Isolation of ergosterol peroxide and its reversion to ergosterol in the pathogenic fungus Sporothrix schenckii

Ergosterol peroxide, a presumed product of the H2O2-dependent enzymatic oxidation of ergosterol, has been isolated from yeast from yeast forms of the pathogenic fungus Sporothrix schenckii. The substance, which may have a role in fungal virulence, has been characterized mainly using spectroscopic methods (1H and 13C nuclear magnetic resonance and high resolution mass spectra). The purified compound showed a molecular formula of C28H44O3, displaying characteristic features of epidioxy sterols and was reverted to ergosterol when submitted to S. schenckii enzymatic extract.

Honey Ants (Genus Myrmecocystus) Macroecology: Effect of Spatial Patterns on the Relationship between Worker Body Size and Geographic Range Size

Macroecology evaluates the partitioning of physical space and resources among organisms through correlation among ecological variables, such as geographical range size and shape, body size, and population density, measured at large geographical and taxonomic scales. In this article, we analyzed the spatial patterns in worker body size and geographic range size for the 27 described species of honey ants, genus Myrmecocystus Wesmael, in the United States and Mexico, and especially the relationship between these 2 variables after statistically removing their spatial patterns. The 2 variables are correlated, but also displayed significant spatial patterns, as detected by trend surface and spatial autocorrelation analyses. After removing these spatial effects, worker body size and geographic range size were still positively correlated. The relationship, therefore, is not a consequence of spatial effects and it does follow Brown's model, which predicts that the geographic range size will have a positive slope on body size. In this model, the lower population densities caused by foraging activities and local territorial competition are associated with a large geographic range, avoiding stochastic extinction. Although this constraint in local population density does not necessarily hold for small organisms such as insects that could achieve high densities even in very small areas and patchy habitats, it may hold for social insects, especially ants, because of the local competition among colonies.

Attack on Chestnut-bellied Euphonia nestlings by army ants

I report some observations of a Chestnut-bellied Euphonia (Euphonia pectoralis) nest in a lowland Atlantic Forest of southeastern Brazil during the early nestling period. During 7.5 hours of observations, the nest was attended 46.3% of the time, 45.6% by the female and 0.7% by the male. Unattended periods lasted 16-38 min. Parents visited the nest most of the time together at 36-59 min intervals. There were 1.06 feeding visits per nestling per hour. The two nestlings in the nest ended up preyed upon by army ants (Labidus praedator, Ecitoninae). The low height of the nest (0.8 m) may have facilitated its detection by the ants.

A kinetic model of phosphorus metabolism in growing goats

The effect of increasing phosphorus (P) intake on P utilization was investigated in balance experiments using 12 Saanen goats, 4 to 5 mo of age and weighing 20 to 30 kg. The goats were given similar diets with various concentrations of P, and 32P was injected to trace the movement of P in the body. A P metabolism model with four pools was developed to compute P exchanges in the system. The results showed that P absorption, bone resorption, and excretion of urinary P and endogenous and fecal P all play a part in the homeostatic control of P. Endogenous fecal output was positively correlated to P intake (P < .01). Bone resorption of P was not influenced by intake of P, and P recycling from tissues to the blood pool was lesser for low P intake. Endogenous P loss occurred even in animals fed an inadequate P diet, resulting in a negative P balance. The extrapolated minimum endogenous loss in feces was .067 g of P/d. The minimum P intake for maintenance in Saanen goats was calculated to be .61 g of P/ d or .055 g of P/(kg.75·d) at 25 kg BW. Model outputs indicate greater P flow from the blood pool to the gut and vice versa as P intake increased. Intake of P did not significantly affect P flow from bone and soft tissue to blood. The kinetic model and regressions could be used to estimate P requirement and the fate of P in goats and could also be extrapolated to both sheep and cattle.

Growth of Dendrobium nobile Lindl. as related with nutrient concentration in the growing media

Dendrobium nobile orchids were grown for three years in different substrates (tree fern fiber, blocks of pressed coconut bark, bark of Eucalyptus grandis, mixtures with coconut bark blocks and eucalyptus bark and mixtures with the latter materials and charcoal. Plant growth increased with higher concentrations of S (up to 1.6 g/kg), Cu (up to 46 mg/kg) and Zn (up to 147 mg/kg), and decreased with higher concentrations of Ca (up to 13.2 g/kg), Mg (up to 6.6 g/kg) and B (up to 19 mg/kg). High Mo (up to 5.3 mg/kg) caused a more intense loss of leaves after planting. Relations between nutrient concentrations also affected plant growth. With exception of eucalyptus bark, all growing media under study were suitable for plant growth.

Effects of cervical headgear and edgewise appliances on growing patients

Maxillary basal bone, dentoalveolar, and dental changes in Class II Division 1 patients treated to normal occlusion by using cervical headgear and edgewise appliances were retrospectively evaluated. A sample of 45 treated patients was compared with a group of 30 untreated patients. Subjects were drawn from the Department of Orthodontics, Araraquara School of Dentistry, Brazil, and ranged in age from 7.5 to 13.5 years. The groups were matched based on age, gender, and malocclusion. Roughly 87% of the treated group had a mesocephalic or brachicephalic pattern, and 13% had a dolicocephalic pattern. Cervical headgear was used until a Class I dental relationship was achieved. Our results demonstrated that the malocclusions were probably corrected by maintaining the maxillary first molars in position during maxillary growth. Maxillary basal bone changes (excluding dentoalveolar changes) did not differ significantly between the treated and the untreated groups. Molar extrusion after the use of cervical headgear was not supported by our data, and this must be considered in the treatment plan of patients who present similar facial types. (Am J Orthod Dentofacial Orthop 2001;119:531-9).

Susceptibility of the cattle tick Boophilus microplus (Acari: Ixodidae) to isolates of the fungus Beauveria bassiana

The susceptibility of the tick Boophilus microplus to Beauveria bassiana was evaluated by inoculating eggs, larvae and engorged females of the tick with five fungal isolates at concentrations of 106, 107 and 108 conidia/ml. Tick eggs (0.25 g) were immersed in 1 ml of a suspension of the different conidial concentrations for 1 min. Similar exposure was performed by immersion of 2000 larvae and homogeneous groups of nine engorged females in 2 and 20 ml of conidial suspension, respectively. Treated eggs, larvae and adults were placed in an incubator at 27 ± 1 °C and relative humidity above 80% for evaluation of the fungal action. All fungal isolates applied at all conidial concentrations reduced the hatching rate of larvae from treated eggs by 1.36-65.58% and increased the mortality rate of inoculated larvae by 0.8-70.49%. In the bioassay with engorged females, oviposition period was reduced by 9.69-47.80%, egg mass weight by 4.71-53.87%, estimated reproduction by 8.3-60.62%, egg production index by 5.03-54.20%, percent larval hatching by 0.27-13.96%, and the mortality rate of treated females was increased by 96.60-100%. The reduction of the estimated reproduction obtained for the treated groups ranged from 8.37 to 64.52%. The sporulation of the pathogen on dead females ranged from 3.70 to 88.88% depending on the isolate and concentration used. Isolates AM 09, CB 7 and JAB 07 were the most effective and effectiveness increased with increasing concentrations of conidia in the suspensions.

Size and lipid content of nonmyrmecochorous diaspores: Effects on the interaction with litter-foraging ants in the Atlantic rain forest of Brazil

Ants are often attracted to diaspores not adapted for dispersal by ants. These diaspores may occasionally benefit from this interaction. We selected six nonmyrmecochorous plant species (Virola oleifera, Eugenia stictosepala, Cabralea canjerana, Citharexylum myrianthum, Alchornea glandulosa and Hyeronima alchorneoides) whose diaspores differ in size and lipid content, and investigated how these features affect the outcome of ant-diaspore interactions on the floor of a lowland Atlantic forest of Southeast Brazil. A total of 23 ant species were seen interacting with diaspores on the forest floor. Ants were generally rapid at discovering and cleaning the diaspore pulp or aril. Recruitment rate and ant attendance were higher for lipid-rich diaspores than for lipid-poor ones. Removal rate and displacement distance were higher for small diaspores. The large ponerine ant Pachycondyla striata, one of the most frequent attendants to lipid-rich arillate diaspores, transported the latter into their nests and discarded clean intact seeds on refuse piles outside the nest. Germination tests with cleaned and uncleaned diaspores revealed that the removal of pulp or aril may increase germination success in Virola oleifera, Cabralea canjerana, Citharexylum myrianthum and Alchornea glandulosa. Gas chromatography analyses revealed a close similarity in the fatty acid composition of the arils of the lipid-rich diaspores and the elaiosome of a typical myrmecochorous seed (Ricinus communis), corroborating the suggestion that some arils and elaiosomes are chemically similar. Although ant-derived benefits to diaspores - secondary dispersal and/or increased germination - varied among the six plant species studied, the results enhanced the role of ant-diaspore interactions in the post-dispersal fates of nonmyrmecochorous seeds in tropical forests. The size and the lipid-content of the diaspores were shown to be major determinants of the outcome of such interactions.

Histological, histochemical and morphometric study of female corpora allata of Pachycondyla striata ants (Hymenoptera: Ponerinae)

In this study we utilized both histological/histochemical tests and morphometric/statistical tests to observe developmental differences in the corpora allata in Pachycondyla striata workers and queens ants. The general structure of corpora allata was similar between workers and queens. The differences found among the volumes was not statistically significant when the probability value was set at 5%. Although the queen corpora allata volume has been observed smaller than those of the worker and the right gland volume has been smaller than those of the left one. Differences also were observed histologically, the worker corpora allata cells showed homogeneous cytoplasm and sparse nuclear chromatin in well defined nuclei. It was the reverse in the queens, in which the corpora allata cells showed some secretory cytoplasmic vesicles and nuclei with a different morphology, i. e., from extremely large with sparse chromatin to small with condensed chromatin. Employing histochemical tests verified that the corpora allata in both castes contained large amounts of RNA and protein in the cytoplasm of their cells and an absence of polysaccharides. Differences in the lipid amounts in worker's glands were found, whereas, in the queens' corpora allata lipids always occur.

Purification and characterization of two β-glucosidases from the thermophilic fungus Thermoascus aurantiacus

β-Glucosidase from the fungus Thermoascus aurantiacus grown on semi-solid fermentation medium (using ground corncob as substrate) was partially purified in 5 steps-ultrafiltration, ethanol precipitation, gel filtration and 2 anion exchange chromatography runs, and characterized. After the first anion exchange chromatography, β-glucosidase activity was eluted in 3 peaks (Gl-1, Gl-2, Gl-3). Only the Gl-2 and Gl-3 fractions were adsorbed on the gel matrix. Gl-2 and Gl-3 exhibited optimum pH at 4.5 and 4.0, respectively. The temperature optimum of both glucosidases was at 75-80°C. The pH stability of Gl-2 (4.0-9.0) was higher than Gl-3 (5.5-8.5); both enzyme activities showed similar patterns of thermostability. Under conditions of denaturing gel chromatography the molar mass of Gl-2 and Gl-3 was 175 and 157 kDa, respectively. Using 4-nitrophenyl β-D-glucopyranoside as substrate, Km values of 1.17 ± 0.35 and 1.38 ± 0.86 mmol/L were determined for Gl-2 and Gl-3, respectively. Both enzymes were inhibited by Ag+ and stimulated by Ca2+.

Post-selection and return of foraged material by Acromyrmex subterraneus brunneus (Hymenoptera: Formicidae)

Two colonies of Acromyrmex subterraneus brunneus Forel (Hymenoptera: Formicidae) were studied regarding their behavior during cultivation of the fungus garden to determine a) the existence of post-selection of foraged material by the workers, and b) if present, the mechanism of this discrimination and how this material is returned. Many studies on plant processing by leaf-cutting ants have been carried out, but none of them has investigated the decision-making process of workers in the case of erroneous food selection. For this purpose, material with different degrees of moisture and hardness (floral sponge, polystyrene, plastic and clay) were individually offered to the colonies and the tasks performed by the different size categories were carefully recorded. Three tasks, i.e., foraging, cultivation of the fungus garden and return of the foraged material, were studied and subdivided into 14 subtasks. Analysis of all inert materials as a whole showed the presence of post-selection of foraged material through the return of material inadequate for the workers and the fungus. Discrimination of the inert material was observed at the time of shredding, probably based on parameters such as physical resistance to cutting and moisture content. A. s. brunneus workers showed flexibility in their activities during substrate processing. The observed post-selection of foraged material provides strong evidence for the cognitive abilities of worker ants and of the colony as a whole. Polymorphism and a complex society represent vital characteristics for the ecological success of this species.

The effect of trail length on task partitioning in three Acromyrmex species (Hymenoptera: Formicidae)

By comparing the behavior of three Acromyrmex (Hymenoptera, Formicidae) species during foraging on artificial trails of different lengths, we observed the occurrence of task partitioning and its relation to the food distance from the nest. Task partitioning was verified by leaf cache formation along the trail and leaf direct transferring among workers. There was significant difference between the number of leaf fragments carried directly to the fungus chamber and those transferred direct or indirectly, via cache, depending upon the trail length. Task partitioning could be a strategy used by leaf-cutting ants that allows the workers to use food sources far from their nests.

Reciprocal interference between ants and stingless bees attending the honeydew-producing homopteran Aetalion reticulatum (Homoptera: Aetalionidae)

We evaluated the reciprocal effects between foragers of the ants Camponotus crassus and of the stingless bees Trigona hyalinata on aggregations of the honeydew-producing treehopper Aetalion reticulatum. The interactions were observed in Bauhinia variegata (Caesalpiniaceae) and Mangifera indica (Anacardiaceae) trees. We recorded the presence/absence of each attendant species in homopteran aggregations to test if the observed co-occurrence is lower than that expected by chance. An exclusion experiment was performed in which each attendant species was excluded from aggregations in order to test if an attendant species is more likely to occupy aggregations where the other attendant is not present. We also recorded the number of individuals of each attendant species in homopteran aggregations to search for any correlation between homopteran and attendant abundances. Additionally, we performed experiments using termites (Termitidae, Isoptera) as models to verify if the attendant species have the potential to defend A. reticulatum against natural enemies. The co-occurrence of attendant species was lower than that expected by chance. Homopteran aggregations without stingless bees were more visited by ants than those in which T. hyalinata was present, and vice-versa. The abundance of stingless bees was proportional to homopteran abundance, while ants abundance was not correlated to homopteran abundance. Both attendant species attacked the natural enemies models when we glued the termites ca. 1 cm away from homopteran aggregations, but only ants removed termites glued 5-7 cm away from aggregations. We suggest that the effects of non-formicid attendants should be included as another factor influencing the costs and benefits of ant-homopteran interactions, since honeydew availability for ants also depends on the presence and behavior of interspecific attendants.

Cultivation systems and planting seasons effects on the vegetative growing of net melon cultivars

Growth effects of cultivation on soil, sand and commercial substrate, on summer and winter time, of 'Bonus #2', 'Don Carlo's and 'Hy Mark' were assessed. The experiments were conducted in a greenhouse of FCAV-UNESP, in Jaboticabal- SP, Brazil, 21° 15' 22 S, 48° 18'58 W, and an altitude of 595 m, comprising the period from November '99 to April 2000 (Summer), and from July to November 2000 (Winter). On soil cultivation, chemical nutrients were used, and the plants received drip irrigation. On sand, fertigation with recirculation of the nutrient solution were used, and slabs and fertigation with non circulating nutrient solution was used with commercial substrate. 'Bonus #2', grown on sand and in the summer season had improved plant height, internodes length, stem diameter, leaf area and dry matter of shoots and roots. 'Hy Mark', when cultivated on commercial substrate had lower growth. During winter season, the growth was slower.