首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
When juvenile praying mantids (Tenodera sinensis)were exposed to unpalatable prey (the milkweed bug Oncopeltus fasciatus),they attacked, sampled, and then usually rejected the prey. About 70% of the handling time was spent feeding. When offered a second milkweed bug, the mantids usually attacked the prey. However, the overall time required for the mantids to sample, recognize, and then reject the unpalatable prey decreased by half. The proportion of handling time that was spent feeding remained the same as in the first encounter. In contrast, when the second prey individuals encountered by mantids were Drosophila melanogaster,the flies were completely consumed and the proportion of handling time that was spent feeding significantly increased. When praying mantids were exposed to the milkweed bugs for the first time, up to 33% of the bugs survived attack by the mantids. Survival of milkweed bugs increased to 55% when mantids had been previously exposed to the bugs. In contrast, flies that were caught never survived.  相似文献   

2.
To examine the proper margin for breast conservative surgery in Chinese women population. 40 breast cancer specimens were collected and each sample was dissected into several groups: primary tumor group, 1 cm paracarcinoma, 2 cm paracarcinoma, 3 cm paracarcinoma and excessive 3 cm paracarcinoma groups. The immunohistochemistry staining was performed to measure the expression levels of proliferating cell nuclear antigen (PCNA), c-erbB-2, p53, estrogen receptor (ER) and progesterone receptor (PR). The gene expressions of PCNA, c-erbB-2, and p53 gradually decreased with the increased distance from primary tumor (P < 0.05). The 1 and 2 cm paracarcinoma group (no differences between the two, P > 0.05) showed higher risk factors (c-erbB-2, p53) than the 3 cm and excessive 3 cm paracarcinoma groups (P < 0.05). The expression of PCNA, ER, and PR showed no correlation with cancer progression (P > 0.05). Beyond the paracarcinoma 2 cm distance, the tissues showed significant decreases in tumor gene expression, which could represent the appropriate region for breast conservative surgery.  相似文献   

3.
Males that search widely for females and perform conspicuous courtship displays run a high risk of being detected by their predators. Therefore, gains in reproductive success might be offset by increased mortality due to predation. Male brush‐legged wolf spiders (Schizocosa ocreata) with larger decorative traits (foreleg tufts) are preferred by females as mates, but are more readily detected by predators. However, predation risk may also be influenced by the interaction between components of signals and the environment in which signaling occurs. Courting male spiders were readily accepted as prey by a sympatric predator, the American toad (Anaxyrus americanus). We used video playback to tease apart the interactive effect between visual signals and the signaling environment on the ability of toads to detect courting spiders as a function of distance, background contrast, the presence or absence of male foreleg tufts, and behavioral activity. The response of toads to video sequences of male spiders was similar to their response to live male spiders. Toad response varied over distance toward spiders displayed against high contrast (sunny) vs. low contrast (shaded) backgrounds. Beyond 30 cm, more toads detected courting male spiders against light, ‘sunny’ backgrounds and detected them faster when compared to the same spider stimulus against darker, ‘shady’ backgrounds. In choice tests, toads oriented more often toward courting males with leg tufts than those without. Toad responses also varied with male spider behavior in that only videos of moving males were attacked. Latency to orient and detection by toads was significantly greater for walking males than courting males, and this effect was most evident at distances between 30 cm and 50 cm. Results supported that courting wolf spiders are at significant risk of predation by visually acute predators. Distance, background contrast, and the presence of foreleg decorations influence detection probability. Thus, the same complex visual signals that make males conspicuous and are preferred by females can make males more vulnerable as prey to toads.  相似文献   

4.
Recently, populations of Castanopsis cuspidata have often expanded into secondary forests in western Japan. To determine the establishment processes of this species, we analyzed its spatial distribution in a secondary forest dominated by Quercus variabilis and Quercus serrata that is located adjacent to a stand dominated by C. cuspidata. Saplings, defined as ≥30 cm stem length (SL) and <5 cm diameter at breast height (DBH), were abundant and their size distribution was inversely J-shaped, indicating continuous recruitment. Although seedlings (SL < 30 cm) and small saplings (30 ≤ SL < 50 cm) of C. cuspidata were aggregated near flowering trees of this species, some were found ≥40 m from the nearest adults, suggesting that there is animal-aided dispersal of acorns. The distribution of larger-sized individuals (≥100 cm SL) of C. cuspidata was unrelated to distance from the nearest flowering C. cuspidata or dominant Quercus species (≥5 cm DBH), but was associated with dead Pinus densiflora trees, which were abundant at the site. Thus, the establishment of C. cuspidata in this forest is controlled mainly by two factors, viz. patterns of acorn dispersal by animals, and forest disturbance regime (i.e., deaths of pine trees).  相似文献   

5.
Restriction site‐associated DNA sequencing (RAD‐seq) was used to illuminate the genetic relationships among Eriobotrya species. The raw data were filtered, and 221 million clean reads were used for further analysis. A total of 1,983,332 SNPs were obtained from 23 Eriobotrya species and two relative genera. We obtained similar results by neighbor‐joining and maximum likelihood phylogenetic trees. All Eriobotrya plants grouped together into a big clade, and two out‐groups clustered together into a single or separate clade. Chinese and Vietnam accessions were distributed throughout the dendrogram. There was nonsignificant correlation between genotype and geographical distance. However, clustering results were correlated with leaf size to some extent. The Eriobotrya species could be divided into following three groups based on leaf size and phylogenetic analysis: group A and group B comprised of small leaves with <10 cm length except E. stipularis (16.76 cm), and group C can be further divided into two subgroups, which contained medium‐size leaves with a leaf length ranged from 10 to 20 cm and a leaf length bigger than 20 cm.  相似文献   

6.
Root morphological adaptation is an important mechanism for wetland plants to adapt to environmental conditions. The objective of this study was to investigate the impact of water depth on biomass allocation and root morphology (including root mean diameter, root length, root surface area and root volume) of a wetland plant species, Juncellus serotinus (Cyperaceae). Four levels of water depth were chosen: 10, 30, 50 and 70 cm. Due to the enormous root system, and for easy observation, five groups were used according to the distance from the rhizome: 0–5, 5–10, 10–15, 15–20 and longer than 20 cm (> 20 cm). Results showed that with increasing water depth plant total biomass and root biomass decreased significantly (p < 0.05), and that biomass was mainly allocated to shoots resulting in decreased root to shoot ratio. Root morphology parameters also changed significantly with increasing water depth (p < 0.05). Root mean diameter in all treatments and all other root morphology parameters decreased with increasing distance from the rhizome, while maximum root length, root surface area and root volume in 10 and 30 cm occurred between 5 and 15 cm from the rhizome. The results indicate that shallow water (less than 30 cm in depth) is favorable for the development of J. serotinus root system, and that root morphological characteristics shift with increasing distance from the rhizome.  相似文献   

7.
The objective of this study was to determine the influence of distance from surface water on riparian woodland communities in the Okavango Delta. Vegetation sampling was conducted in seven sites within the Okavango Delta in 20 m × 10 m belted plots placed perpendicular to the river bank. The plots were placed at 0–10 m, 10–20 m, 20–30 m, 30–40 m and 40–50 m distance classes increasing away from the river bank. Tree height, basal area, species richness, canopy cover and diversity were determined for each distance class. Indicator species analysis was used to determine the characteristic species at each distance class. Single‐factor ANOVA and Tukey post hoc analysis were used to compare species diversity, mean tree height, cover and basal area between distance classes. Correlation between distance from surface water and vegetation parameters was sought using Spearman regression analysis. All parameters except for species richness varied significantly (< 0.05) along distance from surface water. Distance from surface water was positively correlated all vegetation parameters except for mean species richness/plot. These results show that distance from surface water influences riparian plant community composition and distribution in the Okavango Delta. This implies that riparian plant species can be indicators of long‐term hydrologic conditions in the Delta.  相似文献   

8.
Despite the obvious importance of roots to agro‐ecosystem functioning, few studies have attempted to examine the effects of warming on root biomass and distribution, especially under different tillage systems. In this study, we performed a field warming experiment using infrared heaters on winter wheat, in long‐term conventional tillage and no‐tillage plots, to determine the responses of root biomass and distribution to warming. Soil monoliths were collected from three soil depths (0–10, 10–20, and 20–30 cm). Results showed that root biomass was noticeably increased under both till and no‐till tillage systems (12.1% and 12.9% in 2011, and 9.9% and 14.5% in 2013, in the two tillage systems, respectively) in the 0–30 cm depth, associated with a similar increase in shoot biomass. However, warming‐induced root biomass increases occurred in the deeper soil layers (i.e., 10–20 and 20–30 cm) in till, while the increase in no‐till was focused in the surface layer (0–10 cm). Differences in the warming‐induced increases in root biomass between till and no‐till were positively correlated with the differences in soil total nitrogen (R2 = .863, < .001) and soil bulk density (R2 = .853, < .001). Knowledge of the distribution of wheat root in response to warming should help manage nutrient application and cycling of soil C‐N pools under anticipated climate change conditions.  相似文献   

9.
Specimens of the trace fossil Rhizocorallium isp. with retrusive limbs occur in 10–20-cm-thick composite beds: the bottom layers contain abundant Planolites and Thalassinoides trace fossils, and the top layers are built of horizontally bedded pelitic limestone and contain less bioturbational structures. The first specimens of Rhizocorallium isp. occur just 2–3 cm above the lower surfaces of the top layers. The horizontal protrusive sections are 1 cm high and 1 cm wide. At some sites, the horizontal tunnels end, and the limbs become first obliquely retrusive (45°) at a distance of 1.5–2.5 cm, and then vertically retrusive at a distance of 4–6 cm, or at once vertically retrusive at a similar distance. They reach to the upper surfaces of the top layers. These composite beds with unusual Rhizocorallium mark successive stages of distal tempestite sedimentation. The erosional events are recorded as uneven bases and a lack of Rhizocorallium, which suggests erosion to approx. 10 cm deep. The lower parts of the top layers record deposition of lime mud from a powerful flow. The protrusive sections of Rhizocorallium record relatively quiet periods resulting from significantly decreased sedimentation. The successive retrusive sections provide evidence that the quiet conditions suddenly came to an end, and that sedimentation was reactivated or accelerated. The last retrusive limbs of Rhizocorallium isp. mark the border of the storm event and the next erosion event. The composition of the fecal pellets shows that these burrowing animals were deposit-feeders, fast enough to find a sufficient amount of food, and also fast enough to escape being buried.  相似文献   

10.
Biodegradation of glyphosate in sod-podzol soil by both the indigenous micro flora and the introduced strain Ochrobactrum anthropi GPK 3 was studied with respect to its sorption and mobility. The experiments were carried out in columns simulating the vertical soil profile. Soil samples studied were taken from soil horizons 0–10, 10–20, and 20–30 cm deep. It was found out that the most of the herbicide (up to 84%) was adsorbed by soil during the first 24 h; the rest (16%) remained in the soluble fraction. The adsorbed glyphosate was completely extractable by alkali. No irreversible binding of glyphosate was observed. By the end of the experiment (21st day), glyphosate was only found in extractable fractions. The comparison of the effect of the introduced O. anthropi GPK 3 and indigenous microbial community on the total toxicant content (both soluble and absorbed) in the upper 10 cm soil layer showed its reduction by 42% (21 mg/kg soil) and 10–12% (5 mg/kg soil), respectively. Simultaneously, 14–18% glyphosate moved to a lower 10–20 cm layer. Watering (that simulated rainfall) resulted in a 20% increase of its content at this depth; 6–8% of herbicide was further washed down to the 20–30 cm layer. The glyphosate mobility down the soil profile reduced its density in the upper layer, where it was available for biodegradation, and resulted in its concentration in lower horizons characterized by the absence (or low level) of biodegradative processes. It was shown for the first time how the herbicide biodegradation in soil can be increased manifold by introduction of the selected strain O. anthropi GPK 3.  相似文献   

11.
The effect of wind speed and distance from the source on the male response of the aphid parasitoid, Aphidius ervi (Hymenoptera: Aphidiidae), to a pheromone source was studied in a wind tunnel. The number of males taking flight, entering the plume and successfully reaching the source, decreased at wind speeds >50 cm/s. Furthermore, the proportion of those attempting upwind flight that fell to the ground increased with increasing wind speed. In contrast, distance from the source had no significant effect on any of the parameters examined. While male flight behavior was significantly reduced at 70 cm/s, some males walked to the source when there was a bridge connecting the pheromone source and the release platform. This suggests that ambulatory behavior could be a significant component of male mate searching in A. ervi when wind conditions are too strong for upwind flight. The possible effects of variation in atmospheric pressure on male flight behavior to the long distance pheromone, as well as to the short distance one, were also investigated. No significant effects of atmospheric pressure were observed. These findings differ significantly from those previously reported for another aphid parasitoid, A. nigripes, and the reasons for such differences are discussed.  相似文献   

12.
To remediate benzene, toluene, ethylbenzene and xylene (BTEX) -contaminated groundwater, a biotreatment process including biostimulation and bioaugmentation was simulated using oxygen-releasing reactive barriers (ORRB) and water with added BTEX in a lab-scale system. The results showed that the capability for BTEX removal decreases in the order of benzene, toluene, p-xylene, ethylbenzene for both added-nitrogen and no-added-nitrogen under BTEX concentrations at 30 mg l−1. The removal efficiencies in ORRB systems were higher in the nitrogen-added condition for biostimulation compared with the no-nitrogen-added condition; moreover, an increased pattern for removal was observed during the bioaugmentation process. The oxygen content was found to be inversely proportional to the distance from the ORRB, as evidenced by observing that the average bacteria densities were two orders higher when located at 15 cm compared with 30 cm from the ORRB. The microbial community structure was similar in both cases of added-nitrogen and the no-added-nitrogen conditions.  相似文献   

13.
14.
The influence of predator exposure on the survival of hatchery red drum, Sciaenops ocellatus was investigated under laboratory conditions. Several prey-capture (attack distance, mean attack velocity, capture time, and gape cycle duration) and anti-predator (reaction distance, response distance, mean velocity, and maximum velocity) performance variables were quantified using high-speed video for juvenile red drum (25–30 mm standard length, L S ) reared with and without predators (pinfish, Lagodon rhomboides). Univariate contrasts of prey-capture events demonstrated that attack distance (mean ± s.e.) was significantly greater in red drum reared with (1.20 ± 0.16 mm) versus without (0.65 ± 0.09 mm) pinfish predators. During anti-predator events, red drum reared with predators had approximately 300% greater reaction distance and 20%–30% greater response distance, mean velocity and maximum velocity versus fish reared without predators; however, these differences were not statistically significant. Following video assessments, a series of mortality experiments were conducted using free-ranging pinfish predators. Mortality rates (Z) ranged from 0.047 to 0.060 (Z/hr/predator) and did not differ significantly among treatments.  相似文献   

15.
To determine the depth of soil at which mated females of the white grub beetle Dasylepida ishigakiensis Niijima et Kinoshita oviposited and their larval offspring stayed in the soil in different seasons, 847 mated female and male adults were released into a caged sugarcane field on Miyako Island. We then excavated this field systematically to collect adults and their larval offspring in the soil once or twice per month from 24 April 2002 to 31 March 2003. Dead females were found between 10 and 50 cm deep in the soil (N = 91), but most frequently in the layer 30–40 cm deep (N = 42; 46.2%). They were recovered more frequently in the soil at the plant foot (N = 73; 80.2%) than in the furrows (N = 18; 19.8%). On the other hand, no male carcass was discovered either in the soil or on the ground surface. The number of larvae discovered in the soil per row was large on 30 April (N = 52.5) and on 5 June (N = 58.3), when they were at the first instar. It decreased rapidly thereafter until 21 August (N = 9.5), when they molted to the second instar, and remained at similar levels through to the following 31 March (N = 8.0), during which they were mostly at the third instar. The larvae were found at various soil depths ranging from 0 to 70 cm, but the majority were found between 10 and 30 cm deep. The last sampling on 31 March indicated that mature larvae moved to a deeper layer for estivation. These results suggested that physical control through rotary tillage before they move to the deeper layer may be effective.  相似文献   

16.
This study characterizes the dynamics of sex reversal in the marbled swamp eel, Synbranchus marmoratus (Osteichthyes: Synbranchidae), a diandric hermaphrodite, within the context of managing species with complex sex allocations. Monthly sampling in Marechal Dutra Reservoir, northeastern Brazil, was conducted using metal eel traps from July, 2013, to June, 2014, during which a total of 288 individuals were captured. Morphological and histological comparisons of gonads identified four sex types: primary males (n = 18), females (n = 197), transitional individuals (n = 30), and secondary males (n = 43). Primary males were smallest, ranging 18–32 cm total length. Females were numerically dominant throughout the 1‐year sampling period, and ranged 20–60 cm. Transitional individuals ranged 32–60 cm, and secondary males ranged 46–74 cm. The otolith‐based age of 52 specimens ranged 0.5 to 5+ year. Primary males were only observed at ages 0.5 and 1, and transitional individuals were only observed at ages 3 and 4 during the female‐to‐secondary‐male transition, supporting the existence of two types of individuals: gonochoristic males and protogynous hermaphrodites. This observation was further supported by histological observations of deteriorating ovarian tissue in transitional individuals. Given the length of time required for individuals to attain secondary male status, this species appears to be particularly vulnerable to over‐exploitation. Comparisons with results from other studies suggest sex allocations and adult size distributions vary substantially within this species’ range, adding complexity to management efforts.  相似文献   

17.
The vertical distribution of Stomoxys spp. was studied in a rainforest area, Ipassa‐Makokou biosphere reserve located in the Ivindo National Park of Gabon. From April to June 2006, Vavoua traps were set out during 15 consecutive days per month at different heights above ground level corresponding to vertical layers of rainforest: 50 cm, 10, 20 and 30 m. Stomoxys calcitrans, S. transvittatus, S. omega, S. niger niger and S. niger bilineatus were more abundant at near ground level (50 cm), whereas abundance of S. xanthomelas was greatest in traps higher (20 and 30 m) in the canopy. Fly abundance was significantly different among vertical layers of the forest (H = 36.91; P < 0.001, ddl = 3), and among species to another (H = 41.11, P < 0.001). Vertical distribution of fly species corroborates feeding behaviour as the identification of blood meal origins showed heterogeneity of feeding hosts. High densities of flies were also observed at 10 m, and most S. inornatus were captured at that level. These results show that Stomoxyine flies in this rainforest are present in all vertical layers, from the ground level to the canopy. Their ubiquity, regarding both their habitats and their hosts, should be taken into account if a vector control strategy is planned in this touristic area.  相似文献   

18.
Length–weight relationship (LWR) parameters were determined for three demersal fish species Nuchequula gerreoides, Scarus scaber and Therapon theraps. The fishes were collected by seine net (the mesh size of wing: 12.70 cm, body: 3.81 cm, cod end: 2.54 cm, and total length of net: 20 m) in eastern region of Java Sea Indonesia during October 2016 – March 2017. The total length of these species (14.3 cm for N. gerreoides, 24.5 cm for S. scaber and 21.5 cm for T. theraps) were longer than previous studies. The b values of the LWR were 2.967 for N. gerreoides, 3.046 for S. scaber and 3.0475 for T. theraps.  相似文献   

19.
The study of factors influencing the production and development of wild edible mushroom sporocarps is extremely important in the characterization of the fungi life cycle. The main objective of this work is to determine how tree age influences the speed of sporocarp growth of edible ectomycorrhizal fungi Boletus edulis and Lactarius deliciosus in a Pinus sylvestris stand. This study is based on information recorded on a weekly basis every autumn between 1995 and 2008 in a set of permanent plots in Spain. Sporocarps are collected weekly, and as a result, specimens may not have reached their maximum size. The study area is a monospecific P. sylvestris stand. Three age classes were considered: under 30 years, between 31 and 70 years, and over 70 years. Sporocarps of B. edulis and L. deliciosus grow faster in the first age class stands than in the other two, and in the second age class stands, sporocarps are more than 50% smaller. The average weight of the picked B. edulis sporocarps clearly varies in the three age classes considered, with its maximum in the first age class (127 g and 6.8 cm cap diameter), minimum in the second age class (68 g and 4.7 cm cap diameter), and showing a relative maximum in the third (79 g and 4.3 cm cap diameter). L. deliciosus sporocarps are on average larger in the first age class (48 g and 7.4 cm cap diameter), decreasing in the second (20 g and 5.8 cm cap diameter) and also in the third (21 g and 5.3 cm cap diameter). The results show the influence of tree age in speed of sporocarp growth for the two ectomycorrhizal species.  相似文献   

20.
The potato tuberworm, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), is an important pest of solanaceous crops including potato [Solanum tuberosum L. (Solanaceae)]. Recent evidence of survival of the pest in the Columbia Basin of Oregon and Washington, USA, is surprising as potato tuberworm is most commonly a pest in tropical and subtropical regions. Potato tuberworm was studied in a manipulative experiment to determine how stage (egg, larva, and pupa) and soil depth affected the potential for winter survival. In early January 2007, eggs, tubers infested with larvae, and pupae were placed in the soil at 6, 10, and 20 cm depths, or left on the soil surface. Each potato tuberworm life stage was sampled at 7–17‐day intervals for 90 days and survival was estimated at each time period. Eggs survived up to 54 days with the greatest survival observed at 6‐cm soil depth and the lowest survival on the soil surface. However, egg survival was significantly reduced after 1 month of exposure to winter conditions. Larvae were able to survive up to 30 days with the greatest survival observed at 20‐cm soil depth. Tubers at the surface and buried at 6 cm were frozen; thus, no larval survival was recorded. The pupal stage showed a greater tolerance to winter conditions than the egg or larval stages, surviving up to 91 days of exposure. These results suggest that the pupal stage is probably the stage most likely to survive winter conditions in the northwestern USA.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号