Liebman,M., Mohler,C.L., and Staver,C.P. Ecological management of agricultural weeds

According to the publisher’s jacket note, ‘If youare considering a career in research . . . this bookshould offer some advice’. I find no reason to argue withthis claim. Nancy Rothwell has provided a thorough treatmentof the stages and progression of     

Development of Caryospora simplex (Apicomplexa: Eimeriidae) from Sporozoites to Oocysts in Human Embryonic Lung Cell Culture1

Leighton tubes containing monolayers of human embryonic lung cells were inoculated with 70,000 or 30,000 sporozoites of the viperid coccidium Caryospora simplex and examined at 1, 2, 4, 6, 8, 10, 12, 14, 16, and 18 days post-inoculation (PI). By day 1 PI, sporozoites had penetrated cells and were within parasitophorous vacuoles. Most sporozoites became spherical and then underwent karyokinesis several times between days 2 and 6 PI. Mature Type I meronts were found on days 6–16 PI and contained 8 to 22 short, stout merozoites. Mature Type II meronts were present on days 10–18 PI and contained 8 to 22 long, slender merozoites. Developing gamonts (undifferentiated sexual stages) were observed on days 14 and 16 PI. Mature micro- and macrogametes and thin-walled unsporulated oocysts were present on days 16 and 18 PI. Attempts to sporulate oocysts in tissue culture medium or in a 2.5% (w/v) aqueous solution of K₂Cr₂O₇ at 25/°C and 37°C were unsuccessful; only a few oocysts developed to the contracted sporont stage. Four Swiss-Webster mice injected intraperitoneally with merozoites obtained from Leighton tubes on day 10 PI did not acquire infections. This is the second coccidium reported to complete its entire development, from sporozoite to oocyst, in cell culture.     

Ultrastructural Observations on Renal Schizogony of Leucocytozoon dubreuili in the American Robin

SYNOPSIS. The schizogonic development of Leucocytozoon dubreuili in the kidney proximal tubule cells of the American robin, Turdus migratorius , was studied by electron microscopy. Renal schizogony is initiated by the entry of certain hepatic merozoites into cells of the proximal tubules. Development of the schizont consists of a coordinated sequence of events including extensive mitotic nuclear division, multiplication of mitochondria, increase in endoplasmic reticulum and ribosomes, differentiation of membranes, microtubules, micronemes and rhoptries, and cytoplasmic segmentation (cytomere formation). Merozoites form by budding around numerous centers in the schizont and, when mature, are bounded by a single plasma membrane subtended by microtubules. Each merozoite contains a large nucleus, a mitochondrion, and a well developed apical complex consisting of 3 polar rings, paired rhoptries, and numerous micronemes.
An atypical nuclear division observed in some maturing schizonts was characterized by the multiple fission of a nucleus within a persistent outer nuclear membrane and the absence of mitotic spindle apparatus. Alterations in infected renal cells consisted of disorganization and loss of cytoplasmic organelles and the accumulation of lipofuscin-like inclusions.     

Relationships between host blood factors and proteases in Glossina morsitans subspecies infected with Trypanosoma congolense

Abstract. Host blood effects on Trypanosoma congolense establishment in Glossina morsitans morsitans and Glossina morsitans centralis were investigated using goat, rabbit, cow and rhinoceros blood. Meals containing goat erythrocytes facilitated infection in G. m. morsitans , whereas meals containing goat plasma facilitated infection in G. m. centralis. Goat blood effects were not observed in the presence of complementary rabbit blood components. N-acetyl-glucosamine (a midguMectin inhibitor) increased infection rates in some, but not all, blood manipulations. Cholesterol increased infection rates in G. m. centralis only. Both compounds together added to cow blood produced superinfection in G. m. centralis , but not in G. m. morsitans. Midgut protease levels did not differ 6 days post-infection in flies maintaining infections versus flies clearing infections. Protease levels were weakly correlated with patterns of infection, but only in G. m. morsitans. These results suggest that physiological mechanisms responsible for variation in infection rates are only superficially similar in these closely-related tsetse.     

Geographic parthenogenesis and the common tea‐tree stick insect of New Zealand

Worldwide, parthenogenetic reproduction has evolved many times in the stick insects (Phasmatidae). Many parthenogenetic stick insects show the distribution pattern known as geographic parthenogenesis, in that they occupy habitats that are at higher altitude or latitude compared with their sexual relatives. Although it is often assumed that, in the short term, parthenogenetic populations will have a reproductive advantage over sexual populations; this is not necessarily the case. We present data on the distribution and evolutionary relationships of sexual and asexual populations of the New Zealand stick insect, Clitarchus hookeri. Males are common in the northern half of the species’ range but rare or absent elsewhere, and we found that most C. hookeri from putative‐parthenogenetic populations share a common ancestor. Female stick insects from bisexual populations of Clitarchus hookeri are capable of parthenogenetic reproduction, but those insects from putative‐parthenogenetic populations produced few offspring via sexual reproduction when males were available. We found similar fertility (hatching success) in mated and virgin females. Mated females produce equal numbers of male and female offspring, with most hatching about 9–16 weeks after laying. In contrast, most eggs from unmated females took longer to hatch (21–23 weeks), and most offspring were female. It appears that all C. hookeri females are capable of parthenogenetic reproduction, and thus could benefit from the numerical advantage this yields. Nevertheless, our phylogeographic evidence shows that the majority of all‐female populations over a wide geographic area originate from a single loss of sexual reproduction.     

A field trial to assess the effects of rabbit grazing on spring barley

Spring barley is widely grown throughout the UK and significant yield loss can occur as a result of rabbit grazing. In a 3-yr trial, spring barley was grown in six enclosures following current agronomic procedures and was subjected to grazing by different population densities of rabbits. The annual yield loss at the end of the trial was 0.5% rabbit⁻¹ ha⁻¹. The yield loss per rabbit was calculated to be around 25 kg and the financial loss was calculated as £2.00 per rabbit at 1998 prices (approx. £80 tonne⁻¹). Models allowing farmers to predict the levels and costs of damage by rabbits to winter wheat and for silage have already been developed. The results from this trial enable farmers to extend their predictions to include spring barley. The implications for this are discussed.     

Statistical power analysis of a 2-year field study and design of experiments to evaluate non-target effects of genetically modified Bacillius thuringiensis corn

Abstract 1. A 2‐year field study was conducted in 2000 and 2001 at a farm in Monmouth, Illinois to evaluate the effect of MON 863, a transgenic corn event that expresses the Cry3Bb1 protein for control of corn rootworms, on diverse groups of arthropod populations in a corn ecosystem. 2. The field study employed a split‐plot design with MON 863 and conventional corn as the main plots and several insecticide treatments as subplots; each main plot was replicated four times (i.e. n = 4 block replications for each corn variety). A large number of arthropod taxa were trapped, taxonomically characterised, and counted in all plots. A mixed linear repeated‐measures model was used for analysis of each taxon collected to determine if there was an effect of MON 863 or insecticide regime on that taxonomic group. 3. This report describes the results of a power analysis to determine the ability of the study design to detect an effect of MON 863 corn on the abundance of different groups of arthropods. A 50% difference in average taxon abundance between MON 863 and conventional corn plots was the criterion used in assessing the power. 4. A statistical power analysis of the taxonomic group comparisons made in the 2‐year field study (with independent assignment of treatments each year) showed that only about 28% (22 of 56) of the statistical comparisons made with single years of data achieved ≥80% power to detect a 50% difference in population density. When data from both years of the study were analysed jointly, this level of power was obtained for 86% (24 of 28) the comparisons made. 5. Graphical examination of the mean abundance and coefficient of variation (CV) for different taxa indicated that high abundance (> 5 trap captures per plot per sampling period) and low CV (< 100%) contributed to high statistical power (> 80%). Taxa with extremely low abundance (mean trap captures < 1 individual per plot per sampling period) generally had high CV (> 100%), and statistical comparisons for those taxa had lower power (< 80%). 6. The relevance of these findings for designing field studies on the effects of genetically modified crops on non‐target arthropods with desired levels of power is discussed.