Host finding and discrimination in Diglyphus isaea,a parasitoid of the chrysanthemum leaf miner,Chromatomyia syngenesiae

Naive and experienced Diglyphus isaea were attracted by host plant odours of lettuce and chrysanthemum to search and probe on infested and uninfested leaves. A slight preference was shown for leaves infested with Chromatomyia syngenesiae. At close range, visual stimuli were unnecessary for oviposition and host‐feeding. Contact with uninfested lettuce and chrysanthemum elicited searching and probing behaviour whereas host frass did not. Host larval movement appeared to aid host detection at close range. The number of ovipositor probes increased with proximity to live hosts but not for stationary, dead hosts. Dead hosts were frequently walked over or missed when D. isaea passed within 0.5 cm of the stationary larvae. Dead hosts were also rejected for oviposition but not for host feeding. Both naive and experienced females discriminated between healthy hosts and those which had been attacked by conspecifics or encountered previously.     

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids

Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1, n = 16 in study 2), running (n = 16 in study 1 and n = 16 in study 2) and control (n = 17 in study 1 and n = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9-10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%-85% of the maximal oxygen consumption (VO2max) using portable heart rate metres and the mean heart rate was 156-157 beats.min-1 in the training groups. In the pooled data of the two studies the mean increase in the VO2max (in ml.min-1.kg-1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase in VO2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9-10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.     

Clonal diversity, population structure, and dispersal in the parthenogenetic moth Ectoedemia argyropeza

Populations of the parthenogenetic moth Ectoedemia argyropeza (Lepidoptera, Nepticulidae) were studied for their clonal composition. Clones were characterized by 6 polymorphic enzyme loci. In a geographic survey 32 clones were observed among 812 individuals. Two clones were predominant, together they explained over 75% of the total variation. Relationships among clones hinted at a monophyletic origin of the species. Analysis of the life cycle and population structure indicated that E. argyropeza is a very sedentary species, with bottlenecks, drift, and passive migration as important population genetical factors moulding the variation.     

Spring and summer hosts for Pieris rapae in Southern Spain with special attention to Capparis spinosa

The suitability of different host plants for Pieris rapae L. in the South of the Iberian Peninsula, was studied in relation to host plant phenology, female behaviour, and larval development. Capparis spinosa is the only host plant available during the dry season of the year in the area studied. D. virgata, R. raphanistrum, H. incana and S. alba being suitable spring hosts. Comparative studies on mortality, larval development and larval growth between C. spinosa and the spring hosts revealed no significant differences.

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Résumé L'adéquation de différentes plantes comme hôtes de P. rapae a été examinée en fonction de la phénologie des végétaux, du comportement de la femelle et du développement larvaire dans le sud de la péninsule ibérique. Pendant la saison sèche, C. spinosa est la seule plant convenable dans la zone étudiée. Diplotaxis virgata, Raphanus raphanistrum, Hirschfeldia incana et Sinapis alba sont des hôtes printaniers convenables. La mortalité, le développement et la croissance larvaires ne sont pas différentes sur C. spinosa et sur les hôtes de printemps.

     

Developmental rates of heterozygous and homozygous rainbow trout reared at three temperatures

The hatching distributions of rainbow trout (Salmo gairdneri) with different genotypes at eight loci are compared in two experiments with the same strain. Embryos were incubated at temperatures colder (5 and 8°C) and warmer (12°C) than normally experienced by these fish (9.5°C). At hatching, embryos were separated into five hatching groups representing the chronological order of hatching. There is no significant correlation between multilocus heterozygosity and hatching time at any temperature in either experiment. Fish in the middle of the hatching distribution had the highest average heterozygosity. In both experiments, heterozygotes at the majority of loci examined tended to hatch relatively later within the hatching distribution at 12°C than at both 5 and 8°C. Fish with different genotypes atPgm2 andCk1 showed significant differences in hatching time that were consistent between experiments.Ck1 heterozygotes hatched sooner than homozygotes at 8°C but later at 12°C.Pgm2 heterozygotes hatched later than homozygotes at all temperatures and significantly later in four of five cases. At the other loci examined, however, the relative hatching distributions of fish with particular genotypes were not significantly different or repeatable between experiments.This research was supported by National Science Foundation Grant BSR-8300039 awarded to Dr. Fred W. Allendorf. Moira M. Ferguson was supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada.     

Biology of Subanguina picridis,a Potential Biological Control Agent of Russian Knapweed

The knapweed nematode, Subanguina picridis, forms galls on the leaves, stems, and root collar of Russian knapweed, Acroptilon repens. After being revived from a dormant, cryptobiotic state, second-stage juveniles required at least 1 month in a free-living state before becoming infective. Galls were induced on relatively slow-growing host plants that retained their apical meristems at or near the soil surface for 2-5 weeks. Galls developed extensive areas of nutritive tissue. The nematode was introduced from the Soviet Union and released in Canada for the biological control of Russian knapweed.     

THE HOST RANGE OF THE CHLORELLAVOROUS BACTERIUM ("VAMPIROVIBRIO CHLORELLVORUS")

The chlorellavorous bacterium . "Vampirovibrio chlorellavorus" Gromov et Mamkaeva, grows only by killing and consuming the cell contents of species of the green alga Chlorella Beijerinck. Of the 76 algal strains examined in this study, the bacterium attacks all 31 strains of the species C. vulgaris. C. sorokiniana, and C. kessleri, but attacks only two of 39 strains of nine other Chlorella species. Neither of two Prototheca strains was susceptible to attack. This narrow host specificity may be related to cell surface properties .     

Relative Virulence of Meloidogyne incognita Host Races on Soybean

Sensitivity and host efficiency of susceptible (''Lee 68'', ''Coker 156'') and resistant (''Bragg'', ''Centennial'', ''Forrest'', ''Lee 74'') soybean (Glycine max (L.) Merr.) cultivars for races of Meloidogyne incognita (Mi) were determined in greenhouse experiments. Eight Mi populations collected from the southeastern United States were utilized. All Mi races reproduced readily on Lee 68 and Lee 74 and moderately on Forrest and Bragg. Coker 156 exhibited resistance to races 1 and 2, and some race 3 populations, but was very susceptible to certain race 3 and 4 populations. Reproduction of all races was lowest on Centennial. Forrest and Centennial shoot growth was not significantly suppressed by any race. There were no distinct differences in virulence between races except for a race 3 population which reproduced readily on all cultivars, stunting their growth. Considerable variation in reproduction existed within races 1 and 3.