Efficiency of herbivore exclusion by ants attracted to aphids on the vetch <Emphasis Type="Italic">Vicia angustifolia</Emphasis> L. (Leguminosae)

The efficiency of herbivore exclusion by ants on the vetch Vicia angustifolia L. (Leguminosae) with extrafloral nectary, mediated by ant attraction to aphids was investigated in a field census and laboratory experiments. In the field, workers of Lasius japonicus Santschi and Tetramorium tsushimae Emery frequently visited plants of the vetch parasitized by aphids of Aphis craccivora Koch, but only a few workers visited plants without aphids. An increase in the number of ants visiting a plant with increasing numbers of aphids caused a decrease in the number of larvae of the weevil, Hypera postica Gyllenhal. Therefore, the efficiency of herbivore exclusion by ants was higher on plants parasitized by Ap.craccivora aphids than that on plants unparasitized by aphids. In the laboratory experiments, L.japonicus workers frequently patrolled not only shoots with Ap.craccivora aphids but also shoots without them. However, T.tsushimae workers visited mainly shoots with Ap.craccivora aphids but less frequently on shoots without aphids. Therefore, L.japonicus workers excluded herbivores more efficiently on plants of the vetch than T.tsushimae workers. Consequently, the efficiency of herbivore exclusion by ants on the vetch can be influenced directly by differences in ant species and indirectly by the presence of aphids on plants. The present study highlights the significance of indirect interactions between ants and plants with extrafloral nectary, mediated by ant attraction to aphids for herbivore exclusion of plants.     

Age‐dependent investment in death‐feigning behaviour in the sweetpotato weevil Cylas formicarius

Because life‐history theory predicts that risky behaviours such as mating should increase as life expectancy decreases, predatory avoidance is expected to decrease with age. However, this prediction has not been examined. In the present study, the effect of age on death‐feigning behaviour, a form of predatory avoidance behaviour in the sweetpotato weevil Cylas formicarius (Summers) (Coleoptera: Brentidae), is investigated by performing a longitudinal study. Because the effects of mating history and age usually cannot be distinguished, mating history is controlled. The results show that only female weevils decrease the investment in death‐feigning behaviour with age, whereas male weevils do not show any age‐related change. In addition, death‐feigning behaviour of mated females is longer than that of virgin females, possibly because additional mating partners would be not needed by mated females.     

The use of honeydew in foraging for aphids by larvae of the ladybird beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Abstract.  1. To clarify the use of honeydew in foraging for aphids by larvae of the ladybird beetle, Coccinella septempunctata L., searching behaviour of ladybird larvae for Aphis craccivora Koch and Acyrthosiphon pisum Harris and the abundance of honeydew under aphid colonies were examined in laboratory experiments.
2. More larvae responded by climbing the plants with aphids than responded to plants without aphids. When the plants were replaced with sticks, in order to exclude visual and olfactory cues from plants and aphids, more larvae of C. septempunctata climbed sticks above the area that contained honeydew than climbed sticks above the area that did not contain honeydew. Then, ladybird larvae use honeydew as a contact kairomone when foraging for aphids.
3.  Aphis craccivora deposited a larger number of honeydew droplets beneath the plants than did similar numbers of A. pisum. Thus, C. septempunctata larvae licked more frequently the honeydew of A. craccivora than that of A. pisum and spent longer searching on the area containing honeydew of A. craccivora than that of A. pisum . Consequently, a larger number of larvae climbed a stick above honeydew of A. craccivora than that of A. pisum.
4. It may be also considered that C. septempunctata larvae can distinguish honeydew of the two aphid species and respond more strongly to A. craccivora than A. pisum.     

DWARF50 (D50), a rice (Oryza sativa L.) gene encoding inositol polyphosphate 5‐phosphatase,is required for proper development of intercalary meristem

Rice internodes are vital for supporting high‐yield panicles, which are controlled by various factors such as cell division, cell elongation and cell wall biosynthesis. Therefore, formation and regulation of the internode cell‐producing intercalary meristem (IM) are important for determining the shape of internodes. To understand the regulation of internode development, we analysed a rice dwarf mutant, dwarf 50 (d50). Previously, we reported that parenchyma cells in the elongated internodes of d50 ectopically deposit cell wall phenolics. In this study, we revealed that D50 encodes putative inositol polyphosphate 5‐phosphatase (5PTase), which may be involved in phosphoinositide signalling required for many essential cellular functions, such as cytoskeleton organization, endocytosis and vesicular trafficking in eukaryotes. Analysis of the rice genome revealed 20 putative 5PTases including D50. The d50 mutation induced abnormally oriented cell division, irregular deposition of cell wall pectins and thick actin bundles in the parenchyma cells of the IM, resulting in abnormally organized cell files of the internode parenchyma and dwarf phenotype. Our results suggest that the putative 5PTase, encoded by D50, is essential for IM formation, including the direction of cell division, deposition of cell wall pectins and control of actin organization.     

Effects of elevated CO2 on the size structure in even-aged monospecific stands of Chenopodium album

To investigate the effect of elevated CO₂ on the size inequality and size structure, even‐aged monospecific stands of an annual, Chenopodium album, were established at ambient and doubled CO₂ with high and low nutrient availabilities in open top chambers. The growth of individual plants was monitored non‐destructively every week until flowering. Elevated CO₂ significantly enhanced plant growth at high nutrients, but did not at low nutrients. The size inequality expressed as the coefficient of variation tended to increase at elevated CO₂. Size structure of the stands was analyzed by the cumulative frequency distribution of plant size. At early stages of plant growth, CO₂ elevation benefited all individuals and shifted the whole size distribution of the stand to large size classes. At later stages, dominant individuals were still larger at elevated than at ambient CO₂, but the difference in small subordinate individuals between two CO₂ levels became smaller. Although these tendencies were found at both nutrient availabilities, difference in size distribution between CO₂ levels was larger at high nutrients. The CO₂ elevation did not significantly enhance the growth rate as a function of plant size except for the high nutrient stand at the earliest stage, indicating that the higher biomass at elevated CO₂ at later stages in the high nutrient stand was caused by the larger size of individuals at the earliest stage. Thus the effect of elevated CO₂ on stand structure and size inequality strongly depended on the growth stage and nutrient availabilities.     

Phylogenetic Relationships Among Microsporidia Based on rDNA Sequence Data, With Particular Reference to Fish-Infecting Microsporidium Balbiani 1884 Species.

Recently, large discrepancies have been identified between microsporidian systematics based on molecular and traditional characteristics. In the current study the 530f-580r region of the rRNA gene of eight microsporidian species was cloned and sequenced. Included were two unclassified species of Microsporidium Balbiani, 1884 and an unidentified microsporidian that infects the musculature of different sea bream species. Sequence identities in excess of 98% indicated that these three species almost certainly are members of the same genus. Phylogenetic analyses of all microsporidian sequence data available for this region of the gene (20 species) and for partial small subunit sequences (51 species of 21 genera) revealed these species to be distinct from the family Pleistophoridae Doflein, 1901 and closely related them to the genus Sproguea Weissenberg, 1976. This clade was found to comprise a sister taxon to that containing the vast majority of fish-infecting species. Broad cladistic divisions were found between terrestrial insect-infecting and fish-infecting species, which together are distant from the aquatic insect-infecting microsporidia. The rRNA gene of certain fish-infecting genera was found to be more highly conserved than previously reported. This has implications for its utility in diagnostic assays and phylogenetic studies at, or close to, the species level.     

Evidence of autumn overseas migration in the rice planthoppers, Nilaparvata lugens and Sogatella furcifera: analysis of light trap catches and associated weather patterns

ABSTRACT. 1. Daily trap catches of the rice planthoppers, N.lugens Stal and S.furcifera Horvath, and associated synoptic weather patterns were analysed in Kyushu, south-west Japan, in the autumns of 1980–85.
2. Certain weather patterns which seemed to favour overseas immigration, were reflected in trap catches: of eighteen occasions in which back-tracks on 850 mbar wind fields reached central China, marked mass catches in a light trap occurred on six occasions, and peaks in catch curves were found on another seven occasions.
3. These results strongly imply overseas immigration of the planthoppers from China to Kyushu in autumn, identical to invasions by the same species in early summer. However, such autumn migration is apparently non-adaptive because migrants or their progeny are soon killed by cold weather.     

Phorbol esters as probes of the modulatory site on protein kinase G–an overview

Phorbol esters as probes of the modulatory site on protein kinase C–an overview. The phorbol esters, diterpene derivatives produced by members of the family Euphorbiaceae, are of major scientific importance as tumour promoters. Their primary site of action is protein kinase C, an enzyme involved in the message transduction pathway for a large class of hormones which cause enhanced phosphatidylinositol turnover. Heterogeneity in the response of biological systems to the phorbol esters may be explained in part by heterogeneity in the phospholipids associated with protein kinase C, in its subcellular localization, and by proteolytic processing, as well as by isoforms of the enzyme. Development of other classes of activators of protein kinase C through computer modelling and natural product isolation suggests possible new approaches for intervention in the pathway.     

Failure of Immunological Memory in DMBA-treated Mice

SEVERAL chemical carcinogens show immunosuppressive activity in various experimental systems^1–4. Stjernswärd⁵ reported a remarkable correlation between carcinogenic activity and immunosuppressive capacity of chemicals, that is, potent carcinogens such as 3-methylcholanthrene (MCA), benz(a)pyrene and 7,12-dimethylbenzanthracene (DMBA) suppressed the immune response to sheep red blood cells (SRBC) but noncarcinogenic analogues did not. Stutman² showed that administration of MCA depressed the immune response to SRBC in mice (C3Hf/Bi strain) sensitive to oncogenic effect of the drug, but the drug was not immunosuppressive in the I strain, which is relatively resistant to its oncogenic effect. These suggest an important role of immunosuppressive activity of the carcinogens on the process of carcinogenesis, perhaps by weakening the immune surveillance capacity of the host. On the other hand, many potent carcinogens, such as urethane, do not seem to have an immunosuppressive effect⁶. Here we have analysed the effect of DMBA on the antibody response of C3H/He mice to soluble protein antigen, bacterial α-amylase (BαA). Our findings suggest a marked effect of DMBA on the immunological memory.