Biomedical subjects

Gerhard Gries

Publications and source records attributed to Gerhard Gries.

5 recordsLinked to original sources

PubMed2003

Does pheromone-based aggregation of codling moth larvae help procure future mates?

In field and laboratory bioassay experiments, we show that larvae of the codling moth, Cydia pomonella, cocoon in aggregations. This aggregation behavior of fifth-instar larvae prior to pupation and arrestment of eclosed adult males by mature female pupae seems to allow mating as soon as an adult female ecloses. This synchronous timing is realized because foraging fifth-instar are attracted by cocoon-spinning larvae and prepupae, but not by pupae, and because male pupae develop faster than female pupae. Eclosed males are arrested by sex pheromone that disseminates from female pupae even before adult females eclose. Communication in C. pomonella within and among developmental stages (larva-larva and pupa-adult, respectively) may be a strategy to procure mates. If so, our data add to current knowledge that attraction of mates in insects relies on communication among adults, or pupae and adults.

Adaptation, Physiological↗

PubMed2002

Where to find a mate? Resource-based sexual communication of webbing clothes moth.

Mate location in moths typically entails long-range attraction of males to female-produced pheromone. Here, we show that male and female webbing clothes moths, Tineola bisselliella, seek larval habitats (dry carrion, animal lairs, etc) to encounter mates. With males seeking, and arriving at, larval habitat earlier at night than females, male-produced pheromonal and sonic signals enhance the habitat's attractiveness to females. This resource-based mating strategy of T bisselliella differs from that known for most other moths. It may have evolved in response to larval habitats that are patchy and temporary, but that disseminate attractive semiochemicals so abundantly that T bisselliella encounter them more readily than their own pheromones.

Animal Communication↗

PubMed2002

2-Methyl-(Z)-7-octadecene: sex pheromone of allopatric Lymantria lucescens and L. serva.

Our objective was to identify the sex pheromone of Lymantria lucescens and Lymantria serva (Lepidoptera: Lymantriidae), whose larvae defoliate, respectively, Quercus spp. in temperate regions and Ficus spp. in the subtropics. Coupled gas chromatographic-electroantennographic (GC-EAD) detection analyses of pheromone gland extracts revealed one EAD active compound produced by female L. lucescens and by female L. serva. This was identified as 2-methyl-(Z)-7-octadecene (2me-Z7-18Hy) by retention index calculations on DB-5, DB-23, and DB-210 columns and by comparative GC-mass spectrometric (MS) and GC-EAD analyses of the insect-produced candidate pheromone and synthetic 2me-Z7-18Hy. In field experiments, traps baited with 2me-Z7-18Hy captured male L. lucescens near Toyota City, Japan, and male L. serva in Taipei, Taiwan. Allopatric distribution of L. lucescens and L. serva seems to allow both species to use the same sex pheromone without compromising its specificity.

Alkenes↗

PubMed2002

(Z,Z)-4,7-tridecadien-(S)-2-yl acetate: sex pheromone of Douglas-fir cone gall midge, Contarinia oregonensis.

Our objectives were to identify and field test the sex pheromone of female Douglas-fir cone gall midge, Contarinia oregonensis (Diptera: Ce-cidomyiidae). Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses of pheromone extract revealed a single compound (A) that elicited responses from male antennae. Hydrogenation of pheromone extract, followed by renewed GC-EAD analysis, revealed a new EAD-active compound with chromatographic characteristics identical to those of tridecan-2-yl acetate on five fused silica columns (DB-5, DB-210, DB-23, SP-1000, and Cyclodex-B). Syntheses, chromatography, and retention index calculations of all possible tridecen-2-yl acetates suggested that the candidate pheromone A was a tridecadien-2-yl acetate with nonconjugated double bonds. Synthetic candidate pheromone component (Z,Z)-4,7-tridecadien-2-yl acetate (Z4Z7) cochromatographed with A on all analytical columns and elicited comparable antennal activity. In GC-EAD analyses that separated the enantiomers (Z,Z)-4,7-tridecadien-(S)-2-yl acetate (2S-Z4Z7) and (Z,Z)-4,7-tridecadien-(R)-2-yl acetate (2R-Z4Z7) with baseline resolution, only 2S-Z4Z7 as a component in a racemic standard or in pheromone extract elicited antennal responses. In Douglas-fir seed orchards, sticky traps baited with 2S-Z4Z7 captured male C. oregonensis, whereas 2R-Z4Z7 was behaviorally benign. Comparable catches of males in traps baited with racemic Z4Z7 (50 microg) or virgin female C. oregonensis suggested that synthetic pheromone baits could be developed for monitoring C. oregonensis populations in commercial Douglas-fir seed orchards.

Acetates↗

PubMed2002

Incidence, symptoms, and intensity of damage by three coffee stem borers (Coleoptera: Cerambycidae) in South Yunan, China.

Sampling studies were conducted in coffee plantations in South Yunan to assess the incidence, symptoms, and intensity of damage by three stem borers: Xylotrechus quadripes (Chevrolat), Acalolepta cervina (Hope), and Bacchisa sp. near pallidiventris (Thomson). Of 5,690 plants sampled in eight plantations, 440 were infested with A. cervina, 63 with X. quadripes, and three with B. pallidiventris. Plants 5-7 yr old were 10 times more heavily infested with X. quadripes than 3- to 4-yr-old plants, whereas both age groups of plants had similar levels of infestation with A. cervina. Larval galleries of the three borer species markedly differ: A. cervina and B. pallidiventris larvae develop in subcortical galleries in the main stem (A. cervina) and lateral branches (B. pallidiventris), whereas larval galleries of X. quadripes intermittently punctuate and transverse the xylem of main stems or lateral branches. Significantly more plant tissue was damaged in stems infested with X. quadripes than in those infested with A. cervina or B. pallidiventris. Stems infested with A. cervina or B. pallidiventris generally had only one or a few pupation chambers, whereas stems infested with X. quadripes contained numerous chambers. Quantitative and qualitative data collected through this study provide farmers with diagnostic tools to determine which borer species infested coffee plants. Comparison of life history traits and intensity of damage for the three borer species indicates that X. quadripes is the most severe pest of coffee in Yunan, and suggests that populations of X. quadripes have the greatest potential to steadily increase with time.

Animals↗