Insecticidal activity influence of destruxins on the pathogenicity of Paecilomyces javanicus against Spodoptera litura

Abstract:  The bioactivities of destruxins (dtx), depsipeptides isolated from Metarhizium anisopliae , against Spodoptera litura were tested in laboratory. For contacting toxicities, dtx-E was more effective than dtx-A and dtx-B. The LC₅₀s values of dtx-A, B and E were 197.98, 292.00 and 113.99 mg/l at 48 h after treatment, while the LT₅₀s were 42.65, 59.45 and 23.68 h at 300 mg/l. In the experiment of antifeedant activity, dtx-A, dtx-B and dtx-E at five concentrations (200, 100, 50, 25 and 12.5 mg/l) were bioassayed. Destruxins in a dose-dependent manner gave an apparent antifeedant activity. Generally, dtx-A, over dtx-B and dtx-E had the significant (P < 0.05) larger choice and no-choice antifeedant indexes (CAIs and NCAIs). At the concentration of 200 mg/l, the CAIs or NCAIs of dtx-A, dtx-B and dtx-E were 96.78, 84.93 and 85.90 or 89.75, 62.42 and 72.28 respectively. Furthermore, the synergistic activity of crude destruxin (CD) for pathogenicity of Paecilomyces javanicus strain Pj01 was detected. The LC₅₀s values of single Pj01 and the mixtures of Pj01 plus CD at 100 or 200 mg/l (Pj01-CD100 or Pj01-CD200) were respectively 474.63 × 10⁵, and 197.45 × 10⁵ or 113.11 × 10⁵ spores/ml at the fifth day after treated. Meanwhile, Pj01, Pj01-CD100 and Pj01-CD200 gave the LT₅₀s values of 6.99 day, 5.49 day and 4.21 day at 100 × 10⁵ spores/ml. Clearly, dtx decreased the values of LC₅₀ and LT₅₀ of the strain Pj01.     

Relative toxicity of nC24 agricultural mineral oil to Tetranychus urticae Koch (Acari: Tetranychidae) and Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) and its possible relationship to egg ultrastructure

The relative toxicity (LC₅₀ values based on µg oil/cm²) is evaluated of aqueous n C24 agricultural mineral oil (AMO) emulsions to the egg, six-legged nymph (larva), eight-legged protonymph and adult stages of two-spotted mite ( Tetranychus urticae ) and its predator, Phytoseiulus persimilis , on French bean leaf discs, using a Potter spray tower to apply of the oil. The egg of P. persimilis was the least susceptible stage (LC₅₀ 444.84) and its LC₅₀ was significantly higher than all other stages tested of either P. persimilis or T. urticae . The LC₅₀ for adult female T. urticae (LC₅₀ 63.89) was significantly lower than the larva (LC₅₀ 93.86); however, there was no significant difference in response between the protonymph (LC₅₀ 70.44) and the larva, which were both higher than T. urticae eggs (LC₅₀ 17.55). LC₅₀s for P. persimilis larva (LC₅₀ 43.87), protonymph (LC₅₀ 41.55) and adult female (LC₅₀ 53.34) were similar. Scanning electron microscopy showed that the egg surface of T. urticae is usually well covered with fine silk that may trap more oil and increase AMO efficacy. Other possible differences in AMO efficacy between T. urticae and P. persimilis may be due to differences in egg size, egg incubation period, egg surface structure and the presence of vulnerable respiratory cones in T. urticae eggs. Dose of 0.2–0.3% (w/w) is considered to be the most appropriate for n C24 AMOs use against T. urticae in combination with P. persimilis in integrated pest management programs.     

Inheritance of resistance and cross resistance pattern in indoxacarb-resistant diamondback moth Plutella xylostella L.

Leaf-dip assay of Plutella xylostella against indoxacarb showed that the concentration that produced 50% mortality (LC₅₀) of indoxacarb ranged from 20.1 to 11.9 ppm, with highest in Nasik and lowest levels in Coimbatore strains. In selection studies, the LC₅₀ of indoxacarb was 18.5 ppm at generation 1 (G1), which increased to 31.3-fold (167.8 ppm) resistance after ten exposed generations (G10) as compared to unexposed. The LC₅₀ of quinalphos was 74.4 ppm, which increased to 10.0-fold (631.5 ppm) resistance after G10. The LC₅₀ of cypermethrin resistant strain resulted in an 11.5-fold increase in resistance after G10. In P. xylostella , heritability (h²) after ten generations of selection was estimated at 0.4. The number of generations required for tenfold increase in LC₅₀ (1/R) were 6.7. The response to indoxacarb selection in P. xylostella was 0.2 and the selection differential was estimated as 0.4. The phenotypic standard deviation was 0.2. Reciprocal crosses between indoxacarb-resistant and susceptible strains showed that the inheritance of indoxacarb resistance was autosomal. The degree of heritability (D_LC) (0.4, 0.4) indicated incomplete recessive inheritance of indoxacarb resistance.     

The effectiveness of sodium lauryl sulphate as a shark repellent in a laboratory test situation

Swim-through chemical repellency tests, using sodium lauryl sulphate (SLS), cupric acetate, and rotenone, were conducted in a specially-designed roundabout tank on horn sharks, Heterodontus francisci , swell sharks, Cephaloscylliun ventriosum , and leopard sharks, Triakis semifasciata . Effective concentration thresholds (EC₅₀s) were calculated for two levels of response: (1) minimum noticeable and (2) strong. The SLS EC₅₀s were: horn shark 43.6 and 174.5 ppm; swell shark 95.1 and 160.0 ppm; and leopard shark inconclusive and 113.1 ppm. No response was discernible from cupric acetate. Rotenone evoked a weak response with an EC₅₀ of 5.7 ppm, but no strong response.
The ratio of the minimum noticeable EC₅₀: 24-hour lethal concentration (LC₅₀) indicated the relative repellency (compared to toxicity) of the chemicals. The ratio for SLS was 19:1 and for rotenone 57:1. SLS did not provoke a repellency response at a low enough concentration to function effectively as a classical, surrounding-cloud type, repellent. The range of potency of SLS, however, does allow it to be used as a directional repellent.     

Susceptibility of various developmental stages of the maize weevil, Sitophilus zeamais Motschulsky (Col., Curculionidae) to methyl iodide in brown rice

Abstract:  The efficacy of methyl iodide (MI) as a fumigant against all developmental stages of the maize weevil, Sitophilus zeamais Motsch. was investigated. Tests were conducted with concentrations of 1.5, 1.8, 2.1, 2.4, 2.7 and 3.0 mg/l, for a 6-h exposure period. Values of LC₅₀, LC₉₅ and LC₉₉ of MI for immatures and adult stages were determined. The present laboratory tests showed that MI was toxic to various life stages of S. zeamais at relatively short exposure periods. At the LC₅₀ and LC₉₅ levels, the most susceptible stage was the egg stage followed by larvae, pupae and adults (1-day mortality). The egg was found to be most susceptible to MI, requiring 0.81 and 2.16 mg/l for 50 and 99% mortality, respectively, while the adult was most tolerant, requiring 2.30 and 3.02 mg/l for 50 and 99% mortality, respectively, based on 1-day mortality count. Pupae were less susceptible to MI than egg and larvae, requiring 1.47 and 3.19 mg/l for 50 and 99% mortality, respectively. Based on the present toxicity tests, MI has the potential for use as a fumigant to control all developmental stages of the maize weevil, S. zeamais .     

Insecticide susceptibility and resistance of larvae of the Anopheles sinensis Group (Diptera: Culicidae) from Paju, Republic of Korea

The susceptibility of members of the Anopheles sinensis Group in Korea to insecticides was evaluated under laboratory conditions using 15 insecticides currently used by local public health centers in Korea. The insecticides included eight pyrethroids, six organophosphates and a pyrazol analogue. Based on their LC₅₀ values, the order of susceptibility of An. sinensis larvae to the insecticides was bifenthrin, chlorfenapyr, α-cypermethrin and λ-cyhalothrin, with values of 0.009, 0.04, 0.06 and 0.08 p.p.m., respectively. The least susceptibility was obtained with fenitrothion, with an LC₅₀ of 7.7 p.p.m. In the comparative resistance test, the resistance ratios (RR) of 14 insecticides were compared to each other using two strains of members of the An. sinensis Group collected in the locality in 2001 and 2008. Anopheles spp. demonstrated higher RR to organophosphates such as fenthion, and low RR for the pyrethroids. Among the organophosphates, fenthion had the highest RR of 33.3 and 270.0 fold differences for LC₅₀ and LC₉₀ values, respectively. Among the pyrethroids, permethrin was observed to have the highest RR of 3.8 and 1.8 fold differences for LC₅₀ and LC₉₀ values, respectively. However, there were no significant differences in susceptibility to chlorfenapyr, chlorpyrifos, deltamethrin and fenitrothion. An. sinensis s. l. was more susceptible to the six insecticides bifenthrin, λ-cyhalothrin, α-cypermethrin, cypermethrin, cyfluthrin and pyridafenthion, showing 0.03, 0.06, 0.3, 0.3, 0.4 and 0.4 fold differences in resistance rates (RR LC₅₀), respectively.     

The toxicity of iron to brown trout and effects on the gills: a comparison of two grades of iron sulphate

The 96-h LC₅₀ on brown trout Salmo trutta of a commercial iron (III) sulphate liquor, used for treating reservoirs to reduce algal growth, was 28 mg total Fe l⁻¹ (0·05 mg soluble Fe l⁻¹). The 96-h LC₅₀ for analar grade iron (III) sulphate was 47 mg total Fe l⁻¹ (0·24 mg soluble Fe l⁻¹). Lethal and sublethal exposure to both grades of iron resulted in accumulation on the gill, which appears to be the main target for iron toxicity. Greater iron accumulation occurred during exposure to commercial iron sulphate liquor. Physical clogging of gills and gill damage was seen during lethal and sublethal exposure to iron. Gill tissue analysis showed no evidence of iron uptake into gill tissues during lethal or sublethal exposure to iron. Iron did not accumulate in plasma of fish exposed to iron compared to controls. Respiratory disruption due to physical clogging of the gills is suggested as a possible mechanism for iron toxicity.     

Positive correlation of methamidophos resistance between Lipaphis erysimi and Diaeretilla rapae and effects of methamidophos ingested by host insect on the parasitoid

Temporal and spatial correlated variations on the methamidophos resistance and biomolecular rate constant of acetylcholinesterase to insecticides were found between the turnip aphid, Lipaphis erysimi and its endoparasitoid, Diaeretilla rapae , collected from field colonies and an insecticide-free field insectarium in Fujian, China. Compared to the related susceptible insectarium population, L. erysimi and D. rapae displayed 7.4–29.2- and 2.6–9.2-fold resistance ratios, respectively. In addition, two populations of L. erysimi with different methamidophos resistance levels, that is, a field (with 5.8-fold resistance ratio) and an insectarium population, were used to study the effects of methamidophos ingested by the host insect on D. rapae development. The percentage of D. rapae cocoon formation decreased significantly when the parasitized L. erysimi were fed on cauliflower leaves treated with methamidophos at lethal concentration dosages 10 (LC₁₀) or LC₅₀. At LC₅₀ dosages the percentage of D. rapae cocoon formation and adult emergence decreased significantly. When the parasitized L. erysimi were fed on methamidophos at LC₉₀ dosage, no D. rapae cocoons were found. When the field or insectarium L. erysimi were treated with methamidophos at LC₁₀, the susceptibility to methamidophos in the adult D. rapae emerged from the treated host insect was similar to the control. However, the susceptibility to methamidophos in the adult D. rapae became lower than the control when the host insects were treated at LC₅₀ dosages. The data thus suggested that the methamidophos ingested by the host insect L. erysimi could be an important factor in the endoparasitoids' insecticide resistance development. The natural selectivity would favor the parasitoids that had developed an insensitivity to the insecticide(s).     

Morphological changes in the gills of Lophiosilurus alexandri exposed to un-ionized ammonia

The average lethal concentration of un-ionized ammonia (48-h LC₅₀NH₃) has been determined by the static assay for larvae (0.48 mg l⁻¹) and alevins (0.92 mg l⁻¹) of 'pacamã' Lophiosilurus alexandri. Studies by light and scanning electron microscopes at the greatest concentration of NH₃ (0.99 mg l⁻¹ for larvae and 1.5 mg l⁻¹ for alevins) have shown that the changes in the cells and branchial tissue were more intense in the alevins.     

Synthesis and Cytotoxic Profile of a Diphtheria Toxin-Neurotrophin-4 Chimera

Abstract: A diphtheria toxin-neurotrophin-4/5 (NT-4/5) chimera (DAB₃₈₉-NT4), in which the native receptor binding domain of diphtheria toxin was replaced with a synthetic gene encoding rat NT-4/5, was expressed, refolded, and purified. This fusion toxin has a deduced molecular mass of 60,163 and is formed by joining the first 389 amino acids of diphtheria toxin to amino acids 1–130 of mature rat NT-4/5, using an NH₂-terminal bridge of 33 additional amino acids including six consecutive histidines. Neural cell types expressing only p75^LNGFR or p75^LNGFR and full-length or truncated TrkB were used to evaluate the cytotoxic efficacy of DAB₃₈₉-NT4. The fusion toxin produced a concentration-dependent killing of all cell populations, with LC₅₀ values that largely reflected the known NT-4/5 binding affinities for these receptor proteins. Mean LC₅₀ values ranged from 2,960 p M in p75^LNGFR-expressing neuro-2a neuroblastoma cells to 1,075 and 70 p M , respectively, in hippocampal astrocytes (p75^LNGFR+/truncated TrkB⁺) and cerebellar granule cells (p75^LNGFR+/TrkB⁺). The LC₅₀ for DAB₃₈₉-NT4 in receptor-negative 3T3 fibroblasts was 20 n M . NT-4/5 and brain-derived neurotrophic factor but not ciliary neurotrophic factor added in excess neutralized DAB₃₈₉-NT4 cytotoxicity. NT-4/5, however, did not reduce the cytotoxicity of intact diphtheria toxin.     

Ovicidal and larvicidal effectiveness of several insect growth inhibitors and regulators on the codling moth Cydia pomonella L. (Lep., Tortricidae)

Several insect growth inhibitors (IGIs) and regulators (IGRs) were tested in the laboratory for their ovicidal and larvicidal properties on the codling moth C. pomonella , by dipping apples in solutions of them. The IGIs which block chitin synthesis – diflubenzuron, hexaflumuron and teflubenzuron – were noticeably more effective against eggs than on newborn larvae with preventive ovicidal 50% lethality concentrations (LC₅₀) values of approximately 0.6, 1.3 and 15 p.p.m., respectively, and larvicidal LC₅₀ values of 104, 1208 and 204 p.p.m. Flufenoxuron, on the other hand, is almost as effective on larvae (LC₅₀ : 9.9 p.p.m.) as on eggs (LC₅₀ : 5.4 p.p.m.). Fenoxycarb, an IGR juvenile hormone analogue, acts as an excellent ovicidal product with an LC₅₀ value of 0.05 p.p.m. Tebufenozide, an IGR ecdyson (moulting hormone) agonist, is exclusively larvicidal with an LC₅₀ at 0.4 p.p.m. Methoxyfenozide, an IGR of the same family and currently being developed, acts as effectively on eggs as on larvae with ovicidal and larvicidal LC₅₀ values of about 0.6 and 0.8 p.p.m., respectively. When ovicidal products are applied as a curative treatment on eggs less than 24 h old, their effectiveness is much lower than that obtained from preventive application.     

Laboratory culture conditions affect stability of resistance to Bacillus thuringiensis Cry1Ac in Plutella xylostella (Lep., Plutellidae)

Abstract:  Populations of Plutella xylostella L. with high (laboratory re-selected) and low levels (unselected) of resistance to the Bacillus thuringiensis ( B.t. ) toxin Cry1Ac were maintained under controlled environment conditions in the absence of any further selection pressure. Larvae were maintained either in discrete generations on freshly excised leaves replaced ad lib (standard culture system) or in microcosm cages holding up to 12 potted Chinese cabbage plants, allowing progressively overlapping generations of insects. After 12 generations in the microcosm cages, the LC₅₀ values of both selected and unselected populations were not significantly different from those of a standard susceptible population. Under standard culture conditions, the LC₅₀ value for unselected insects after 12 generations was almost identical to that of unselected insects in the microcosm cages, whereas the LC₅₀ value for selected insects was 1250-fold greater. The fecundity of the selected population was significantly lower compared with that of the same population in the microcosm cages after 12 generations. There was no significant change in the fecundity of the unselected population after 12 generations in the microcosm cages. The results show, that differences in the culture system (microcosm vs. standard) and in the resistance level (re-selected vs. unselected) can have a marked influence on the stability of resistance to a B.t. toxin in an insect population. Possible factors involved in determining the rate at which resistance declines are discussed.     

Genetics of Indoxacarb resistance in Helicoverpa armigera (Hubner)

The present investigation was done with the aim of studying the genetics of Indoxacarb resistance. Selection of Helicoverpa armigera (Hubner) with Indoxacarb was done for eight generations to develop resistance. Reciprocal crosses between resistant and susceptible populations were made to understand the population genetics of Indoxacarb resistance in H. armigera . Generation-wise selection with Indoxacarb was evaluated for resistance development in H. armigera . The LC₅₀ of Indoxacarb was 2.81 p.p.m. for the first selected generation, and it increased to 272.55 p.p.m. after eight selected generations, which is a 1238.86-fold resistance compared to the susceptible strain. The estimated realized heritability (h²) after eight generations of selection with Indoxacarb was 0.45. The number of generations required for a tenfold increase in LC₅₀ (1/R) was estimated to be 2.59. The response to Indoxacarb selection in H. armigera was 0.39, the estimated selection differential (S) was 0.87, and the phenotypic standard deviation (σp) was 0.03. Reciprocal crosses between Indoxacarb resistant and susceptible strains revealed that the inheritance of Indoxacarb resistance was autosomal: neither maternal effect nor linkage was evident. The values of D_LC (0.10 and 0.09) indicated completely recessive inheritance of Indoxacarb resistance.     

Baseline toxicity of emamectin and spinosad to Helicoverpa armigera (Lepidoptera: Noctuidae) for resistance monitoring

Acute toxicity studies of emamectin and spinosad against Helicoverpa armigera revealed that the pest is highly susceptible to both the insecticides. The median lethal dose (LD₅₀) of emamectin is 3.86 × 10⁻³ µg per larva. The median lethal concentrations (LC₅₀) of emamectin and spinosad were found to be 0.09 and 2.94 ppm, respectively. The discriminating doses were fixed based on the LC₉₅ of the susceptible population of H. armigera as 0.80 ppm for emamectin and 10 ppm for spinosad. Resistance was not observed when the discriminating doses of emamectin and spinosad were applied on field-collected populations of H. armigera from two intensive cotton growing areas, Coimbatore and Madurai, India.     

Seasonal and geographical toxicity of Indoxacarb against Helicoverpa armigera and influence of different host plants against Indoxacarb in India, 2005–2007

Indoxacarb, an oxadiazine insecticide, was evaluated for its effectiveness against Helicoverpa armigera collected from selected locations in India. Determination of Indoxacarb efficacy was done using a log-dose probit (LDP) bioassay against third instars collected from cotton ( Gossypium arborium ) fields near Akola, India. Monthly levels of toxicity of Indoxacarb were determined from July 2005 to March 2007. The maximum tolerance level of Indoxacarb was reported for the Amaravati strain (5.09 p.p.m.) and the minimum tolerance level for the Fatehbad strain (0.22 p.p.m.). Seasonal monitoring of Indoxacarb toxicity revealed an increased trend in tolerance from July 2005 to February 2006, which decreased from March 2006. The LC₅₀ of Indoxacarb was 2.71 p.p.m. in July 2005 and 17.14 p.p.m. in February 2006. During 2006–2007, the LC₅₀ was 3.84 p.p.m. at the start of the season and in March 2007 it was 13.51 p.p.m. The minimum LC₅₀ of Indoxacarb was reported for H. armigera larvae fed on Legasca spp. (1.62 p.p.m.) and the maximum LC₅₀ was reported for H. armigera reared on chickpea ( Cicer arietium ) (8.45 p.p.m.). LC₅₀ of 2.73 and 4.56 p.p.m. were reported for H. armigera fed on cotton ( Gossypium arborium ) and pigeonpea ( Cajanus cajan ), respectively.     

The disruption of sodium balance in brook charr, Salvelinus fontinalis (Mitchill), by manganese and iron

A primary toxic action of manganese to brook charr, Sulvelinusjonfinalis, at concentrations near or above the 96 h LC₅₀ was the disruption of sodium regulation. Body and plasma sodium concentrations of brook charr declined by 52 and 40%, respectively, during exposure to 10.9 mM manganese (in 250 PM CaCI), and all fish died within 36 h. Sodium balance was less severely affected by 2.7 and 5.5 mM manganese. An increase in the external calcium concentration from 0.05 to 1.0 mM raised the LC₅₀ for manganese from 4.9 to 5.8 mM, and a further increase to 2.5 mM calcium almost doubled it to 10.2 mM. An examination of stable manganese uptake by the gills revealed that accumulation was inversely correlated with body sodium concentration (r =−0.77). Radioactive J4Mn entered the bloodstream in low levels and accumulated in the liver. Thus manganese may have systemic effects as well as those attributable to surface binding on the gill. Studies of the mechanism ofdissolved iron toxicity were less conclusive, but it did not appear to involve extensive disruption of sodium balance. There was about a 15% drop in body sodium concentration when the trout were exposed for 48 h to the 96 h LC₅₀ level of iron, but plasma sodium was unaffected. Also, an iron concentration at twice the LC₅₀ did not escalate the loss of body sodium, and increasing the water calcium concentration did not raise the LC₅₀.     

Production of mosquito larvicidal Bacillus thuringiensis serotype H-14 on raw material media from Nigeria

Bacillus thuringiensis serotype H-14 de Barjac, a potent larvicide of many mosquito and blackfly species, was grown on various media compounded from fermented cassava ( Mannihot esculenta ), ground and whole maize ( Zea mays ) grains and whole cowpeas ( Vigna unguiculata ) in shake flask fermentations. The liquors obtained from 100g/l of the whole cowpea and maize grains as well as combinations of these were used for further fermentations in 1 and 5 1 fermenters. The final whole cultures obtained were bioassayed against L11/111 of Aedes aegypti and the concentration-effects estimated. The potency of the preparations (estimated as LC₅₀, strength that showed 50% mortality of the mosquito larvae) ranged from 10.5 mg/l for the 1:3 combination of cowpea steep liquor:maize steep liquor to 90 mg/l for the 2:1 combination at 95% confidence limits. The LC₅₀ of a standard nutrient broth-yeast extract medium was 18 mg/l. The juice of Citrus aurantifolia and an extract from Elaeis guiniensis were used as acid and alkali respectively while bleached deodorized palm olein was used as antifoam.     

Treated Filter Paper Bioassay for Detection of Insecticide Resistance in Haematobia irritans exigua de Meijere (Diptera: Muscidae)

This paper reports on the standardisation of an assay, whereby buffalo flies Haematobia irritans exigua de Meijere from a laboratory population which had not been exposed to insecticides for 8 years were confined in Petri dishes containing filter paper treated with known concentrations of insecticide. Mortality was assessed after 2 and 4 h and mean LC₅₀ and LC₉₉ values for each of 11 insecticides were calculated. the bioassay technique had acceptable repeatability and was simple to perform. Field populations of northern Queensland buffalo fly were assayed using the technique and were found to have high levels of pyrethroid resistance and little or no organophosphate resistance.     

Expression of mel gene improves the UV resistance of Bacillus thuringiensis

Aims:  To improve ultraviolet (UV) resistance of Bacillus thuringiensis for increasing the duration of the Bt product applied in the field, a genetically engineered strain Bt TD841 that produced both melanin and Cry1A protein was constructed, and its UV resistance was evaluated in the laboratory.
Methods and Results:  Melanin quantitative analysis revealed that the recombinant strain Bt TD841 could synthesize 0.15 mg melanin ml⁻¹ sporulated culture. Atomic force microscopy confirmed the production of diamond crystal and SDS-PAGE results showed the expression of the 130 kDa Cry1A protein. Bioassay results demonstrated that the LC₅₀ value of Bt TD841 was 3.69 μl ml⁻¹ against Helicoverpa armigera and the UV resistance of this recombinant was enhanced 9.7-fold compared to its parental strain Bt HC42 after 4-h UV irradiation.
Conclusion:  Expression of the mel gene can significantly increase UV resistance of B. thuringiensis.
Significance and Impact of the Study:  This is the first report on genetically engineered Bt strain with co-expression of melanin and the insecticidal crystal proteins gene, and the results may offer a practical solution for improving the photoprotection of Bt products in field application.     

Annual changes in the nutritive state of North Sea dab

The nutritive state of dab Limanda limanda was investigated over a 2-year period at a fixed sampling site northwest of Helgoland (German Bight, North Sea), with respect to feeding habits and the accumulation of biochemical storage products. Ophiuroids formed the main weight of food organisms (50%) while polychaetes (10%), molluscs and crustaceans (<5% each) were less frequent. Feeding activity in males varied between summer and winter, while females fed more constantly. The condition factor and the hepatosomatic index showed characteristic seasonal cycles in both sexes. The glycogen content in the liver reached 40–60 mg g⁻¹ FW in summer and fell to about 10–20 mg g⁻¹ FW in late winter. Total lipids of the liver showed a distinct seasonal cycle with 400 mg g⁻¹ FW in summer and a minimum of 50–100 mg g⁻¹ FW in spring. The lipid content of the muscle ranged from 5 to 6 mg g⁻¹ FW and did not vary significantly between seasons.