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.     

Small rodents and other mammals associated with mountain meadows as reservoirs of Giardia spp. and Campylobacter spp.

Sixty-five percent (469 of 722) of the fecal samples collected from small rodents in the central Washington Cascade mountains were positive for Giardia spp. Trapping studies showed that microtines of the genus Microtus were heavily infected with the parasite. Morphologically the cysts and trophozoites were of the Giardia duodenalis type. Small-rodent populations appear to maintain their infection throughout the year. Our data suggest that there is no difference in the percentage of positive animals in areas receiving a lot of human use as opposed to animals in those areas receiving very little or no human use. Giardia spp. were also found in elk and beaver fecal samples. Campylobacter spp. were recovered infrequently from the small rodents inhabiting alpine meadows. Of 551 specimens cultured, less than 1% were positive for the bacterium, and the isolates were identified as Campylobacter coli. Water voles were susceptible to a human isolate of Campylobacter jejuni and shed the bacterium for several weeks. C. jejuni was also isolated from a bear fecal sample collected from a protected watershed. Our studies indicate that microtines and possibly other small rodents inhabiting mountain meadows have a potential to act as a reservoir for both Giardia spp. and Campylobacter spp. Because these animals may carry human pathogens, they should be included in animal surveys designed to assess the health risks associated with mountain watersheds.     

Reduced tumour necrosis factor-induced cytotoxicity by inhibitors of the arachidonic acid metabolism

The mechanism of tumour necrosis factor-mediated cytotoxicity was investigated by using various inhibitors of arachidonic acid metabolism. Phospholipase A2 inhibitors with different modes of action interfered with the cytotoxic action of TNF, whereas phospholipase C inhibitors did not. Neither cyclooxygenase nor lipoxygenase-blockers had a significant effect on TNF action. Experiments with scavengers of toxic oxygen radicals gave ambiguous results. The data obtained suggest the involvement of phospholipase A2 and arachidonic acid in the cytotoxic mechanism of TNF, but the exact role of these molecules is, however, still to be determined.     

A toxin fromPasteurella multocida serogroup D enhances swine herpesvirus 1 replication/lethality in vitro and in vivo

In swine, the nasal turbinate epithelium is both a site of swine herpesvirus 1 (pseudorabies virus, PRV) replication and a tissue affected by toxin fromPasteurella multocida serogroup D. We examined the effects of exposure to PRV and exposure to toxin in mice, swine, and nasal turbinate cell cultures. Increased mortality in mice was observed when nonlethal doses of PRV (1000 or 100 plaque-forming units, PFU) were administered along with nonlethal doses (60–200 ng/kg) of toxin. In swine, clinical disease and death in adult pigs was observed after an intradermal injection of toxin (20 ng/kg) and intranasal exposure to 1000 PFU/kg of PRV. Nasal turbinate cell cultures incubated with toxin and PRV had increased protein synthesis, DNA synthesis, and increased recovery of virus particles. These findings indicate that a toxin fromP. multocida serogroup D enhances swine herpesvirus 1 replication and lethality in cell cultures and animal models.     

The response of murine intestinal crypts to short-range promethium-147 beta irradiation: deductions concerning clonogenic cell numbers and positions

An exteriorized loop of mouse intestine was exposed to 147Pm low-energy electrons, where the dose rate decreased by a factor of 5 from the base of the crypt to the top of the proliferative zone. A crypt survival curve was obtained, expressed in terms of exposure time. The shape of the curve was interpreted in terms of survival parameters for colony-forming cells (clonogens) derived using 137Cs gamma rays and the depth-dose curve measured for 147Pm electrons. It is concluded that the shape of the crypt survival curve using 147Pm electrons is inconsistent with the notion of either the presence of a large number of clonogens or a small number near the top of the proliferative zone. A computer fitting procedure showed that the best agreement between predicted and observed curves was achieved with 2.7 +/- 0.5 clonogens at cell position 5.6 +/- 0.6, in the putative stem-cell zone.     

A class of linear spectral models and analyses for the study of longitudinal data

Longitudinal data can always be represented by a time series with a deterministic trend and randomly correlated residuals, the latter of which do not usually form a stationary process. The class of linear spectral models is a basis for the exploratory analysis of these data. The theory and techniques of factor analysis provide a means by which one component of the residual series can be separated from an error series, and then partitioned into a sum of randomly scaled metameters that characterize the sample paths of the residuals. These metameters, together with linear modelling techniques, are then used to partition the nonrandom trend into a determined component, which is associated with the sample paths of the residuals, and an independent inherent component. Linear spectral models are assumption-free and represent both random and nonrandom trends with fewer terms than any other mixed-effects linear model. Data on body-weight growth of juvenile mice are used in this paper to illustrate the application of linear spectral models, through a relatively sophisticated exploratory analysis.