Feeding responses of adult butterflies, Nymphalis xanthomelas, Kaniska canace and Vanessa indica, to components in tree sap and rotting fruits: synergistic effects of ethanol and acetic acid on sugar responsiveness

Exuded tree sap and rotting fruits are important feeding sources for adults of many butterfly species. However, the chemical composition of such rotting foods and the effects of these constituents on butterfly feeding behaviour have rarely been investigated. Chemical analyses revealed that these food sources contain several major components, including fructose, glucose, ethanol and acetic acid. Moreover, 15 amino acids were identified from the exuded tree sap. The gustatory responsiveness to these components was examined in the proboscis of nymphalid adults of three species (Nymphalis xanthomelas, Kaniska canace and Vanessa indica). The first two species primarily feed on sap and rotting fruits, while V. indica frequently visits flowers. Fructose elicited larger feeding responses from these saprophagous butterflies than glucose, which had a feeding-stimulatory effect only on N. xanthomelas at a concentration equivalent to that of the food. Ethanol, acetic acid and the five major amino acids identified in tree sap did not elicit feeding responses by themselves. However, ethanol and/or acetic acid, when mixed with these sugars at equivalent concentrations, evoked feeding and enhanced probing responses in K. canace and V. indica. These results suggest that ethanol and acetic acid, together with sugars at low concentrations, synergistically stimulate butterfly feeding behaviour.     

Maltose fermentation to acetate,CO2 and H2 in the anaerobic hyperthermophilic archaeon Pyrococcus furiosus: evidence for the operation of a novel sugar fermentation pathway

The hyperthermophilic anaerobe Pyrococcus furiosus was grown on maltose as energy and carbon source. During growth 1 mol maltose was fermented to 3–4 mol acetate, 6–7 mol H₂ and 3–4 mol CO₂. The presence of the following enzyme activities in cell extracts of maltose-grown P. furiosus indicate that the sugar is degraded to pyruvate and H₂ by a modified non-phosphorylated Entner-Doudoroff-pathway (the values given in brackets are specific enzyme activities at 100 °C): Glucose: methyl viologen oxidoreductase (0.03 U/mg); 2-keto-3-deoxy-gluconate aldolase (0.03 U/mg); glyceraldehyde: benzyl viologen oxidoreductase (2.6 U/mg), glycerate kinase (2-phosphoglycerate forming) (0.48 U/mg), enolase (10.4 U/mg), pyruvate kinase (1.4 U/mg). Hexokinase, glucose-6-phosphate dehydrogenase, 2-keto-3-deoxy-6-phosphogluconate aldolase and phosphofructokinase could not be detected. Further conversion of pyruvate to acetate, CO₂ and H₂ involves pyruvate: ferredoxin oxidoreductase (0.4 U/mg; T=60°C with Clostridium pasteurianum ferredoxin as electron acceptor), hydrogen: methyl viologen ixodoreductase (3.4 U/mg) and ADP-dependent acetyl-CoA synthetase (1.9 U/mg). Phosphate acetyl transferase and acetate kinase could not be detected. The ADP-dependent acetyl-CoA synthetase catalyzes ATP synthesis via the mechanism of substrate level phosphorylation and apparently constitutes the only ATP conserving site during maltose catabolism in P. furiosus.This novel pathway of maltose fermentation to acetate, CO₂ and H₂ in the anaerobic archaeon P. furiosus may represent a phylogenetically ancient pathway of sugar fermentation.Non-standard abbreviations DTE dithioerythritol - MV methyl viologen - BV benzyl viologen - CHES cyclohexylamino-ethane sulfonic acid - ABTS 2,2-Azino-di-(3-ethylbenzthiazoliumsulfonate)     

Differential effects of sugar-mimic alkaloids in mulberry latex on sugar metabolism and disaccharidases of Eri and domesticated silkworms: enzymatic adaptation of Bombyx mori to mulberry defense

Mulberry leaves (Morus spp.) exude latex rich in sugar-mimic alkaloids, 1,4-dideoxy-1,4-imino-d-arabinitol (d-AB1) and 1-deoxynojirimycin (DNJ), as a defense against herbivorous insects. Sugar-mimic alkaloids are inhibitors of sugar-metabolizing enzymes, and are toxic to the Eri silkworm, Samia ricini, a generalist herbivore, but not at all to the domesticated silkworm, Bombyx mori, a mulberry specialist. To address the phenomena, we fed both larvae diets containing different sugar sources (sucrose, glucose or none) with or without sugar-mimic alkaloids from mulberry latex. In S. ricini, addition of sugar-mimic alkaloids to the sucrose (the major sugar in mulberry leaves) diet reduced both growth and the absorption ratio of sugar, but it reduced neither in B. mori. The midgut soluble sucrase activity of S. ricini was low and inhibited by very low concentrations of sugar-mimic alkaloids (IC₅₀=0.9–8.2 μM), but that of B. mori was high and not inhibited even by very high concentrations (IC₅₀>1000 μM) of sugar-mimic alkaloids. In S. ricini, the addition of sugar-mimic alkaloids to the glucose diet still had considerable negative effects on growth, although it did not reduce the absorption ratio of glucose. The hemolymph of S. ricini fed sugar-mimic alkaloids contained sugar-mimic alkaloids. The trehalose concentration in the hemolymph increased significantly in S. ricini fed sugar-mimic alkaloids, but not in B. mori. The trehalase activities of S. ricini were lower and inhibited by lower concentrations of sugar-mimic alkaloids than those of B. mori. These results suggest that sugar-mimic alkaloids in mulberry latex exert toxicity to S. ricini larvae first by inhibiting midgut sucrase and digestion of sucrose, and secondly, after being absorbed into hemolymph, by inhibiting trehalase and utilization of trehalose, the major blood sugar. Further, our results reveal that B. mori larvae evolved enzymatic adaptation to mulberry defense by developing sucrase and trehalase that are insensitive to sugar-mimic alkaloids.     

Potential non-target impact of Microctonus aethiopoides Loan (Hymenoptera: Braconidae) on Cleopus japonicus Wingelmüller (Coleoptera: Curculionidae), a biocontrol agent for putative release to control the butterfly bush Buddleja davidii Franchet in New Zealand

Abstract  Cleopus japonicus Wingelmüller (Coleoptera: Curculionidae) is being considered for release to control buddleia Buddleja davidii in New Zealand. As part of the pre-release testing, Moroccan and Irish biotypes of the solitary endoparasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae) were evaluated for potential non-target impacts on adult C. japonicus should release occur. Laboratory experiments evaluated both the behavioural and physiological suitability of C. japonicus to both biotypes of the parasitoid. Parasitoid behavioural attraction was assessed using the pathenogenic bacterium Serratia marcescens (Enterobactereaceae), as an indicator of ovipositor penetration. Physiological suitability was assessed by comparing parasitism of C. japonicus with the natural hosts of the respective parasitoid biotypes. The parasitoid-bacteria study showed that C. japonicus was behaviourally acceptable to both Moroccan and Irish M. aethiopoides , with the two experiments producing 34% and 8% mortality, respectively. Cleopus japonicus did not support development of either Moroccan or Irish M. aethiopoides biotypes. None of the weevils dissected at the end of the experiment contained immature parasitoids. Comparison between unexposed and parasitoid-exposed C. japonicus found no difference in premature mortality during the experiment nor in the number of fully reproductive females at its conclusion. The results of this study predict that should C. japonicus be released, the potential impact of M. aethiopoides on field populations will be negligible.