important physiological consequences for fishes. Effects of daily thermal cycles are well studied and can be beneficial, increasing prey consumption and growth rates when mean and maximum temperatures of the fluctuations are at or below the species’ optimum temperature. While less studied, subdaily temperature fluctuations are also common in many aquatic habitats and can be caused by both natural and anthropogenic processes. We performed laboratory experiments to examine how two fish species (yellow perch, Perca flavescens, and walleye, Sander vitreus) with similar thermal preferences respond to chronic exposure to subdaily temperature variability. We selected temperature treatments that reflected observed thermal variation after examining water temperature data from multiple aquatic systems. We then separately exposed yellow perch and walleye to a stable 23 °C treatment and 12‐h cycles of 23 ± 2 °C or 23 ± 4 °C for 45 days. Adult yellow perch exposed to fluctuations of 23 ± 4 °C over 12 h expressed higher consumption, growth and food conversion efficiency than fish experiencing stable 23 °C. Temperature fluctuations, though, resulted in mortalities and the development of skin ulcers in yellow perch that did not occur under stable temperatures. In contrast, the same 12‐h temperature fluctuations did not result in mortalities or stress responses in juvenile walleye. Moreover, unlike yellow perch, growth rates of walleye were lower under 12‐h temperature fluctuations compared with the stable 23 °C treatment. Our results indicate that species with similar thermal preferences can respond differently to the same subdaily temperature fluctuations.