Host gall size and oviposition success by the parasitoid Eurytoma gigantea

Abstract. 1. Eurytoma gigantea Walsh is a specialist parasitoid of the tephritid gallmaker Eurosta solidaginis (Fitch).
2. In the natural environment the incidence of parasitism by Eurytoma is greater in small galls than in large ones.
3. Laboratory experiments demonstrated that small galls are not more frequently discovered; however, oviposition attempts on small galls were more likely to be successful.
4. Eurytoma spends much time probing galls too big to penetrate; this leads to a decrease in foraging efficiency when many large galls are present.
5. The chance of successfully penetrating a gall depends on the thickness of the gall wall and the length of the parasitoid's ovipositor.
6. A simulation model was constructed which shows that a gallmak-er's chance of being parasitized depends on gall size, the number of parasitoids that discover the gall, and their ovipositor lengths.     

Diurnal Changes in Asparaginase Activity in Pea Leaves: II. REGULATION OF ACTIVITY

Pea leaf asparaginase is stabilized by asparagine and aspartateduring incubation. In crude extracts this effect was enhancedby products of the light reaction (NADPH, NADH, or reduced ferredoxin),but these compounds were ineffective on the purified enzyme,or in the absence of asparagine. MgATP, MgADP and oxidized ferredoxinreduced asparaginase activity in purified preparation reducedor oxidized glutathione had no effect. Asparaginase activitydoes not appear to be modulated via phosphorylation/dephosphorylation.The presence of calcium during extraction increased asparaginaseactivity more than 2-fold, but addition of calcium to extractsprepared in its absence had no effect; calmodulin had no effecton activity. Co-extraction of light- and dark-treated tissueshowed that soluble factors are not responsible for the diurnalvariation in asparaginase activity. Association of asparaginasewith membranes did not account for changes in extractable activity.Use of the protein synthesis inhibitors cycloheximide, puromycin,emetine, actinomycin D and cordycepin and the thiol proteaseinhibitor leupeptin suggested that mRNA and protein synthesisare required for the increase of asparaginase activity duringthe light period and that proteolytic degradation accounts forthe decrease during the dark. Key words: Pisum sativum, asparaginase, protein synthesis, proteolysis.     

Diurnal Changes in Asparaginase Activity in Pea Leaves: I. THE REQUIREMENT FOR LIGHT FOR INCREASED ACTIVITY

During the growth of leaves of Pisum sativum L., levels of asparaginase(E.C. 3.5.1.1 [EC] ) showed a diurnal variation during a 3 d periodof leaf expansion, increasing in the light and decreasing inthe dark period; the greatest diurnal variation being foundin half-expanded leaves. Asparaginase activity in half-expandedleaves reached a maximum after 4 h exposure to light and thisactivity was maintained over the rest of the light period. Changesin asparaginase activity were not influenced by diurnal temperaturechanges. The increase in asparaginase activity during the lightperiod was directly proportional to the photon flux densityover the range 0–285 µmol m^-2 s^-1 PAR. The increaseof asparaginase activity during illumination of detached leaveswas inhibited by the photosynthetic electron transport inhibitors3-(3', 4'-dichlorophenyl)-1, 1-dimethylurea (DCMU) and atrazine.These observations indicate that the increase in asparaginaseactivity in half-expanded leaves is dependent upon non-cyclicelectron transport. Key words: Pisum sativum, asparaginase, photosynthetic electron transport     

Research in Mammalian Mastication

Ongoing research efforts in mammalian mastication have definedseveral broad areas of mutual interest to workers in the discipline.They are (1) interrelationships between masticatory movements,(2) actions of the masticatory muscles, (3) comparisons betweenmasticatory structures and functions, (4) developmental aspects,(5) comparisons between limbs and jaws, and (6) neurophysiologicconsiderations. The roles (potential and actual) of masticatorycentral pattern generators, cerebral "mastication areas," differentneural mechanisms between mammalian taxa, neurophysiologic/morphologicinteractions, and biochemical factors within the total milieuof mammalian mastication are discussed.     

Temporal constancy in grasshopper assemblies (Orthoptera: Acrididae)

ABSTRACT.

• 1 Temporal constancy in the structure of grasshopper assemblies (about forty-five species each) from two types of North American grasslands was assessed; one site was followed 25 years and the other 7 years.
• 2 Densities and relative abundances varied but composition of assemblies based on ranks suggested significant structure when three or more species were included in the analysis.
• 3 Results compared favourably with other insect herbivore assemblies which have been examined; variability in population change was intermediate along the spectrum of organisms which have been studied.

     

Transformation-defective Strains of <Emphasis Type="Italic">Haemophilus influenzae</Emphasis>

THE mechanism of genetic transformation and recombination can be studied with mutants deficient in various stages of transformation and recombination, but their isolation has often proved to be difficult and time-consuming. We have developed a method for selectively removing cells which transform normally from cultures of Haemophilus influenzae. Mutants isolated from such cultures have been tested for DNA uptake, integration, ultraviolet and X-ray sensitivities and ultraviolet induced DNA synthesis delay.     

Redescription of Eimeria angusta Allen, 1934 and E. bonasae Allen, 1934 (Protozoa: Eimeriidae) from the Ruffed Grouse Bonasa umbellus1

SYNOPSIS Eimeria angusta Allen, 1934 and E. bonasae Allen, 1934 are redescribed from a ruffed grouse Bonasa umbellus. Oocysts of E. angusta were ellipsoidal to elongate ovoid, had micropyles and were 28-37 by 15-19 μ (mean 32.5 by 17.1 μ), with a length-width ratio of 1.67-2.19 (mean 1.91). Eimeria bonasae oocysts were spherical to subspherical and 18-25 by 18-23 μ (mean 21.6 by 20.6), with a length-width ratio of 1.00-1.16 (mean 1.05).