Host-attacking behavior of a eulophid parasite,Kratochviliana sp., to the leaf mining host,Phytomyza ranunculi (Diptera: Agromyzidae) during its stay on the leaf

The present paper studies how the female parasite of Kratochviliana sp. visits and attacks its host larvae of Ranunculus leaf mining fly, P. ranunculi at a single leaf visit. The parasite visited its hosts at random on the leaf. The frequency of host visits was independent of the host density and the proportion of hosts survived from the parasite attack, in a leaf and its distribution was expressed as a single straight line. It almost always attacked living hosts at the first host visit after isolated from them for one day but with the rate of about 0.5 at the subsequent visits. In consequence, the relationships of the number of host attacks and killed hosts to the host density drew satulated curves in each. A model of host attack by this parasite at its single leaf visit was formulated by modifyingBakker et al.'s model (1972) basing upon these observations and the attack avoidance by the parasite to already attacked hosts previously reported.     

Yeast thioredoxin-enriched extracts for mitigating the allergenicity of foods

Thioredoxin (TRX) catalyzes the reduction of disulfide bonds in proteins via the NADPH-dependent thioredoxin reductase system. Reducing the disulfide bonds of allergenic proteins in food by TRX lowers the allergenicity. We established in this study a method to prepare TRX-enriched extracts from the edible yeast, Saccharomyces cerevisiae, on a large and practical scale, with the objective of developing TRX-containing functional foods to mitigate food allergy. Treating with the yeast TRX-enriched extracts together with NADPH and yeast thioredoxin reductase enhanced the pepsin cleavage of β-lactoglobulin and ovomucoid (OM). We also examined whether yeast TRX can mitigate the allergenicity of OM by conducting immediate allergy tests on guinea pigs. The treatment with TRX reduced the anaphylactic symptoms induced by OM in these tests. These results indicate that yeast TRX was beneficial against food allergy, raising the possibility that yeast TRX-enriched extracts can be applied to food materials for mitigating food allergy.     

Foraging for patchily-distributed leaf-miners by the parasitoid,Dapsilarthra rufiventris (Hymenoptera: Braconidae). II. Stopping rule for host search

We studied the stopping rule which the female parasitoid,Dapsilarthra rufiventris, uses for deciding when to leave the leaflet on which she is searching for leaf-mining larvae,Phytomyza ranunculi. She is unlikely to employ some current stopping rules, such as fixed-number and fixed-time rules and others. The searching female appears to deposit a marking pheromone on the leaflet. We formulated a model for predicting the amount of pheromone accumulated on the leaflet. The model assumes that she will deposit the pheromone on the leaflet at a given rate (a) per unit time which is proportional to search speed, and will leave it when the amount of pheromone reaches the thresholdL. In this modelL denotes the amount of the search effort spent on the leaflet. The model was fitted fairly well to the data. A comparison of the observed results with the predictions of the model suggests thatL increases markedly at the first encounter with the mine and at a lower rate for the subsequent encounters. This appears to be a kind of area-concentrated search, that is, searching for hosts for a while in the immediate vicinity after finding one host, and would be adaptive in foraging forP. ranunculi larvae, which exhibit clumped distributions among leaflets in the field.     

Foraging for patchily-distributed leaf miners by the parasitic wasp,Dacnusa sibirica

We studied the rules used by the female parasitoid, Dacnusa sibirica Telenga (Hymenoptera: Braconidae), for deciding when to leave a tomato leaflet on which she is searching for larvae of the leafminer, Liriomyza bryoniae Kalt. (Diptera: Agromyzidae). Females would deposit a marking pheromone on the leaflet and would leave the leaflet when the amount of the pheromone accumulated to the threshold L, which is proportional to the amount of search effort on the leaflet. L appears to increase with host density since it rises after every encounter with a host (or mine).D. sibirica would employ an area-concentrated search, which is advantageous in foraging for hosts showing a clumped distribution.     

Column Chromatographic Separation of Chlorophyllide {alpha} and Pheophorbide {alpha}

Chlorophyllide a, pheophorbide a, chlorophyll a and pheophytina were separated in a short time by anion-exchange chromatographywith a short column of DEAE-Sepharose CL-6B. (Received February 16, 1984; Accepted April 13, 1984)     

Content of arachidonic and eicosapentaenoic acids in polar lipids from Gracilaria (Gracilariales,Rhodophyta)

Fatty acid composition, especially the distribution of eicosapolyenoic acids in several species of Gracilaria, was analyzed in relation to their taxonomy. The species have been grouped into two types based on distribution of these polyenoic acids: Type 1, which contains palmitic, oleic and arachidonic acids as the major components, and Type II, which contains eicosapentaenoic acid in addition to Type I fatty acids. Octadecapolyenoic acids were detected only in trace amounts in each Type. A similar remarkable difference also was observed in the fatty acid composition of lipid classes. The major component of eicosapolyenoic acids in Type I was arachidonic acid in all lipid classes. In Type II, eicosapentaenoic acid was the major component in monogalactosyl diacylglycerol, digalactosyl diacylglycerol, sulfoquinovosyl diacylglycerol and phosphatidylglycerol. Arachidonic and eicosapentaenoic acids were contained in large amounts in Type II phosphatidylcholine. Grouping of Gracilaria species into Type I and Type II is not entirely consistent with morphological and taxonomic features, but the difference in fatty acid composition is likely due to genetic rather than to environmental factors.     

Models of the spatial pattern of egg population of Ranunculus leaf mining fly,Phytomyza ranunculi (Diptera: Agromyzidae), in host leaves

This paper considers two kinds of model of the spatial pattern of egg distribution of the Ranunculus leaf mining fly, Phytomyza ranunculiSchrank , as a step to determining the effect of the distribution upon the parasitism of this species by the eulophid parasite, Kratochviliana sp.. Each model incorporates submodels in several important stages of both the processes of visiting and subsequent oviposition by the fly. Model 2 is more general than model 1, because the former also includes the effect of oviposition restraint. Both models fitted well the egg distribution on fresh plants and on exploited plants. The fitting similarity on exploited plants is due to the fact that there were not so many heavily exploited leaves which lead to oviposition restraint, owing to the low density of mature larvae contained in the leaves. These models will be applicable to the distribution of larvae as well as eggs, because most larvae remain in the leaf where they occurred as eggs, until emerging just before pupation. This paper also discusses by use of these models the fact that this fly tends to effectively avoid excessive oviposition in leaves by laying fewer eggs per visit and visiting leaves more sparsely and also by refraining from further oviposition on leaves exploited heavily by mature larvae.     

Recent trends in nori products and markets in Asia

Since 1960s, modern techniques for nori (Porhyra) cultivation, artificial seeding of conchospores, floatingnet cultivation and freeze storage of nets, have been introduced into Japan, Korea and China. Owing to recent developments of these techniques, mechanization of processing and adaptation of fast-growing varieties of Porphyra, annual yield of nori have increased rapidly. Individual problems have, however, arisen in each country. In Japan, as the result of overproduction of nori, the farmers' profit level has, in general, decreased. As a consequence, the number of nori farmers, especially among those who would enter the industry, has declined markedly, and this is currently a serious problem. In Korea, there is a pressing need to improve the quality of nori, which is more important than increasing production. In China, the technical level of producing high quality Porphyra through cultivation and processing high quality nori is relatively undeveloped. There is thus a critical requirement to develop basic techniques in both cultivation and processing of nori in China.     

Characterization of Sulfoquinovosyl Diacylglycerol from Marine Red Algae

Sulfoquinovosyl diacylglycerol (SQDG) from a red alga, Gracilariaverrucosa, contained high levels of saturated fatty acids, palmiticand myristic acids. The lipid was separated by normal-phasethin-layer chromatography (TLC) into two spots which differedin terms of the color generated by the anthron reagent and interms of constituent fatty acids. However, chromato-graphicand spectrometric (NMR and IR) analyses indicated that boththe upper and the lower fractions were SQDG. The upper fractionwas mainly composed of 20:4/16:0 species, while the major speciesin the lower fraction was mainly 14:0/16:0 and 16:0/16:0. Comparisonof mobilities of SQDG from various sources by TLC confirmedthat the chain length of acyl groups significantly affectedthe Rf value. The short-chain saturated acid species of SQDGwas also detected in marine red algae, Gracilaria textorii,Gelidium amansii, Chondrus ocellatus and Chon-dria crassicaulis. (Received December 9, 1988; Accepted May 10, 1989)