A Review of Methods for Measuring the Surface Area of Stream Substrates

Surface area measurement is a common component of benthic research, especially in the quantification of chlorophyll. Multiple techniques are available and 10 are described: artificial substrates, area-specific sampling, geometric approximation, stone shape equations, foil wrapping, grids, stamps, wetted layer, particle layer, and planar area measurement. A literature search of 130 papers indicated the most common methods: using artificial substrates of known area, subsampling a specific area using a template or sampler, measuring stone dimensions and using an equation to derive area, and using the weight of foil wrapped on stones. Methods were compared using spheres of known area, smooth and rough granite stones, and plastic macrophytes. Most methods produced highly correlated measurements and accurately estimated surface area. The wetted layer method was sensitive to stone roughness and plant complexity, but may overestimate the area of complex surfaces. Replication of one method by 10 biologists indicated that individual differences in technique can affect surface area values. Factors to consider in choosing an appropriate method include ease of use, characteristics of the substrates (e.g., porosity and flexibility), fineness of scale in measuring area, and whether methods must be field-based or can include laboratory techniques.     

喀斯特生态脆弱区典型小生境土壤团聚体稳定性比较研究

为探究喀斯特小生境类型对土壤团聚体稳定性影响,揭示小生境土壤团聚体主要失稳机制,选取研究区内石缝、石沟、石槽、石土面和土面5种典型小生境为研究对象,采用干筛法、Elliott湿筛法和Le Bissonnais法测定土壤团聚体稳定性。结果表明：湿筛后,团聚体分布以水稳性团聚体（WR_>0.25）为主,含量在81.26%以上,团聚体破坏率（PAD）介于8.93%-17.39%之间,平均重量直径（MWD）在1.94-2.85 mm间,均小于干筛,团聚体稳定性表现为石槽最好,土面最差,石土面次之。LB法处理后,MWD值变化趋势为慢速湿润（SW） > 预湿润后扰动（WS） > 快速湿润（FW）,即小生境土壤团聚体最大破坏机制为大雨或暴雨时快速湿润FW产生的消散作用,团聚体稳定性同样以石槽最好,土面最差,石土面次之。相关性分析显示,LB法测定的MWD均与湿筛法的WR_>0.25呈显著正相关,与PAD呈显著负相关,即LB法和湿筛法具有良好的相关性,LB法用于测定喀斯特地区土壤团聚体稳定性是可行的（P<0.05）。LB法FW处理的MWD值与有机质呈显著正相关,即有机质对团聚体稳定性有重要影响;全氮、全磷、全钾与WR_>0.25、SW处理的MWD值呈显著正相关,与PAD呈显著负相关,即稳定的团粒结构对养分蓄积有正向效应（P<0.05）。综合不同测定方法的结果表明,土面、石土面易造成土壤流失,应加强雨季对喀斯特生态脆弱区土面、石土面小生境的防护。     

Response to drought stress of nitrogen fixation (acetylene reduction) rates by field-grown soybeans

The effects of drought stress on soybean nodule conductance and the maximum rate of acetylene reduction were studied with in situ experiments performed during two seasons and under differing field conditions. In both years drought resulted in decreased nodule conductances which could be detected as early as three days after water was withheld. The maximum rate of acetylene reduction was also decreased by drought and was highly correlated with nodule conductance (r = 0.95). Since nodule conductance is equal to the nodule surface area times the permeability, the relationship of these variables to both whole-plant and unit-nodule nitrogenase activity was explored. Drought stress resulted in a decrease in nodule gas permeability followed by decreases in nodule surface area when drought was prolonged. Under all conditions studied acetylene reduction on a unit-nodule surface area basis was highly correlated with nodule gas permeability (r = 0.92). A short-term oxygen enrichment study demonstrated nodule gas permeability may limit oxygen flux into both drought-stressed and well-watered nodules of these field-grown soybeans.     

Life history features of some macroinvertebrates in a French Polynesian stream

The invertebrate fauna of the Opunohu River catchment in Moorea, French Polynesia, studied 1988–1989, was numerically dominated by four species of neritid snails, one species of thiarid snail, two species of atyid shrimp, two species of palaemonid shrimp, and ten species of coenagrionid, chironomid, and simuliid insect larvae. Numbers of egg capsules of neritid snails were higher in riffles (maximum x density > 10,000/m² surface area) than pools, were highest in riffles in September and pools in August, and were lowest in both habitats in March and December. The snail Neritina canalis Lamarck and the shrimp Atyoida pilipes Newport, Caridina weberi DeMan, Macrobrachium lar Fabricius, and Macrobrachium australe Guerin‐Menévílle are diadromous: they enter freshwater as juveniles and migrate upstream; their larval offspring return to the ocean for growth and development. Ovigerous females of A. pilipes and M. lar were mainly found in austral fall; ovigerous females of C. weberi and M. australe were found in both austral fall and spring. Ovigerous females were the largest individuals of each shrimp species collected. Mean size of N. canalis, A. pilipes, C. weberi, and M. lar was generally larger in upstream than downstream reaches; no such difference was found for the non‐diadromous thiarid snail Melanoides tuberculata Müller. Coenagrionid, chironomid, and simuliid insect larvae have multiple cohort populations but at least one simuliid species occurs as a single cohort. Downstream habitat alteration may strongly influence the distribution of diadromous species.     

Characterization of benthic microhabitat: An experimental system for aquatic insects

An experimental system used to determine microhabitat current velocity and microhabitat selection by aquatic insects is described. The experimental system includes a microvelocity probe and a hydraulically calibrated artificial substrate. A thermistor velocity probe detects flow velocities to 0.5 m s^–1 near the surface of substrates at locations inhabited by aquatic insects. The artificial substrate was designed to provide two major habitat types, highly turbulent vortex areas and regions with unidirectional, near laminar flow. Substrate calibration and microhabitat characteristics of the substrates are demonstrated. Experimental studies of Simulium sp. location on substrates indicated that while simuliid larvae are characteristic of lotic, erosional habitats, actual microhabitats selected are governed by substantially lower flow velocity.     

Effect of peak pressure and pressure gradient on subsurface shear stresses in the neuropathic foot

The pressure distribution on the plantar surface of the foot may provide insights into the stresses within the subsurface tissues of patients with diabetes mellitus and peripheral neuropathy (PN) who are at risk for skin breakdown. The purposes of this study were to (1) estimate the stress distribution in the subsurface soft tissue from a measured surface pressure distribution and determine any differences between values in the forefoot and rearfoot, and (2) determine the relationship between maximum shear stress (MSS) (magnitude and depth) and characteristics of the pressure distribution. The measured in-shoe pressure distributions during walking characterized by the peak plantar pressure and maximum pressure gradient on the plantar surface of the feet for 20 subjects with diabetes, PN and history of a mid foot or forefoot plantar ulcer were analyzed. The effects of peak pressure and maximum pressure gradient at the peak pressure location on the stress components in the subsurface soft tissue were studied using a potential function method to estimate the subsurface tissue stress. The calculated MSSs are larger in magnitude and located closer to the surface in the forefoot, where most skin breakdown occurs, compared to the rearfoot. In addition, the MSS (magnitude and depth) is highly correlated with the pressure gradient (r=-0.77 & 0.61) and the peak pressure (r=-0.61 & 0.91). The peak pressure and the maximum pressure gradient obtained from the surface pressure distribution appear to be important variables to identify where MSSs are located in the subsurface tissues on the plantar foot that may lead to skin break down.     

Patterns of species richness for blackflies (Diptera: Simuliidae) in the Nearctic and Neotropical regions

Abstract.  1. Patterns of simuliid species richness were examined over a variety of scales at 532 stream sites in the Nearctic (394) and Neotropical (138) regions. In Nearctic streams, species richness of immature blackflies both within and across ecoregions and over two seasons was examined. Stream variables at each site included seston, width, depth, velocity, discharge, conductivity, pH, dissolved oxygen, water temperature, dominant streambed-particle size, canopy cover, and riparian vegetation. These variables were subjected to a principal component analysis and derived principal components were related back to richness, using regression analysis. At the level of the stream reach, richness was not highly correlated with single-point measurements of stream conditions.
2. Using data from both Nearctic and Neotropical sites, the effect of regional richness on local richness was examined. As regional richness increased, local diversity reached an asymptote in which further increases in regional richness were not matched by increases in local richness. Hence, simuliid communities are best described as saturated (type II) communities, consistent with the current view of lotic communities as non-equilibrium systems.
3. The well-established pattern of greater species richness in tropical regions was not observed in this study. To the contrary, blackfly richness is higher in temperate streams than in tropical streams at both local and regional scales.     

Mermithid Parasitism of Black Flies (Diptera: Simuliidae)

Mermithid nematodes are common parasites of black flies and play a significant role in the natural regulation of these medically important insects. Infection levels tend to he moderate and perennial, with epizootics rare and highly localized. Mermithid parasitism almost invariably results in the death of the black fly, and thus considerable attention has focused on the potential of these nematodes as biocontrol agents. Early instar black fly larvae appear most susceptible to infection, and integumental penetration hy mermithid preparasites is the only known mode of entry. Postparasitic nematodes typically emerge before host pupation. However, carryover of parasitism into adult simuliids is an important mechanism for local dispersal and recolonization of upstream areas. Following emergence, the mermithids molt to the adult stage. Copulation ensues, the females then laying eggs which eventually give rise to the next generation of infective preparasites. The number of described species is conservatively estimated at 35-40, with most species within the genera Mesomermis, Gastromermis, and Isomermis. The taxonomy of this group of mermithids is a challenging and little explored area. Host-specificity statements, therefore, must be made cautiously because of these systematic problems and others within the Simuliidae. In most instances, temporal and spatial factors limit the host range of these mermithids among simuliid species. Differential susceptibilities anmng larvae concurrently present within the same microhabitat probably reflect varying degrees of host attractiveness and behavioral-physiological resistance. Effects of parasitism on the host may include prevention of metamorphosis, sterility, intersexual development, and behavior modification. Evaluation of the technical feasibility of mermithid control of black flies has been stymied by the limitations of current inoculum-production technology. Continued advances in in vivo and in vitro culture methods are required to accelerate the research process.     

Microgeographical variation in shell size of the land snail Chondrina clienta

Microgeographical variation in shell morphology of the rock-dwelling land snail Chondrina clienta , collected from 30 sites within an area of 0.5 km² on the island of Öland, Sweden, was examined in relation to its own population density and that of a potential competitor (the land snail Balea perversa ) and to environmental factors. Dispersal of marked individuals averaged 83 cm per year within a stone pile and 291 cm in an area of exposed bedrock. Local population density of active C. clienta ranged from 5 to 794 individuals per m². Shell characters were highly intercorrelated, both within and between populations. Principal component analysis revealed that most of the interpopulational variation could be expressed by the single character of shell height, which ranged from 5.54 to 6.94 mm. In all populations, snails of a given size had the same whorl number. Shell size was not influenced by habitat type (exposed rock surface, stone pile or stone wall) or proportion of calcareous stones within habitat. It was, however, negatively correlated with local population density, indicating intraspecific competition, and positively correlated with the degree of plant cover within the habitat. Analysis of variance revealed additionally a density effect of B. perversa on shell size in C. clienta , probably as a result of interspecific competition. Breeding experiments using C. clienta from different sites and carried out under unifrom conditions caused most of the phenotypic variation to disappear, demonstrating the high phenotypic plasticity of the species.     

An improved technique for estimating pectoral muscle protein condition from body measurements of live gulls

Body measurements, which could be taken from live birds, were used to estimate total pectoral muscle protein in Lesser Black-backed Gulls Larus fuscus. The maximum cross-sectional area of the flight muscles was measured from the profile of the muscle surface over the keel, and this was used in conjunction with the length of the flight muscle to estimate muscle volume. The estimate of muscle volume was then used with fresh body weight to estimate total flight muscle protein. A highly significant correlation was found between the estimated values and actual pectoral muscle protein mass determined by carcass analysis. The model developed from the source group was then validated using a second independent sample, in which flight muscle protein was estimated from the model. Carcass analysis again demonstrated a good correlation between estimated and actual total protein. Different methods of controlling for body-size to calculate protein condition from measures of total protein were considered. The technique described here provides a simple and reliable method of estimating pectoral muscle protein condition in live gulls which could be applied to studies of body condition in other species.     

北京市主城区不透水面时空演变及其热环境效应研究

城市不透水面是表征城市化进程的重要指标,开展城市不透水面研究对生态环境监测及城市建设规划具有重要意义.以北京市主城区为研究区,基于Landsat影像采用支持向量机(SVM)和线性光谱混合分解模型(LSMM)相结合的方法提取研究区2002年、2009年和2017年三期不透水面;同时采用辐射传输方程法反演研究区地表温度,分...     

A 3D modeling method to calculate the surface areas of coral branches

The quantification of physiological and biochemical parameters in coral branches require normalization to a stable factor, such as the tissue biomass or surface area. Three dimensional (3D) animation software (Gmax^®) was evaluated for estimating the surface area of simple coral branches. The software was highly predictive of the known surface areas of small (20–60 mm long) plastic rods and cones (r ² > 0.99), and of small (30–60 mm) Acropora millepora branches (r ² = 0.98) whose surface area had been obtained using the traditional wax-weight method. Two normalization parameters, 3D modeled surface area and tissue biomass (measured as protein), were then compared for A. millepora branches collected in summer and winter. In winter, protein and surface area were correlated (r ² > 0.61), but not in summer, indicating that choice of normalizing parameter will influence the outcome of experimental analyses.     

Biting behaviour and potential vector status of anthropophilic blackflies in a new focus of human onchocerciasis at Minaçu, central Brazil

Monthly collections were made of man‐biting female blackflies: Simulium auripellitum Enderlein, S. guianense Wise, S. minusculum Lutz and S. nigrimanum Macquart (Diptera: Simuliidae) from four catching stations in the newly discovered focus of human onchocerciasis at Minaçu (13°35′ S 48°18′ W), 300 km north of Brasília in Goiás State. These provided baseline data on biting habits, population density and seasonal prevalence during the year before completion of the Serra da Mesa hydroelectric dam on the Rio Tocantins near Minaçu, in a project investigating the effect of dam construction on onchocerciasis transmission in the area. All four simuliid species were most abundant during the dry season, and only bit in low numbers (S. auripellitum S.minusculum, S. nigrimanum) or were absent (S. guianense) in the wet season. Simulium minusculum was the predominant species at all catching stations, being particularly abundant by the large River Tocantins. The other three species were mainly associated with smaller rivers. In the dry season, biting rhythms of S. minusculum varied with catching site, while S. nigrimanum showed peaks of activity in early morning and during the afternoon. Experimental infection with Onchocerca volvulus (Leuckart) (Nematoda: Onchocercidae), from a human volunteer, showed that this parasite could develop fully in the four simuliid species, which are all considered to be potential vectors in the area.     

Accounting for radiotelemetry signal flux in triangulation point estimation

Triangulation by radiotelemetry is a method commonly used to estimate locations of wildlife. Despite the importance of the accuracy of resulting location estimates, there has been little development and comparison of alternative methods for point-location estimation for 25 years. Most methods assume that signal transmissions as they are received are consistent, but signal heterogeneity and fluxing is common. Using data from a beacon study, we determined that a subjective ranking of confidence in the accuracy of a signal was correlated with absolute bearing error. Using this factor and the distance from a telemetry station to the error triangle incenter, we developed an algorithm to place a weighted point-location estimate in relative proximity to each error triangle leg. We have termed this the weighted-incenter method. Despite previous findings that the major confidence ellipse axis of Lenth’s maximum likelihood estimator (MLE) correlated best to linear distance error, our beacon test data indicated that total bearing angle difference was the best single predictor of linear error with an optimal total angle of about 100°. The new and intuitive weighted-incenter method offered some improvement over previous methods such as the MLE estimator, but only with suboptimal angle bearings that may be common in field studies. By using a MATLAB function to produce data for site-specific regression analyses, one can determine which method should produce the more accurate point-location estimate for each triangulation observation. Further significance of this study for field biologists is discussed.     

Evaluating Methods for Counting Cryptic Carnivores

ABSTRACT Numerous techniques have been proposed to estimate carnivore abundance and density, but few have been validated against populations of known size. We used a density estimate established by intensive monitoring of a population of radiotagged leopards (Panthera pardus) with a detection probability of 1.0 to evaluate efficacy of track counts and camera-trap surveys as population estimators. We calculated densities from track counts using 2 methods and compared performance of 10 methods for calculating the effectively sampled area for camera-trapping data. Compared to our reference density (7.33 ± 0.44 leopards/100 km²), camera-trapping generally produced more accurate but less precise estimates than did track counts. The most accurate result (6.97 ± 1.88 leopards/100 km²) came from camera-trap data with a sampled area buffered by a boundary strip representing the mean maximum distance moved by leopards outside the survey area (MMDMOSA) established by telemetry. However, contrary to recent suggestions, the traditional method of using half the mean maximum distance moved from photographic recaptures did not result in gross overestimates of population density (6.56 ± 1.92 leopards/100 km²) but rather displayed the next best performance after MMDMOSA. The only track-count method comparable to reference density employed a capture-recapture framework applied to data when individuals were identified from their tracks (6.45 ± 1.43 leopards/100 km²) but the underlying assumptions of this technique limit more widespread application. Our results demonstrate that if applied correctly, camera-trap surveys represent the best balance of rigor and cost-effectiveness for estimating abundance and density of cryptic carnivore species that can be identified individually.     

An assessment of biological interactions in an epilithic stream community using time-lapse cinematography

In situ time-lapse cinematography was used to record and enumerate behavioral interactions between members of an epilithic insect community in a small Michigan (U.S.A.)trout stream. 145 interactions were observed during 78 hours of filming. Most of these (98%) involved simuliid larvae. Interactions between simuliid larvae occurred at about the same frequency as interactions between simuliids and other taxa. However, interactions between simuliid larvae were less likely to lead to emigration than were interactions between blackflies and other groups. Significant short-term fluctuations of faunal density on filmed surfaces were also observed. The causes of these fluctuations appeared varied. The results of a preliminary assessment of interactions and the usefulness of this technique are discussed.     

Genetic parameters of a biological lactation model: early lactation and secretion rate traits of dairy heifers

Early lactation parameters are difficult to estimate from commercial dairy records due to the small number of records available before the peak of production. A biological model of lactation was used with weekly milk records from a single Holstein herd to estimate these early lactation parameters and the secretion rate of milk from the average cell throughout lactation. A genetic analysis of the lactation curve parameters, calculated curve characteristics and secretion rate traits was undertaken. Early lactation traits were found to have little genetic variation and effectively zero heritability. Secretion rate traits for milk, protein, lactose and water were all moderately heritable and highly genetically correlated (>0.87) but fat secretion rate had lower genetic correlations with the other secretion rates. A similar pattern of correlations was seen between total lactation yield traits for fat, protein, lactose and water. The genetic correlations between the lactation curve traits and the secretion rate traits were calculated. Total milk yield, peak yield and maximum secretion potential were all highly correlated with milk, lactose and water secretion rates but less so with fat and protein secretion rates. In particular, fat secretion rate had a moderate to low genetic correlation with these lactation curve traits. Persistency of lactation was highly correlated with fat and protein secretion rates, more persistent lactations being associated with lower rates of secretion of these milk components. Similar levels of heritability were found, where trait genetic parameters were directly equivalent to those derived from the same dataset by random regression methods. However, by using a biological model of lactation to analyse lactation traits new insights into the biology of lactation are possible and ways to select cows on a range of lactation traits may be achieved.     

Wernicke's area homologue in chimpanzees (Pan troglodytes) and its relation to the appearance of modern human language

Human language is distinctive compared with the communication systems of other species. Yet, several questions concerning its emergence and evolution remain unresolved. As a means of evaluating the neuroanatomical changes relevant to language that accompanied divergence from the last common ancestor of chimpanzees, bonobos and humans, we defined the cytoarchitectonic boundaries of area Tpt, a component of Wernicke''s area, in 12 common chimpanzee brains and used design-based stereologic methods to estimate regional volumes, total neuron number and neuron density. In addition, we created a probabilistic map of the location of area Tpt in a template chimpanzee brain coordinate space. Our results show that chimpanzees display significant population-level leftward asymmetry of area Tpt in terms of neuron number, with volume asymmetry approaching significance. Furthermore, asymmetry in the number of neurons in area Tpt was positively correlated with asymmetry of neuron numbers in Brodmann''s area 45, a component of Broca''s frontal language region. Our findings support the conclusion that leftward asymmetry of Wernicke''s area originated prior to the appearance of modern human language and before our divergence from the last common ancestor. Moreover, this study provides the first evidence of covariance between asymmetry of anterior and posterior cortical regions that in humans are important to language and other higher order cognitive functions.     

Fine Structure of Oocyst Transformation and the Sporozoites of Leucocytozoon dubreuili*

SYNOPSIS. The sporogonic stages of Leucocytozoon dubreuili in the midgut and salivary glands of the simuliid vectors was studied by electron microscopy. Young uninucleate oocysts have a pellicle that initially resembles that of the ookinetc. Numerous electron-dense bodies and microtubules in the peripheral cytoplasm may be involved in the formation of the cyst wall. The dense bodies appear to give rise to the amorphous material of the wall. The tubules which run circumferentially beneath the oocyst's boundary probably serve as a skeletal support for the cell surface during deposition of the wall material. A subcapsular “space” which provides area for expansion of the developing sporozoites is formed in early multinucleate oocysts. The subcapsular “space” appears to be formed through a condensation of the peripheral cytoplasm, resulting in an osmotic gradient across the oocyst's limiting membrane. Consequently water diffuses out, creating a fluid-filled space. Sporozoite formation begins with localized thickenings on the oocyst's limiting membrane. Subsequent extension of the thickened regions into the subcapsular “space” marks the onset of sporozoite budding. The process is highly synchronized, and culminates with the production of up to 150 sporozoites about the sporoblastoid body. The structure of sporozoites from mature oocysts and of the salivary glands of the vector is basically similar, although salivary gland sporozoites are more elongate and have numerous electron-dense micronemes. The paired rhoptries in the latter sporozoites are more elongate and uniformly electron-dense than in oocyst sporozoites.     

Durability of Simuliid Silk Pads (Simuliidae,Diptera)

A central aspect of simuliid adaption to life in moving water is a silky secretion which they produce in their salivary glands. This secretion is spread on the substrate surface thereby enabling adhesion of the posterior abdominal hooks of the larvae to the substrate surface. Therefore, silk pads are a prerequisit for simuliid filter‐feeding as well as any kind of locomotive activity. If silk pad adhesion is weak, larvae risk drifting off, either directly or during locomotion. Properties of the adhesive (=silk) as well as the substrate surface may cause weak adhesion. A specialist such as S. noelleri which has little chance of surviving after drifting off its lake outlet habitat, should have adaptations to reduce this risk. Such an adaptation could be very durable silk pads, giving larvae the chance to be safely attached for a relatively long time. In this study larval silk pads of S. ornatum and S. noelleri were stained using Giemsa's staining procedures. Changes in silk pad structure and traces of rot after 2–33 days of exposure to stream water were recorded and compared. Silk pads of S. ornatum and S. noelleri showed differences which indicate differences in ageing processes and biochemistry of this secretion.