Characterisation and serological relationships of strains of Kashmir bee virus

Isolates of novel strains of Kashmir bee virus (KBV) were obtained from field-collected dead adults of Apis mellifera from honey bee colonies in Canada and Spain. They differed from other strains of KBV in their tendency to aggregate in dilute buffer solution and in containing only three proteins when analysed by SDS-polyacrylamide gel electrophoresis compared with five proteins resolved in the type strain of KBV from Apis cerana in India and six proteins in KBV strains from South Australia and New Zealand. Immunodiffusion tests and Western blotting studies indicated that the five virus isolates were serologically related and all were related to acute paralysis virus (APV). The world distribution of KBV strains and their apparent relationship with APV are discussed.     

Effects of seed size, planting density and planting pattern on the severity of silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) diseases of potatoes

The effects of different seed sizes, planting densities and planting patterns on the transmission of silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) diseases of potatoes were examined in five field experiments with cv. Estima in 1991–93.
In all experiments, silver scurf was more severe with increase in seed size and planting density. At high planting density, silver scurf was less severe from a square planting pattern than from planting in wide rows. The incidence of black scurf also tended to increase with increase in seed size and was increased markedly high planting density.     

The calling behaviour and spatial distribution of male bushcrickets (Sciarasaga quadrata) and their relationship to parasitism by acoustically orienting tachinid flies

Abstract.

• 1 This paper examines the calling behaviour and spatial distribution of male Sciarasaga quadrata Rentz (Orthoptera: Tettigoniidae), a bushcricket that is subject to attack by an acoustically orienting parasitoid fly, Homotrixa sp. (Diptera: Tachinidae: Ormiini).
• 2 Checks on calling activity in populations of S.quadrata confirmed that calling began 2–3 h before sunset and continued well beyond midnight. Calling activity was not restricted by temperature with males calling over air temperatures of 10.6–24.2°C.
• 3 Nearest-neighbour analyses, within the sampled areas, revealed that the spacing between calling males was random and the minimum distance between calling males was 3.74 m. Mean distances between calling males varied between 9.2 m and 23.0 m and significantly changed as male density, which peaked at 0.36 calling males per 100 m², declined over the calling season.
• 4 Males showed no preference for any one plant species, with their distribution across bushes not significantly different to the frequency of the plants within the habitat. The perch height of calling males was on average half way up the height of a bush and was significantly influenced by the height of the bush. Perch height was not significantly influenced by proximity to calling males or by whether or not males were parasitized.
• 5 Site fidelity of males was low with only 0–10% of bushes occupied by calling males over successive nights. Males, though flightless, moved on average 6.70 m and up to 26.56 m per night.
• 6 No evidence was found for the use of aggregation in S.quadrata as a primary defence against ormiine attack. Commencing calling prior to sunset, frequent movement, and a lack of association with any particular plant species, although possibly relevant to ormiine attack, could also be explained in terms of other activities such as male-male interactions and mating behaviour.

     

Effect of Acetate on Esterase C Activity During the Growth Cycle of Paramecium*

SYNOPSIS Enhanced esterase C activity could be demonstrated by starch gel electrophoresis in various stocks of Paramecium spp. (P. primaurelia stocks 90 and 540, P. biaurelia stock 93, P. tetraurelia stock 29. P. pentaurelia stock 87, P. octaurelia stocks 31 and 300, and P. multimicronucleatum species 3, stock 8 MO) grown in Adaptation Medium. This esterase, however, was barely detectable when they were cultivated in Axenic Medium. Addition of trypticase to Adaptation Medium resulted in reduction of esterase C in the ciliates. This effect is ascribable to Na acetate present in trypticase. Since esterase C increased with the decrease in acetate concentration (as estimated by gas-liquid chromatography) during growth of Paramecium, acetate appears to be utilized by the cells. Sensitivity of esterase C to acetate occurs in all 6 species of Paramecium examined. Different stocks within a species may have different levels of sensitivity; in one case this is genetically determined. The results emphasize the importance of controlling and manipulating growth conditions for the assessment of inter- and intraspecies variations in the isozymes of Paramecium.     

Interspecies Relationships in the Paramecium aurelia Complex: Acid Phosphatase Variation1

ABSTRACT. Up to five zones of acid phosphatase activity appear in gels after electrophoresis of detergent-treated extracts from 13 of the 14 species of the Paramecium aurelia complex. The overall pattern is somewhat similar for all species: differences in intensity and mobility of individual zones permit the grouping of these sibling species into eight groups. All 14 species can be identified using the procedure of enzyme electrophoresis, although two of them are more similar than is usually the case. Problems of misclassification are discussed in terms of the nature and frequency of variants. With the judicious choice of enzymes used to screen new stocks, these problems can be circumvented. Species relationships are updated using 11 enzymes. A dendrogram constructed from the matrix of genetic distances shows four clusters of species: (i) P. biaurelia, P. triaurelia; (ii) P. primaurelia, P. pentaurelia, P. sexaurelia, P. novaurelia; (iii) P. septaurelia, P. undecaurelia, P. tredecaurelia, P. quadecaurelia; and (iv) P. tetraurelia, P. octaurelia, P. decaurelia, P. dodecaurelia. Distances between the species are large, on the order of the differences between Drosophila species. The species are characterized by an extraordinary lack of geographical differentiation and great morphological similarity, which contrasts strongly with the molecular differentiation.     

The Correlation of Digestive Vacuole pH and Size with the Digestive Cycle in Paramecium caudatum1

ABSTRACT. The temporal changes in the size and pH of digestive vacuoles (DV) in Paramecium caudatum were reevaluated. Cells were pulsed briefly with polystyrene latex spheres or heat-killed yeast stained with three sulfonphthalein indicator dyes. Within 5 min of formation the intravacuolar pH declined from ～7 to 3. With the exception of a transient and early increase in vacuolar size, vacuole condensation occurred rapidly and paralleled the acidification so that vacuoles reached their lowest pH and minimal size simultaneously. Neutralization and expansion of vacuole size began when vacuoles were GT8 min old. No labeled vacuoles were defecated prior to 21 min after formation but almost all DV were defecated within 1 h so that the digestive cycle of individual vacuoles ranged from 21 to 60 min. Based on these size and pH changes, the presence of acid phosphatase activity, and membrane morphology, digestive vacuoles can be grouped into four stages of digestion. The DV-I are GT6 min old and undergo rapid condensation and acidification. The DV-II are between 4 to 10 min old and are the most condensed and acidic vacuoles. The DV-III range in age from 8 to ～20 min and include the expanding or expanded vacuoles that result from lysosomes fusing with DV-II. The DV-IV are GD21 min old, and since digestion is presumably completed, they can be defecated. The rise in intravacuolar pH that accompanies vacuole expansion suggests that lysosomes play a role in vacuole neutralization in addition to their degradative functions. The acidification and condensation processes in DV-I appear to be unrelated to lysosomal function, as no acid phosphaiase activity has been detected at this stage, but may be related to phagosomal functions important in killing food organisms, denaturing proteins prior to digestion, and preparing vacuole membrane for fusion with lysosomes.     

Biochemical Aspects of Lipid Storage and Utilization in Animals

The high energy content of lipids makes these compounds attractiveto active metazoans as alight form of fuel storage. Animalshave evolved complex systems of enzymes and transport proteinsin order to utilize lipids for the generation of energy. Whilethe enzymatic systems responsible for lipid synthesis and oxidationare probably similar in all metazoans, mechanisms for controlof the rates of these processes differ with taxonomic group.The means by which lipids are transported through the body fluidsof metazoans also show phylogenetic variation. Complete, quantitativedata on the mechanisms and rates of lipid digestion, synthesis,transport and utilization are available for only a very fewmammals, birds and insects. This would seem to be a very fertilefield for comparative physiologists.