Do pollen beetles need pollen? The effect of pollen on oviposition,survival, and development of a flower‐feeding herbivore

Abstract.  1. Pollen is considered to be an important dietary component for many species of flower-feeding herbivores. Its influence on oviposition site selection by the pollen beetle Meligethes aeneus , and on the development of its larvae was investigated.
2. The effects of pollen presence and absence on adult, egg, and larval incidence in the field, and on larval development in the laboratory were compared through the use of Synergy, a composite hybrid oilseed rape Brassica napus variety comprising male-fertile (with pollen) and male-sterile (without pollen) plants.
3. In the field, adult females were more abundant on male-fertile plants during flowering, and a greater proportion of male-fertile than male-sterile buds were accepted for oviposition. These data indicate a possible role of pollen in oviposition site selection by female pollen beetles.
4. The numbers of first instar larvae on the two plant lines did not differ; however, more second instars were found on male-fertile than on male-sterile flowers. This suggests a greater larval survival on male-fertile plants, possibly due to the more readily available food resources and better nutrition afforded by the presence of pollen.
5. Laboratory experiments confirmed that a diet which included pollen improved survival to adulthood and resulted in heavier pupae and adults; however, pollen was not obligatory for larval survival and development.
6. The pollen beetle, previously thought to be an obligate pollen feeder, is therefore more generalist in its requirements for development. These findings may relate to the nutritional and behavioural ecology of other flower-feeding herbivores.     

Purine Ribonucleosidase g from Aspergillus foetidus

Nucleosidase g was prepared by growing Aspergillus foetidus on bran, and was purified by passage through a diethylaminoethyl-Sephadex column. The enzyme acted on the purine ribosides (except xanthosine) and on their 5'-phosphates. Action on the latter was a good means for preparing ribose-5-phosphate.     

Cloning of the mgtE Mg2+ transporter from Providencia stuartii and the distribution of mgtE in gram-negative and gram-positive bacteria.

The MM281 strain of Salmonella typhimurium possesses mutations in each of its three Mg2+ transport systems, requires 100 mM Mg2+ for growth, and was used to screen a genomic library from the gram-negative bacterium Providencia stuartii for clones that could restore the ability to grow without Mg2+ supplementation. The clones obtained also conferred sensitivity to Co2+, a phenotype similar to that seen with the S. typhimurium corA Mg2+ transport gene. The sequence of the cloned P. stuartii DNA revealed the presence of a single open reading frame, which was shown to express a protein with a gel molecular mass of 37 kDa in agreement with the deduced size of 34 kDa. Despite a phenotype similar to that of corA and the close phylogenetic relationship between P. stuartii and S. typhimurium, this new putative Mg2+ transporter lacks similarity to the CorA Mg2+ transporter and is instead homologous to MgtE, a newly discovered Mg2+ transport protein from the gram-positive bacterium Bacillus firmus OF4. The distribution of mgtE in bacteria was studied by Southern blot hybridization to PCR amplification products. In contrast to the ubiquity of the corA gene, which encodes the dominant constitutive Mg2+ influx system of bacteria, mgtE has a much more limited phylogenetic distribution.     

Homologous chromosome pairing.

Commonly accepted precepts are challenged: (1) that homologous chromosome pairing is normally mediated by nuclear envelope attachment sites; (2) that crossover site establishment awaits synaptic completion; and (3) that it is the function of the synaptonemal complex to hold homologues in register so that equal crossing over can occur, and perhaps to provide machinery for the crossover process. Although these views may eventually be shown to be true, it is felt that currently available evidence does not warrant their full acceptance, and that alternatives should be considered. As examples of alternatives the following ideas, with some supporting evidence, are suggested: (1) homologous chromosome pairing (in non-haplont organisms) may be accomplished by chance meeting of homologue segments (followed by establishment of invisible, elastic connectors) at congression for a mitotic metaphase (in many cases perhaps the premeiotic mitosis); (2) crossover sites may be established before, during, or immediately following initiation of synapsis; and (3) the synaptonemal complex may somehow function in the crossover process at the inception of its formation, but its complete deployment throughout each normal bivalent may serve some other role, such as mediation of the binding of sister chromatids apparently required for chiasma maintenance until anaphase I.     

Cohesive sediment transport: emerging issues for toxic chemical management

The association of many environmentally sensitive chemicals and their transformation products with mineral and organic substrates is of considerable importance for environmental monitoring, prediction and management purposes in rivers and their basins. Our understanding of these relationships is poor. This paper reviews processes of particular concern, including the physical behaviour of fine-grained (< 63 µm) sediment in freshwater; the role of flocculation as a transport vector; the processes that control freshwater flocculation including microbiological factors; the uncertainty in conventional sediment transport models for predicting pathways of sediment-associated chemistry; the relationship between suspended sediment and toxicity in the water column; and the partitioning of chemicals between the sediment, organic and water phase, including the significance of these in predicting chemical transport on suspended matter.     

Effect of counselling on the psychiatric morbidity associated with mastectomy.

A controlled trial was conducted to determine whether counselling by a specialist nurse prevented the psychiatric morbidity associated with mastectomy and breast cancer. Seventy-five patients were counselled by the nurse and monitored during follow-up, while 77 patients received only the care normally given by the surgical unit. Counselling failed to prevent morbidity, but the nurse''s regular monitoring of the women''s progress led her to recognise and refer 76% of those who needed psychiatric help. Only 15% of the control group whose condition warranted help were recognised and referred. Consequently, 12 to 18 months after mastectomy there was much less psychiatric morbidity in the counselled group (12%) than in the control group (39%). These findings highlight the high degree of psychiatric morbidity in patients who have undergone mastectomy and indicate the need to find ways of reducing this morbidity.     

EPR spectra of photosystem I and other iron protein components in intact cells of cyanobacteria.

Electron paramagnetic resonance (EPR) spectra were recorded of whole filaments of the cyanobacteria Nostoc muscorum and Anabaena cylindrica. Signals due to manganese were removed by freezing and thawing the cells in EDTA. EPR spectra were assigned on the basis of their g values, linewidths, temperature dependence and response to dithionite and light treatments. The principal components identified were: (i) rhombic Fe3+ (signal at g = 4.3), probably a soluble storage form of iron; (ii) iron-sulfur centers A and B of Photosystem I; (iii) the photochemical electron acceptor 'X' of Photosystem I; this component was also observed for the first time in isolated heterocysts; (iv) soluble ferredoxin which was present at a concentration of 1 molecule per 140 +/- 20 chlorophyll molecules; (v) a membrane-bound iron-sulfur protein (g = 1.92). A signal g = 6 in the oxidized state was probably due to an unidentified heme compound. During deprivation of iron the rhombic Fe3+, centers A, B and X of Photosystem I, and soluble ferredoxin were all observed to decrease.     

Direct cytological evidence for true terminalization of chiasmata in maize

Equational and disjunctional separation of heterozygous heterochromatic regions was observed relative to chiasma positions at diakinesis. Equational separation of heterozygous knobs was frequently observed and always accompanied by a chiasma distal to the knob. This is considered evidence that in these cases a crossover had occurred in a position proximal to the knob and had terminalized to a position distal to the knob by the time of fixation for observation.     

Pulmonary metabolism of epoxides.

Activities of epoxide hydrase (EH) and glutathione S-transferase (GST) have been measured in pulmonary tissue from several species. On the basis of total organ activity, pulmonary tissue has less capacity than liver tissue to metabolize epoxides. Pulmonary EH and GST appear to be refractory to induction by typical agents. Rat pulmonary GST will conjugate a variety of epoxides, but K-region epoxides are metabolized at lower rates than alkene oxides. In the isolated perfused rabbit lung, benzo (a) pyrene-4,5-oxide (BPO) is metabolized by EH and GST at similar initial rates, but EH activity is lost after a few minutes, apparently owing to inadequate local substrate levels. GST from rabbit lung cytosol has been separated by chromatographic methods into six peaks of enzymic activity (toward 1-chloro-2,4-denitrobenzene). Of these peaks, all six metabolized BPO and two metabolized styrene oxide. Although EH and GST are less active in lung than in liver, pulmonary metabolism of epoxides is important because this tissue must be able to protect itself from arene oxides generated by pulmonary oxidative metabolism of polycyclic aromatic hydrocarbons.