Chromosome numbers and meiotic analysis in the pre-breeding of <Emphasis Type="BoldItalic">Brachiaria decumbens</Emphasis> (Poaceae)

A total of 44 accessions of Brachiaria decumbens were analysed for chromosome count and meiotic behaviour in order to identify potential progenitors for crosses. Among them, 15 accessions presented 2n = 18; 27 accessions, 2n = 36; and 2 accessions, 2n = 45 chromosomes. Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness and abnormal cytokinesis were observed in low frequency. All abnormalities can compromise pollen viability by generating unbalanced gametes. Based on the chromosome number and meiotic stability, the present study indicates the apomictic tetraploid accessions that can act as male genitor to produce interspecific hybrids with B. ruziziensis or intraspecific hybrids with recently artificially tetraploidized accessions.     

PROBLEMS WITH SAMPLING DESERT TORTOISES: A SIMULATION ANALYSIS BASED ON FIELD DATA

Abstract: The desert tortoise (Gopherus agassizii) was listed as a U.S. threatened species in 1990 based largely on population declines inferred from mark-recapture surveys of 2.59-km² (1-mi²) plots. Since then, several census methods have been proposed and tested, but all methods still pose logistical or statistical difficulties. We conducted computer simulations using actual tortoise location data from 2 1-mi² plot surveys in southern California, USA, to identify strengths and weaknesses of current sampling strategies. We considered tortoise population estimates based on these plots as “truth” and then tested various sampling methods based on sampling smaller plots or transect lines passing through the mile squares. Data were analyzed using Schnabel's mark-recapture estimate and program CAPTURE. Experimental subsampling with replacement of the 1-mi² data using 1-km² and 0.25-km² plot boundaries produced data sets of smaller plot sizes, which we compared to estimates from the 1-mi² plots. We also tested distance sampling by saturating a 1-mi² site with computer simulated transect lines, once again evaluating bias in density estimates. Subsampling estimates from 1-km² plots did not differ significantly from the estimates derived at 1-mi². The 0.25-km² subsamples significantly overestimated population sizes, chiefly because too few recaptures were made. Distance sampling simulations were biased 80% of the time and had high coefficient of variation to density ratios. Furthermore, a prospective power analysis suggested limited ability to detect population declines as high as 50%. We concluded that poor performance and bias of both sampling procedures was driven by insufficient sample size, suggesting that all efforts must be directed to increasing numbers found in order to produce reliable results. Our results suggest that present methods may not be capable of accurately estimating desert tortoise populations.     

EFFECT OF AN OXYGEN-REDUCING MEMBRANE FRACTION ON HELICOBACTER PYLORI

The emerging gastric pathogen Helicobacter pylori is an oxygen-sensitive fastidious microaerophile. Culturability of this organism is rapidly lost in oxygen levels present in the atmosphere due to its morphological transformation into a viable but not culturable state. The effect of the Oxyrase^TM system of oxygen-reducing membrane fragments on H. pylori was evaluated at levels ranging from 0.1 to 0.6 Units/mL in Brucella broth supplemented with 5% horse serum. Duplicate sets of Oxyrase^TM dilutions inoculated with H. pylori were incubated at 35C aerobically and microaerobically. At these Oxyrase^TM levels, a logarithmic loss of H. pylori viability was evident in the aerobic cultures. The inoculum remained recoverable for 24 h in the presence of Oxyrase^TM, whereas recovery of inoculum in untreated broth was greatly reduced after 8 h of aerobic incubation, and the organism was unrecoverable after 24 h. Oxyrase^TM-containing broth cultures of H. pylori incubated microaerobically showed a similar drop in viable counts for the first 48 h of incubation; however, at the lower levels of Oxyrase^TM, some cells survived, and resumed logarithmic growth at 96 h. To explore the effects of short term aerobic incubation in the presence of 0, 0.005, 0.05, and 0.5 Units Oxyrase^TM, cultures were examined microscopically after 4, 8, and 24 h. In the Oxyrase^TM-containing broths, <90% of the cells exhibited rod shape morphology after 8 h, whereas in the untreated broth, most cells appeared coccoid. After 24 h, all cells exhibited coccoid morphology.     

Purification and Characterization of Clathrin-Coated Vesicles from Chlamydomonas

Clathrin-coated vesicles, identified by negative staining with uranyl acetate, were purified from Chlamydomonas rein-hardtii. Isolated coated vesicles had diameters ranging from 70 to 140 nm (mean diameter±SD of 95±17 nm, n=300). These vesicles were markedly heterogeneous in both density and surface charge, as indicated by equilibrium density sedimentation and elution from anion-exchange columns. Highly-purified coated-vesicle fractions contained 2 major polypeptides, identified as the clathrin heavy chain (185 kDa) and the clathrin light chain (40 kDa). Chlamydomonas clathrin heavy chain cross-reacts weakly with an antibody against bovine brain clathrin heavy chain. Coat stability in several buffers was compared to that of bovine brain coated vesicles. Stability was similar, except for a greater stability of Chlamydomonas coated vesicles in 0.5 M Tris at pH 7.0.     

Women's Preponderance in Possession Cults: The Calcium-Deficiency Hypothesis Extended

The preponderance of women in spirit possession cults is linked with the likelihood of deficiencies in thiamine, tryptophan-niacin, calcium, and vitamin D in women in Old World traditional societies in which poverty and/or sumptuary rules restrict women's nutrient intakes more than those of men. The higher nutrient needs of pregnant and lactating women may exacerbate the inadequacy of their diets. It is postulated that involuntary symptoms of deficiencies affecting the central nervous system and muscles have been recognized in these societies as manifestations of spirit possession and institutionalized as a means of reducing victims' anxieties and restoring their ability to function normally     

Importance of colour in the reaction of passerine predators to aposematic prey: experiments with mutants of Pyrrhocoris apterus (Heteroptera)

Persistent questions concerning the warning coloration of unpalatable insects address whether the bright aposematic colour itself or its combination with a species-specific dark pattern is the key factor in their protection against insectivorous birds, and how chromatic polymorphism originates and is maintained in aposematics. In the present study, these questions were tested experimentally, using the birds Parus major , Parus caeruleus , Erithacus rubecula , and Sylvia atricapilla as predators, and chromatically polymorphic firebug Pyrrhocoris apterus : red wild form, white, yellow, and orange mutants (all four of them with the same black melanin pattern, the mutants differing in colour of pteridine pigments only) and the nonaposematic brown-painted wild form as prey. The results show that a specific colour is essential for the birds to recognize the specific aposematic prey; the melanin pattern is not sufficient. White mutants were no better protected than nonaposematic firebugs; red wild-type and orange mutants were equally well protected against all bird species; and the reaction of birds to yellow mutants was species-specific. An evolutionary scenario of 'recurrent recessive mutations' is formulated to explain the origin of colour polymorphism in some aposematics.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 143–153.     

The first parasitic Trichoptera

Abstract.

• 1 A parasitoid habit is confirmed in larvae of an Australian micro-caddisfly, Orthotrichia muscari Wells, being the first known incidence of this habit in the order Trichoptera.
• 2 Larvae of O.muscari are non-specific parasites of pupae of other caddisfly species.
• 3 O.muscari is in an Australian/New Guinean/SE Asian species group in Orthotrichia, all members of which probably share the habit. Their larvae and pupae have atypical features that are interpreted as adaptations to their uncharacteristic niche.