A New Liquid Medium for Trypanosoma (Schizotrypanum) cruzi*

A new liquid medium, with fetal calf serum as the sole undefined component, was devised for the cultivation of Trypanosoma cruzi. The need for the serum is ascribed to its mitogenic proteins, which stimulate division of, and the uptake of [³H]thymidine by the parasites. In the new medium, T. cruzi has a cycle culminating in the appearance of up to 90% metacyclic forms in the stationary phase. This cycle is repeated on each serial transfer.     

An Improved Method for the Isolation of Highly Polymerized Native Deoxyribonucleic Acid from Certain Protozoa*

A relatively simple phenol extraction method, with EDTA as the nuclease inhibitor, is described for the isolation of purified, highly polymerized native DNA from Trichomonas vaginalis, Trichomonas gallinae, and Tritrichomonas foetus; it is applicable also to Tetrahymena pyriformis. RNase Tl, RNase A (Worthington's R), pronase, and α-amylase digestions constitute important steps in obtaining satisfactory yields of DNA. High degree of polymerization of the isolation product was estimated by hyperchromicity at O.D.₂₆₀ after DNase treatment and by CsCl gradient analysis. The double-stranded condition of the DNA samples was estimated by the latter method and by denaturation with NaOH, and the molecular weight by sucrose gradient analysis. Purity of the samples was determined spectrophotometrically and by chemical analyses for protein and glycogen. DNA percent recovery was estimated by the diphenylamine reaction.     

Eimeria macusaniensis n. sp. (Protozoa: Eimeriidae) of the Alpaca Lama pacos

SYNOPSIS. A new species of coccidium, Eimeria macusaniensis n. sp., is described from the alpaca Lama pacos in Macusani, Peru. The oocysts are ovoid to piriform, 81–107 by 61–80 μ (mean 93.6 by 67.4 μ) with a micropylar cap and elongate ovoid sporocysts 33–40 by 16–20 μ (mean 36.3 by 18.3 μ).     

Ants impact the energy reserves of natural enemies through the shared honeydew exploitation

1. Ants, as well as many species of parasitoids and predators, rely on sugar‐rich foods such as honeydew to fulfill their energetic needs. Thus, ants and natural enemies may interact through the shared honeydew exploitation. 2. Ant‐exclusion experiments were performed in a citrus orchard to test the hypothesis that ants may impact the energy reserves of predators and parasitoids through the competition for honeydew. Through the use of high‐performance liquid chromatography (HPLC) the level of ant activity with the energy reserves and feeding history of individual specimens collected in the field during representative days of spring, summer, and autumn were related. 3. Out of 145 Aphytis chrysomphali Mercet parasitoids captured in the field, 65% were classified as sugar‐fed and 24.7% as honeydew‐fed. In summer, when ant activity peaked, there was a significant negative correlation between the level of ant activity and the total sugar content and honeydew feeding incidence by A. chrysomphali. Out of 47 individuals of the predator Chrysoperla carnea sensu lato (Stephens), captured in the field, 55.3% were classified as sugar‐fed. We found a significant negative effect of the level of ant activity on the sugar‐feeding incidence by C. carnea in spring. 4. The present study provides evidence that ants can interfere with the energy reserves of natural enemies. This interaction may be widespread in various ecosystems with important consequences for the arthropod community composition and with practical implications for biological control given that absence of sugar feeding is detrimental for the fitness of many species of predators and parasitoids.     

Observations on Bacterial Feeding by the Rumen Ciliate Isotricha prostoma

SYNOPSIS. Starvation of Isotricha prostoma for 72–96 hours decreased the cellular amylopectin granules and facilitated the microscopic search for bacterial feeding. I. prostoma selected and ingested only certain rods from among many types of rumen bacteria. In order to isolate the bacteria important as a food source for Isotricha , the starved protozoa were allowed to feed on mixed rumen bacteria, washed, and the crushed protozoan contents quickly cultured for bacteria. Several strains of bacteria were isolated in pure culture. Three of the rod strains isolated were rapidly ingested by I. prostoma when fed to the ciliate. In a monobacterial culture I. prostoma divided once before succumbing.     

Tracking the origin of an invasive species: Drosophila subobscura in Argentina

Biological invasions are excellent opportunities to study the evolutionary forces leading to the adaptation of a species to a new habitat. Knowledge of the introduction history of colonizing species helps tracking colonizing routes and assists in defining management strategies for invasive species. The Palearctic species Drosophila subobscura is a good model organism for tracking colonizations since it was detected in Chile and western North America three decades ago and later on in the Atlantic coast of Argentina. To unravel the origin of the Argentinean colonizers two populations have been analysed with several genetic markers. Chromosomal arrangements and microsatellite alleles found in Argentina are almost similar to those observed in Chile and USA. The lethal allelism test demonstrates that the lethal gene associated with the O₅ inversions in Argentina is identical to that found in Chile and USA, strongly supporting the hypothesis that all the American colonizing populations originated from the same colonization event. A secondary bottleneck is detected in the Argentinean populations and the genetic markers suggest that these populations originated from the invasion of 80–150 founding individuals from Chile.     

INFLUENCE OF EDUCATION/PROFESSION OF MEXICAN CONSUMERS ON ACCEPTANCE AND PURCHASE INTENT OF CORN TORTILLA

Influence of education/profession of Mexican consumers on acceptance and purchase intent of corn tortillas was evaluated. Two groups of 150 Mexican consumers each (faculty/graduate students [A] versus field laborers [B]) rated sensory acceptability of corn tortillas. Acceptance and purchase intent were rated using a binomial scale. Group B had higher expectations towards corn tortillas as indicated by lower acceptability ratings. Both groups used rollability, resistance-to-tearing, and chewiness to differentiate tortilla samples, but group B paid more attention to these attributes as indicated by higher canonical correlation values. Acceptance was influenced by overall liking for both groups; chewiness and taste were also significant for group B. Purchase intent was influenced by overall liking and taste for both groups, but color for group A, and appearance and chewiness for group B were also critical. This study demonstrated that education/profession of Mexican consumers affected their acceptance and purchase intent of corn tortillas.

PRACTICAL APPLICATIONS

This study revealed that education/profession of Mexican consumers affected acceptance and purchase intent of corn tortillas. Two groups of consumers with different levels of education had different expectation toward tortillas when making purchase decision. Understanding how each consumer segment differently perceives about the tortilla product will give marketers and manufacturers a better direction for developing tortilla products with expected sensory qualities.     

Aboveground plant biomass,carbon, and nitrogen dynamics before and after burning in a seminatural grassland of Miscanthus sinensis in Kumamoto,Japan

Although fire has been used for several thousand years to maintain Miscanthus sinensis grasslands in Japan, there is little information about the nutrient dynamics in these ecosystems immediately after burning. We investigated the loss of aboveground biomass; carbon (C) and nitrogen (N) dynamics; surface soil C change before and after burning; and carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) fluxes 2 h after burning in a M. sinensis grassland in Kumamoto, Japan. We calculated average C and N accumulation rates within the soil profile over the past 7300 years, which were 58.0 kg C ha^?1 yr^?1 and 2.60 kg N ha^?1 yr^?1, respectively. After burning, 98% of aboveground biomass and litter were consumed. Carbon remaining on the field, however, was 102 kg C ha^?1. We found at least 43% of C was possibly lost due to decomposition. However, remaining C, which contained ash and charcoal, appeared to contribute to C accumulation in soil. There was no difference in the amount of 0–5 cm surface soil C before and after burning. The amount of remaining litter on the soil surface indicated burning appeared not to have caused a reduction in soil C nor did it negatively impact the sub‐surface vegetative crown of M. sinensis. Also, nearly 50 kg N ha^?1 of total aboveground biomass and litter N was lost due to burning. Compared with before the burning event, postburning CO₂ and CH₄ fluxes from soil appeared not to be directly affected by burning. However, it appears the short time span of measurements of N₂O flux after burning sufficiently characterized the pattern of increasing N₂O fluxes immediately after burning. These findings indicate burning did not cause significant reductions in soil C nor did it result in elevated CO₂ and CH₄ emissions from the soil relative to before the burning event.