Key attributes to the disturbance response of montane cloud forest trees: shade tolerance,dispersal mode and the capacity to form a seed bank

? Context

Understanding the biological mechanisms related to plant response to disturbance is essential for predicting the changes in the structure of plant communities resulting from disturbance.

? Aims

The aims of this study are to identify the regeneration traits linked to the response to disturbance of tree species of a montane cloud forest in order to define regeneration types and to explore whether disturbance intensity acts to select specific regeneration types that can colonize disturbed plots.

? Methods

A theoretical model was developed and evaluated using structural equation modeling to link two latent variables: regeneration type and vulnerability to disturbance. We studied two plots that were subjected to different intensities of disturbance and one plot of mature forest.

? Results

Shade tolerance, dispersal mode, and the capacity to form a seed bank were the traits that determine regeneration type. There was a trend for re-sprouting capacity to be associated with the regeneration types dominant in disturbed plots. Regeneration types were differentially distributed among the sites.

? Conclusion

There was evidence that disturbance intensity has a filtering effect on the colonization of disturbed plots. Species vulnerability to disturbance depends on specific combinations of regeneration traits. Structural equation modeling is useful for exploring plant response to disturbance using key parameters linked to plant persistence.     

Risk factors and spatial distribution of urban rat infestations

Urban rat infestations have multifactorial causes and may result in severe public health and environmental problems, as well as heavy economic losses. The identification of putative environmental determinants of urban rat infestations and the mapping of areas prone to experiencing such infestations (hot spots) are crucial for effectively addressing intervention efforts. We investigated the associations between a selection of environmental factors and the occurrence of rat infestations in the city of Madrid, Spain. This was done by modelling 10,956 citizen-reported rat sightings from 2002 to 2008 using generalized additive models, both at municipality (Madrid) and district (Latina) levels. Increased age and density of housing, and decreased distance to vegetated areas, markets and cat feeding stations were factors associated with an increased risk of rat infestations. Risk maps for rat infestations were also developed and recurrent hot spots of rat activity were identified. Although a better fit to the data was obtained in the model for the smaller scale and possibly more environmentally homogenous study area of Latina, modelling the spatial distribution of rat sightings was useful for identifying factors associated with an increased risk of urban rat infestations, as well as for identifying hot spots of rat activity, providing local authorities with a practical tool for effectively targeting intervention efforts to high-risk situations based on the local environmental contexts.     

Performance of Nellore heifers, forage mass, and structural and nutritional characteristics of Brachiaria brizantha grass in integrated production systems

Our objective was to evaluate production, nutritive value and carrying capacity of piatã grass (Brachiaria brizantha cv. BRS Piatã), and performance of Nellore heifers in agrosilvopastoral systems (ASPS) with three eucalyptus (Eucalyptus urograndis) tree densities, during winter, spring, summer, and fall. Three integrated systems were evaluated: ASPS-1 (357 trees ha^?1), ASPS-2 (227 trees ha^?1), and CON (5 trees ha^?1). In each system, two sward heights were evaluated: short and tall. A total of 80 11-month-old Nellore heifers were randomly allocated in a randomized split-plot block, 3?×?2 factorial. Greater dry matter availability was observed on CON pastures during the fall season. Greater percentage of leaf lamina was detected on ASPS-1 with short sward height and greater during summer, compared with other seasons. A greater forage production was observed between tree rows and for tall sward height. Spring was the season with less forage nutritive value. Average daily gain was greater during summer and fall. Gain per hectare and stocking rate were greater on CON system and on ASPS-2. Pastures with short sward height had greater gain per hectare and stocking rate. Agrosilvopastoral systems with intermediate tree density seem to be a good choice for producers willing to diversify their revenue sources without decreasing animal production.     

Predatory capability of the nematophagous fungus Arthrobotrys robusta preserved in silica gel on infecting larvae of Haemonchus contortus

Biological control of gastrointestinal nematodiasis in ruminants is an alternative to reduce the number of infective larvae. The fungal isolates predatory activity preservation is a basic requirement for the success of this control type. The aim of this work is to evaluate the predatory capacity of the fungus Arthrobotrys robusta (isolate I-31), preserved on silica gel on infective larvae of Haemonchus contortus under laboratory conditions on 2 % water agar (2 % WA). In this essay, A. robusta storage on silica gel showed successful predatory activity on H. contortus L₃ larvae (p?<?0.01) compared to the control group. Nematophagous fungi were not observed in the control group during the experiment. There was a significant reduction (p?<?0.01) of 73.84 % in the means of H. contortus (L₃) recovered from treatment with isolate I-31 compared to the control without fungi. Results indicate that A. robusta (I-31) could survive stored on silica gel for at least 7 years and keep its predatory activity on H. contortus (L₃).     

Neospora caninum DNA detection by TaqMan real-time PCR assay in experimentally infected pregnant heifers

Neosporosis has been considered the main cause of abortion between the first and the second trimester of pregnancy in cattle. Therefore, the objective of this study was to identify the presence of Neospora caninum DNA obtained from experimental models based on the evaluation of different areas of the fetal nervous system and organs from heifers previously inoculated with NC-1 after or before insemination. This study was performed with Hereford × Nelore (n = 29) heifers and all animals were considered free of diseases at the beginning of the experiment. All animals were bred by fixed-time artificial insemination (TAI) and allocated as follows: (a) seronegative heifers subjected to TAI (TAI, n = 9), (b) heifers infected with N. caninun 60 days prior to TAI (NC-1 + TAI, n = 9), and (c) heifers submitted to TAI and infected with N. caninum 60 days later (TAI + NC-1, n = 11). The pregnancy was confirmed by transrectal ultrasonography 35 days after TAI and evaluated every 30 days until the end of gestation. Fetuses were collected surgically at 170 days of gestation, and immediately necropsied to remove tissues aseptically. Samples of the central nervous system (CNS), heart, kidney, lung, liver, skeletal muscle and caruncle were collected for DNA extraction. Days of gestation at abortion and interval from abortion to first insemination were examined by Student's t-test. At 35 days of gestation the pregnancy rates in the group NC-1 + TAI (4/9, 44.4%) was lower than in the control group (8/9, 88.8%, P < 0.05). At 60 days, the pregnancy rates in the NC-1 + TAI group (0/4, 0%) was lower compared to TAI + NC-1 (5/7, 71.4%) and control (6/8, 75.0%) groups (P < 0.05). Animals from the group NC-1 + TAI were re-inseminated 60 days after the first TAI. After pregnancy losses throughout the study, 5 animals (TAI), 3 animals (NC-1 + TAI) and 5 animals (TAI + NC-1) maintained pregnancy until 170 days of gestation. TaqMan RT-PCR demonstrated the presence of N. caninum DNA in the medulla and right posterior cortex in 3 out of 5 fetuses from the TAI + NC-1 group. We concluded that heifers infected after TAI had a higher incidence of the parasite at the fetus CNS. Identification of N. caninum by TaqMan RT-PCR would assist in the investigation of infection and in the evaluation of vaccines or therapeutic drugs to control neosporosis in cattle.     

Experimental infection of house sparrows (Passer domesticus) with West Nile virus isolates of Euro-Mediterranean and North American origins

West Nile virus (WNV) is a zoonotic arboviral pathogen transmitted by mosquitoes in a cycle involving wild birds as reservoir hosts. The virus has recently emerged in North America and re-emerged in Europe. North American WNV outbreaks are often accompanied by high mortality in wild birds, a feature that is uncommon in Europe. The reason for this difference is unknown, but the intrinsic virulence of the viruses circulating in each continent and/or the susceptibility to the disease of Palearctic as opposed to Nearctic wild bird species could play a role. To assess this question, experimental inoculations with four lineage 1 WNV strains, three from southern Europe (Italy/2008, Italy/2009 and Spain/2007) and one from North America (NY99) were performed on house sparrows (Passer domesticus), a wild passerine common in both continents. Non-significant differences which ranged from 0% to 25% were observed in mortality for the different WNV strains. Viremias lasted from 1 to 5–6 days post-inoculation (dpi) in all cases; individuals inoculated with NY99 had significantly higher titres than those inoculated with any of the Euro-Mediterranean strains. Remarkably, host competence was found to be higher for NY99 than for the other strains. Consequently, albeit being pathogenic for house sparrows, some Euro-Mediterranean strains had reduced capacity for replication in -and transmission from- this host, as compared to the NY99 strain. If applicable also to other wild bird host species, this relatively reduced transmission capacity of the Euro-Mediterranean strains could explain the lower incidence of this disease in wild birds in the Euro-Mediterranean area.     

Treatment with eCG Decreases the Vascular Density and Increases the Glandular Density of the Bovine Uterus

The uterus plays an essential role in mammalian reproduction and is a target of several hormonal protocols used to improve fertility in cattle. Many studies highlighted the importance of eCG treatment following fixed‐time artificial insemination in improving follicular growth, ovulation and pregnancy rates in cattle. Moreover, eCG has been implicated in angiogenesis, leading to important changes in uterine blood flow and vascularisation. However, there is still a lack of information regarding the specific alterations induced by eCG upon glandular and vascular characteristics of bovine uterus. To investigate the influence of eCG on: uterine thickness and area; uterine artery diameter and area; uterine vascular and gland density; and the expression of the VEGFA‐system, the uteri of crossbred beef cows were collected. All cows were submitted to follicular wave emergence synchronization. On day four of protocol, cows submitted to superovulation (n = 6) received 2000 IU eCG, on day eight, after expected follicular deviation, cows submitted to stimulatory treatment (n = 5) received 400 IU eCG. Control cows (n = 5) did not receive eCG. On day five po cows were subjected to ultrassonographic evaluation and slaughtered for uterine tissue sampling on day six po. Uterine vessels and glands were quantified by the counting point stereological method. The VEGFA‐system was localized in different cellular types, showing no qualitative or quantitative differences in the site of expression or the intensity of the positive signal among the groups. Vascular density was decreased in the endometrium of stimulated and myometrium of superovulated cows compared with the control ones, which showed higher vascular density in the myometrium and endometrium of the ipsilateral uterine horn. The uterine gland density was higher in superovulated compared with stimulated and control cows. Thus, we can infer that stimulatory or superovulatory treatments with eCG influence the vascular density in the endometrium and myometrium in cattle.     

Follicle Deviation in Ovulatory Follicular Waves with One or Two Dominant Follicles in Mares

The follicle and hormone aspects of diameter deviation and development of one dominant (≥28 mm) follicle (1DF) vs two dominant follicles (2DF) were studied in 32 ovulatory follicular waves in mares. Follicles were ranked each day as F1 (largest) to F3. The beginning of deviation was designated day 0 and preceded the first increase in the differences in diameter between F1 and F2 in the 1DF group and between a combination of F1 and F2 vs F3 in the 2DF group. One dominant follicle and 2DF developed in 21 (66%) and 11 (34%) waves, respectively. Double ovulations occurred in only one of the waves with 2DF. In 8/11 waves with 2DF, a second deviation occurred between F1 and F2 on 2.5 ± 0.4 days after the first deviation. On day 0, 1DF and 2DF waves were similar in number of days after ovulation, number of follicles, difference in diameter between F1 and F2, and plasma concentrations of LH, estradiol and immunoreactive inhibin. The interval from maximum FSH concentration to day 0 was longer (p < 0.05) and FSH concentration was lower (p < 0.05) on days -1 to 4 in the 2DF group. The similarities on day 0 in the characteristics of 1DF and 2DF waves despite the differences in the declining portions of the FSH profile indicated that a specific day of the FSH decline or a specific concentration were not factors in initiating deviation. Unlike reported results in heifers, the results in mares did not indicate a hormonal basis for the development of 2DF or two deviations.     

Environmental risk assessment of a metal-contaminated area in the Tropics. Tier I: screening phase

Purpose  

The present study presents data on the screening phase (tier 1) of a site-specific ecological risk assessment in a former smelter area heavily contaminated with metals (Santo Amaro, Bahia, Brazil). Joining information from three lines of evidence (LoE), chemical, ecotoxicological, and ecological, integrated risk values were calculated to rank sites within the area and identify those that may need further investigation in tier 2.