RESUMEN

Relationships between Se and Hg in erythrocytes, and between these indices and intakes of fish and other foods, were studied as an adjunct to the British National Diet and Nutrition Survey (NDNS) of young people aged 4-18 years. Hg was measured in 965 packed erythrocyte samples by inductively coupled plasma mass spectrometry. Fe measurements permitted the calculation of whole-blood Hg. Erythrocyte and plasma Se, and 7 d weighed dietary intake estimates, were available. Erythrocyte Hg was positively skewed, normalised by log-transformation. It was 20 % higher in girls than boys (3.17 v. 2.65 nmol/l, P=0.004), and increased with age in boys but not girls. It was directly and strongly correlated with erythrocyte or plasma Se. Hg and Se concentrations were directly correlated with fish intake. Certain other food groups were also directly correlated with Se and Hg concentrations, but less strongly than for fish. The strength and consistency of the relationship between erythrocyte Hg and Se suggests an important chemical link. Previous studies suggest that Se protects against the toxicity of Hg, and that fish is an important source of both. No toxic levels of Hg were found, which is reassuring because of the known health benefits of fish consumption, especially oily fish. Hg intakes need to be monitored, especially in women of child-bearing age, to ensure that Food Standards Agency guidelines are met.

Asunto(s)

RESUMEN

Olfactory-mediated behavioral interactions were investigated among the five scolytid species comprising the southern pine bark beetle group. Behavioral response, as determined from field trap catch data, showed that each species was attracted in greatest numbers to the pheromonal blend produced by conspecifies. Interspecifically,D. frontalis displayed no cross-attractancy toIps pheromonal blends, but was weakly attracted to the pheromonal blend of femaleD. terebrans. ThreeIps species displayed varying degrees of cross-attraction as well as to theDendroctonus pheromonal blends. More specifically,I. calligraphus was attracted toI. avulsus and, to a very limited extent, also to the maleD. terebrans pheromonal blend.I. avulsus was somewhat more cross-attractive thanI. calligraphus and showed attraction to the pheromonal blends of femaleD. frontalis, male and femaleD. terebrans, maleI. calligraphus, and maleI. grandicollis. I. grandicollis showed the greatest degree of cross-attraction, particularly in response to theDendroctonus pheromonal blends.

RESUMEN

Observations and reports on the common furniture beetleAnobium punctatum suggested that, on emergence, females use a sex pheromone to attract males. GLC analysis of ovipositor extracts showed the presence of a single component, which was found to be active by EAG and coupled GLC-EAG techniques, and to attract males in both walking and flying assays. The pheromone was identified by GC-MS as 2,3-dihydro-2,3,5-trimethyl-6-(1-methyl-2-oxobutyl)-4H-pyran-4-one (stegobinone), which is the sex pheromone of another anobiid, the drugstore beetle,Stegobium paniceum. MaleA. punctatum responded equally to ovipositor extracts of either species, at both the sensory (EAG) and behavioral levels, which poses the question as to how species specificity in mate attraction is achieved.

Asunto(s)

RESUMEN

Abdominal coremata in male Estigmene acrea (Lepidoptera: Arctiidae) are inflated and displayed in aggregations to which females and males are attracted and where mating occurs (leks). Female E. acrea also release a sex pheromone which attracts males. These two mating behaviors occur in the same populations at different peak times on the same nights. Thus male lek formation and female calling occur in the same species, and the male coremata, or related structures, appear to be integrally associated with lek behavior.

RESUMEN

Two experiments were conducted to investigate the use of a pheromone-based trap-out technique for suppressing populations ofScolytus multistriatus. In the first experiment, elm bolts containing the immature stages ofS. multistriatus were placed in an isolated community that contained elm trees, but which was essentially devoid of a resident beetle population. The infested bolts produced a total of 46,485 adult beetles of which 20% were recovered on traps baited with synthetic pheromone. In the second experiment beetles were released in a desert valley containing no resident elms or beetles. Only 1% of 20,000 released beetles were recaptured on traps erected on vertical cardboard cylinders and on elm logs. These rates of recapture are related to the attraction of beetles to naturally occurring brood sources versus pheromone-baited traps.

RESUMEN

Standing loblolly pines in southeastern North America are colonized by four sympatric species of bark beetles: Dendroctonus frontalis (Zimm.), Ips calligraphus (Germ.), I. grandicollis (Eichh.) and I. avulsus (Eichh.). The beetles compete for the limited amount of phloem tissue used as a site for reproduction. Using indices of niche breadth and niche overlap determined from the surface areas attacked, the interaction of colonizing beetle species in partitioning resources in entire trees and within each sample level was examined. The broadest niche breadth was exhibited by I. avulsus, while I. grandicollis had the narrowest. D. frontalis dominated the lower bole and overlapped primarily with I. calligraphus. The upper bole was similarly dominated by I. avulsus, which overlapped only slightly with D. frontalis, but overlapped extensively with I. calligraphus. Within tree species diversity was highest in the mid-bole sections and declined progressively toward the stump and top. Increasing species diversity showed a strong positive correlation with increasing mean niche overlap.

RESUMEN

The following three aspects of the biology of the marine insect Halobates robustus were studied, during a two week observation period, at several sites in the Galapagos Islands: distribution, aggregation behaviour and rhythmicity of locomotory activity. H. robustus occurred in highest numbers on the water surface at shores fringed with mangroves. The aggregations of H. robustus varied according to their location and density. Copulating adults formed dense, floating aggregations, which tended to be close to rocks or mangroves. Late instar nymphs were less aggregated and, in lagoons (where there was some shelter from direct tidal forces), were furthest from the shore. In two types of habitat (mangrove-fringed, sandy shores and rocky shores) the aggregations of H. robustus showed a pronounced ability to maintain a floating station in relation to the surrounding environment, irrespective of tidal movements (in one case at 34 m from the nearest fixed objects). Evidence of the ability of the aggregations to maintain station on the water surface was also obtained by comparing the movements of H. robustus with those of floating polystyrene particles, which move passively with wind and tide. Laboratory observations and experiments indicated no clear periodicity in locomotory movements throughout a 24 h period. However, the frequency of encounters between individuals showed two daily peaks, post-dawn and pre-dusk, with fewer encounters during the day and only occasional encounters during the night. By shifting the light-dark cycle it was demonstrated that the daily bimodal rhythm of encounters is triggered by dawn and, since it is not maintained in constant light or dark, an 'hour-glass' mechanism is suggested. The contributions of single adults, of copulating pairs and of immature stages to the overall pattern of activity were also determined. Immature stages did not affect the overall rate of encounters significantly and the interactions between single and copulating pairs of adults appear to have been responsible for the bimodal pattern.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)