Experimental Boxes Research Articles

The Impact of Spectral Composition of White LEDs on Spinach (Spinacia oleracea) Growth and Development

Light-emitting diodes (LED) are a promising light source for the cultivation of edible vegetables in greenhouses. The spectral radiation of the light sources has an impact on plants physiological parameters, as well as on morphological features. In this study the growth of spinach plants has been carried out in experimental boxes under two white LED treatments having different correlate color temperature (CCT): the cold lighting (CL) corresponded to 6500 K, while the warm lighting (WL) to 3000 K. The work was aimed to investigate the influence of the two light spectra on plant development and comparing the results. Results showed that the different lighting treatments impact differently on plant development and on growth parameters.

Nest-mediated seed dispersal

Many plant seeds travel on the wind and through animal ingestion or adhesion; however, an overlooked dispersal mode may lurk within those dispersal modes. Viable seeds may remain attached or embedded within materials birds gather for nest building. Our objective was to determine if birds inadvertently transport seeds when they forage for plant materials to build, insulate, and line nests. We also hypothesized that nest-mediated dispersal might be particularly useful for plants that use mating systems with self-fertilized seeds embedded in their stems. We gathered bird nests in temperate forests and fields in eastern North America and germinated the plant material. We also employed experimental nest boxes and performed nest dissections to rule out airborne and fecal contamination. We found that birds collect plant stem material and mud for nest construction and inadvertently transport the seeds contained within. Experimental nest boxes indicated that bird nests were not passive recipients of seeds (e.g., carried on wind), but arrived in the materials used to construct nests. We germinated 144 plant species from the nests of 23 bird species. A large proportion of the nest germinants were graminoids containing self-fertilized seeds inside stems—suggesting that nest dispersal may be an adaptive benefit of closed mating systems. Avian nest building appears as a dispersal pathway for hundreds of plant species, including many non-native species, at distances of at least 100–200 m. We propose a new plant dispersal guild to describe this phenomenon, caliochory (calio = Greek for nest).

Improving runoff behavior resulting from direct inoculation of soil micro-organisms

Surface hydrology can significantly influence biological soil crusts through altering runoff behavior. Hence, micro-organisms enrichment of degraded soil crust may be a novel and practical strategy to improve soil quality and surface runoff behavior. This study evaluated the impact of inoculating (i) bacteria, (ii) cyanobacteria and (iii) bacteria+cyanobacteria on soils, with the hypothesis this would improve runoff properties. Accordingly, we assessed the influence of microbial enrichment after inoculating the native cyanobacteria (Nostoc, Oscillatoria and Lyngbya) and bacteria (Azotobacter and Bacillus) on runoff onto a degraded soil under laboratory conditions. The cyanobacteria and bacteria were isolated from the studied soil, purified and proliferated in the laboratory, and then inoculated in individual or combined treatments onto soils placed into small experimental boxes. After 15, 30 or 60 days, the treatments were subjected to a simulated rainfall. We observed a significant (p<0.01) decrease in both coefficient and peak of runoff in the bacteria, cyanobacteria, and bacteria+cyanobacteria inoculated boxes relative to the control boxes. There was also a significant (p<0.01) delay in runoff start time (38–205%) and time to peak runoff (48–52%), and decrease in coefficient (74–96%) and peak of runoff (48–86%) in the bacteria, cyanobacteria, and bacteria+cyanobacterial-treated boxes compared to the control boxes. The most effective treatment was the inoculation of cyanobacteria after 60 days (p<0.01). In this treatment, the runoff coefficient was reduced 96%, the peak reduced 83%, the start time delayed 168% and time to peak reduced by 34% compared to the control. While these results need verification in the field, they suggest that inoculation of native micro-organisms particularly cyanobacteria, can be practically used to restore local hydrological cycles in the soil.

DISCRIMINAÇÕES CONDICIONAIS ENTRE ESTÍMULOS VISUAIS E TESTES DE SIMETRIA EM MELIPONAS

Oito melíponas (Melipona quadrifasciata) foram expostas a uma versão adaptada do procedimento de emparelhamento arbitrário com o modelo (matching-to-sample) em que a presença ou ausência de luz era empregada como estímulo condicional e as cores azul e amarelo como estímulos discriminativos. As cores eram apresentadas por semicírculos de material emborrachado sustentados por duas caixas retangulares de madeira, cada uma posicionada sobre uma caixa experimental a uma distância de 15 cm uma da outra. Cada lâmpada estava localizada sobreumadascaixas. As caixas experimentais eram de material acrílico com um painel superior de alumínio. Cada caixa era equipada com um alimentador operado externamente por uma haste e possuía um conjunto de pequenos orifícios no painel de alumínio que davam acesso ao xarope. Uma abelha podia voar da colméia para o aparato experimental e obter o xarope condicionalmente ao pouso direto sobre o estímulo de comparação definido como S+ em uma tentativa particular. Depois de instalada a linha de base, foram conduzidas sondas de simetria em extinção, intercaladas com tentativas de linha de base. Nas sondas, os discos coloridos tinham a função de estímulos condicionais (as duas caixas mostravam os discos de uma mesma cor, azul ou amarelo) e a presença e a ausência de luz eram usadas como estímulos discriminativos. As discriminações condicionais foram estabelecidas com todas as abelhas e seis entre as oito abelhas alcançaram o critério de simetria emergente (ao menos cinco tentativas entre seis). Estesresultadosestendemachadospréviossobrediscriminaçõescondicionaiseemparelhamento de identidade em abelhas. Contudo, no presente procedimento os estímulos tinham posição fixa, o que permite questionar se os comportamentos observados revelam propriedades simétricas (emergentes) ou apenas o controle por componentes de estímulos compostos (diretamente aprendidos). Palavras-chave: discriminação condicional, simetria, abelhas (Melipona quadrifasciata).

An experimental test on time constraint and sexual conflict over parental care.

Because parental care is costly, a sexual conflict between parents over parental investment is expected to arise. Parental care behavior is an adaptive decision, involving trade-offs between remating, and consequently desertion of the brood, and continuing parental effort. If the main advantage of desertion is remating, then this will be a time constraint, because the deserting individual will require a certain minimum period of time to breed again in the same breeding season. So, a short breeding season should force certain individuals to desert the first brood to have enough time to successfully complete their second breeding attempt. The rock sparrow, Petronia petronia, is an unusual species in which brood desertion can occur in both sexes and the breeding season is quite short so it is a good species to investigate the role of time constraint on brood desertion. For 3 years, I investigated the brood desertion modality of the rock sparrow. Then, for 2 years, I removed a group of experimental nest boxes during the autumn. Later, I re-installed the experimental nest boxes after the start of the breeding season (2 weeks after the first egg was laid), mimicking a shortening of the breeding season for the (experimental) pairs that used experimental nest boxes. I found that in the experimental pairs, the percentage of deserting individuals was significantly higher than in the control groups, and the deserting individuals were older females. This experiment adds to our knowledge of timing of reproduction effects on individual decisions to desert by showing that a short and delayed breeding season may have different effects on males and females. To my knowledge, this is the first experimental study that demonstrates a direct link between time constraint and brood desertion.

Effects of biological rhythm disturbance on sedation induced by propofol in rats

Objective To evaluate the effects of biological rhythm disturbance on sedation induced by propofol in rats. Methods Thirty-two adult male Sprague-Dawley rats, weighing 180-220 g, were randomly divided into 4 groups(n=8 each)using a random number table: circadian rhythm+ administration during night-time group(group CN), circadian rhythm+ administration during day-time group(group CD), biological rhythm+ administration during night-time group(group BN), and biological rhythm+ administration during day-time group(group BD). In CN and CD groups, the rats were fed for 2 weeks in the experimental boxes in a 12(7: 00–19: 00): 12 h(19: 00–7: 00)light: dark cycle.While the rats were fed for 2 weeks in the experimental boxes in a 24 h light cycle.Propofol 75 mg/kg was intraperitoneally injected at 14: 00 in CN and BN groups, or at 22: 00 in CD and BD groups.The duration of loss of righting reflex was recorded.At 20 min after recovery of righting reflex, the cognitive function was assessed.The latency of passive avoidance was measured at 6, 12, 24 and 48 h after training. Results Compared with group CN, the duration of loss of righting reflex was significantly shortened, and the latency of passive avoidance was prolonged at 12 and 24 h after training in group CD, and the duration of loss of righting reflex and latency of passive avoidance at 12 and 24 h after training were shortened in group BN.Compared with group CD, no significant change was found in the duration of loss of righting reflex, and the latency of passive avoidance was significantly shortened at 24 h after training in group BD.There was no significant change between BN group and BD group in the duration of loss of righting reflex and latency of passive avoidance. Conclusion Biological rhythm disturbance can counteract circadian rhythm-produced effects on sedation induced by propofol in rats. Key words: Biorhythms; Propofol; Conscious sedation

Simulated erosion using soils from vegetated slopes in the Jiufeng Mountains, China

The effects of rainfall intensity, slope gradient and vegetation cover on the intensity of runoff and rate of soil erosion were examined with simulated rainfall. All five affected soil erosion in experimental soil boxes containing Vitex negundo var. heterophylla (VN), VN with litter (VN-L), Broussonetia papyrifera (BP), BP with litter (BP-L), and a control with bare land (BL). The presence of the vegetation and litter layers significantly reduced the rates of sediment yields, the mean rate of sediment yield values of BP-L, BP, VN-L, VN and BL were 2.873g/min, 11.264g/min, 4.220g/min, 16.781g/min and 21.594g/min, respectively. The mean rates of sediment yield increased linearly with increases of rainfall intensity and slope gradient, but not beyond a certain gradient. B. papyrifera reduced sediments by 6.24 and 25.55% more than V. negundo var. heterophylla with and without litter layers, respectively. The rate of sediment yield was positively and linearly correlated with runoff shear force, with rates increasing quickly in VN, and the critical runoff shear force of BP was 0.8282N/m2, and VN was 0.2098N/m2. The results of this study will help to determine appropriate methods for reducing soil erosion.

Spectrum of the excitedN*andΔ*baryons in a relativistic chiral quark model

The spectrum of the SU(2) flavor baryons is studied in the frame of a relativistic chiral quark potential model based on the one-pion and one-gluon exchange mechanisms. It is argued that the ${N}^{*}$ and ${\mathrm{\ensuremath{\Delta}}}^{*}$ resonances strongly coupled to the $\ensuremath{\pi}N$ channel are identified with the orbital configurations $(1{S}_{1/2}{)}^{2}(nlj)$ with a single valence quark in the excited state ($nlj$). With the obtained selection rules based on the ``chiral constraint,'' we show that it is possible to construct a schematic periodic table of baryon resonances, consistent with the experimental data and yielding no ``missing resonances.'' A new original method for the treatment of the center of mass problem is suggested which is based on the separation of the three-quark Dirac Hamiltonian into the parts, corresponding to the Jacobi coordinates. The numerical estimations for the energy positions of the nucleon and delta baryons (up to and including F-wave ${N}^{*}$ and ${\mathrm{\ensuremath{\Delta}}}^{*}$ resonances), obtained within the field-theoretical framework by using time ordered perturbation theory, yield an overall good description of the experimental data at the level of the relativized constituent quark model of S. Capstick and W. Roberts without any fitting parameters. The only free parameter of the linear confinement potential was fitted previously by Th. Gutsche to reproduce the axial charge of the nucleon. The ground state $\mathrm{\ensuremath{\Delta}}(1232)$ is well reproduced. However, nucleon ground state and most of the radially excited baryon resonances (including Roper) are overestimated. On the contrary, the first band of the orbitally excited baryon resonances with a negative parity are underestimated. At the same time, the second band of the orbitally excited ${\mathrm{\ensuremath{\Delta}}}^{*}$ states with the negative parity are mostly overestimated, while the ${N}^{*}$ states are close to the experimental boxes. The theoretical estimations of the energy levels for the positive parity baryon resonances with $\mathrm{J}=5/2$, $7/2$ are close to the experimental data. At higher energies, where the experimental data are poor, we can extend our model schematically and predict an existence of seven ${N}^{*}$ and four ${\mathrm{\ensuremath{\Delta}}}^{*}$ new states with larger spin values.

Colonization of soft sediments by benthic communities: An experimental approach in Admiralty Bay, King George Island

In order to understand nearshore biological community colonization following impact events that affect the distribution and occurrence of species and subsequent recovery a manipulative experiment was set up in King George Island. This work aimed to study colonization patterns of benthic macrofauna in defaunated soft sediment, comparing them with occurrence patterns of macrofaunal benthic organisms found in the natural soft sediment of adjacent areas, in shallow waters of Admiralty Bay, King George Island, Antarctic Peninsula. For this, a manipulative field experiment was installed through SCUBA diving at 22m depth in front of the Antarctic Brazilian Station. Samples of defaunated and natural soft-sediments were analyzed. Defaunated soft sediment in plastic boxes (a=0.02m2) were deployed in the seabed and examined after 6, 12 or 18months. Natural soft-sediment collected with cylindrical corers of 10cm in diameter (a=0.08m2), in adjacent areas at the experiment installation and during the changing and removal of the experimental boxes, were also analyzed. Altogether, 20,680 organisms belonging to 6 phyla among 42 species were identified. Thirty three taxa out of the 42 recorded were common in both natural and defaunated sediment types, 6 taxa occurred only in natural sediment and 3 taxa only in defaunated sediment. The most abundant groups throughout the experiment were: Oligochaeta, Polychaeta, Bivalvia, Gastropoda and Crustacea. In the natural sediment a total of 10 species were considered Constant, 8 species Accessory, 21 species Accidental. In the defaunated sediment 14 species were Constant, 4 species Accessory, 18 species Accidental. Analysis of variance indicated significant differences in total abundance and in Torodrilus sp. abundance in the periods of 6 and 18months, and MDS analysis showed a clear separation between natural and defaunated treatments. Torodilus sp. was the taxon with the highest relative contribution (26%) in natural sediment. In the defaunated sediment treatments, the most common taxa were cumacean Leuconidae morphotype 1 (19%) and the bivalve Yoldia eightsi (Couthouy, 1839) (18%). The statistical results indicated significant differences between the natural and defaunated treatments with respect to benthic macrofaunal associations. Species richness and abundance in defaunated treatment were less than in natural treatment. The results suggest that recovery levels in Antarctic waters after events of defaunation are very low and in order to be of value experiments may need to be for longer periods.

Patchy Distributions of Competitors Affect the Growth of a Clonal Plant When the Competitor Density Is High

Environments are patchy in not only abiotic factors but also biotic ones. Many studies have examined effects of spatial heterogeneity in abiotic factors such as light, water and nutrients on the growth of clonal plants, but few have tested those in biotic factors. We conducted a greenhouse experiment to examine how patchy distributions of competitors affect the growth of a rhizomatous wetland plant Bolboschoenus planiculmis and whether such effects depend on the density of the competitors. We grew one ramet of B. planiculmis in the center of each of the experimental boxes without competitors (Schoenoplectus triqueter), with a homogeneous distribution of the competitors of low or high density, and with a patchy distribution of the competitors of low or high density. The presence of competitors markedly decreased the growth (biomass, number of ramets, number of tubers and rhizome length) of the B. planiculmis clones. When the density of the competitors was low, the growth of B. planiculmis did not differ significantly between the competitor patches and competitor-free patches. However, when the density of the competitors was high, the growth of B. planiculmis was significantly higher in the competitor-free patches than in the competitor patches. Therefore, B. planiculmis can respond to patchy distributions of competitors by placing more ramets in competition-free patches when the density of competitors is high, but cannot do so when the density of competitors is low.

2P2-K10 力センサを用いた子どものよじ登り行動センシングシステムの開発(デジタルヒューマン)

In this study, a computational model of child climbing behavior has been developed to prevent childhood injuries by changing environmental factors. This model is constructed by probabilistically modeling the relationships among product design parameters, child characteristics, and climbing behaviors based on observed behavioral data. Large scale behavioral data are needed to apply the behavior model to every day life environment. In this paper, a system for sensing child climbing behavior is developed using strain gauge force sensors installed under experimental boxes. This system simultaneously collects force sensor data and camera data during an experiment and enables to measure child climbing behaviors toward the boxes.

EVALUATION OF SHELF LIFE AND RIPENING OF IMPORTED AVOCADO 'HASS' FRUIT FOLLOWING TREATMENT WITH E+® ETHYLENE REMOVER OR 1-METHYLCYCLOPROPENE (1-MCP) DURING MEDIUM-TERM COLD STORAGE

ISHS VI International Postharvest Symposium EVALUATION OF SHELF LIFE AND RIPENING OF IMPORTED AVOCADO 'HASS' FRUIT FOLLOWING TREATMENT WITH E+® ETHYLENE REMOVER OR 1-METHYLCYCLOPROPENE (1-MCP) DURING MEDIUM-TERM COLD STORAGE

Comparative performance of invasive alien Eichhornia crassipes and native Ludwigia stolonifera under non-limiting nutrient conditions in Lake Naivasha, Kenya

The ability of Ludwigia stolonifera to thrive in the presence of Eichhornia crassipes was investigated in Lake Naivasha, Kenya. L. stolonifera (indigenous) and E. crassipes (invasive alien) were grown in outdoor experimental boxes in monocultures and mixtures under non-limiting nutrient conditions. An additive series design with eight combinations of planting densities and four replicates was used. Competitive interactions between the two species were determined by assessing the final total biomass and above–below-ground biomass allocation after 98 days of growth. Biomass accumulation and allocation were significantly affected by competition in relation to species, with L. stolonifera accumulating more biomass than E. crassipes. ANOVA analysis indicated that there was no significant difference in Relative Growth Rate (RGR) and root/shoot ratio between monocultures and mixtures with E. crassipes. However, significant differences in RGRs were observed between monocultures and mixtures of L. stolonifera. Multiple regressions on species RGRs revealed that increasing initial biomass of a con-specific neighbour resulted to a greater reduction in species RGR in relation to increasing initial biomass of a hetero-specific neighbour. Thus, a stronger intra- than inter-specific competition coupled with the significantly higher RGR of L. stolonifera relative to that of E. crassipes enabled L. stolonifera to outperform E. crassipes.

Similar is not the same: Social calls of conspecifics are more effective in attracting wild bats to day roosts than those of other bat species

Many bat species regularly need to find new day roosts as they require numerous shelters each breeding season. It has been shown that bats exchange information about roosts among colony members, and use echolocation and social calls of conspecifics in order to find roosts. However, it is unclear if wild bats discriminate between social calls of conspecifics and other bat species while searching for roosts. Furthermore, the extent that bats are attracted to potential roosts by each of these two call types is unknown. We present a field experiment showing that social calls of conspecifics and other bat species both attract bats to roosts. During two summers, we played back social calls of Bechstein’s bats (Myotis bechsteinii) and Natterer’s bats (Myotis nattereri) from different bat boxes that can serve as roosts for these species. All experimental bat boxes were monitored with infrared video to identify the approaching bat species. Three species (M. bechsteinii, M. nattereri, and Plecotus auritus) approached the boxes significantly more often during nights when bat calls were played compared to nights without playbacks. Bechstein’s bats and Natterer’s bats were both more attracted to social calls of conspecifics than of the other species, whereas P. auritus did not discriminate between calls of either Myotis species. Only Bechstein’s bats entered experimental boxes and only at times when calls from conspecifics were played. Our findings show that wild bats discriminate between social calls of conspecifics and other bat species although they respond to both call types when searching for new roosts.

Crescimento e deposição de nutrientes nos órgãos de frangos de corte de duas linhagens comerciais

O objetivo neste trabalho foi estudar o perfil de crescimento e a deposição de nutrientes nos órgãos (coração, fígado, moela, intestino e proventrículo) de frangos de corte das linhagens Ross e Cobb de ambos os sexos. Foram utilizados 1.920 pintos de 1 dia alojados em boxes de galpão experimental em piso. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 2 × 2, composto de dois sexos (machos e fêmeas) e duas linhagens (Ross e Cobb), com quatro repetições de 120 aves. As aves foram alimentadas com rações formuladas de acordo com suas exigências nutricionais em cada fase de criação. Os pesos dos órgãos e de seus componentes (água, cinzas, proteína e gordura) foram obtidos semanalmente, com os parâmetros estimados pela equação de Gompertz e as taxas de crescimento determinadas por meio das derivadas das equações. Não houve influência da linhagem nas taxas de crescimento e deposição de nutrientes no coração. As aves Ross foram mais precoces no crescimento e na deposição de água e cinzas no fígado, portanto apresenta maior atividade metabólica na digestão e síntese de nutrientes. A linhagem Cobb foi mais precoce no desenvolvimento do intestino e crescimento e na deposição de nutrientes no proventrículo. Os machos são mais precoces que as fêmeas na taxa de crescimento e deposição de proteína, gordura e água na moela.

Cimex pipistrelli (Heteroptera, Cimicidae) and the dispersal propensity of bats: an experimental study

Previous results have shown frequent movements of crevice-dwelling bats between different shelters. Low roost fidelity of some dwelling bat species reduces the reproductive success of ectoparasites. The question of whether high densities of bat bugs (Cimex pipistrelli) represent a cost for crevice-dwelling bats (Pipistrellus pygmaeus), resulting in roost switching, has been examined. Sessions in a volary equipped with two bat boxes were carried out. One of the boxes was loaded with ectoparasites (low and high densities), the other served as a control and new roost for bats, which left the loaded box. Differences in the level of bat self-grooming, movements inside experimental boxes, and leaving the boxes between experiments with bat bugs and controls were significant. Allogrooming was observed only in few cases; therefore, the hypothesis of cooperation among individual bats in defense against bat bugs was rejected. Experiments with artificial parasitation, when bugs were added to a bat roost, showed that leaving a confined roost infested by bat bugs, i.e., roost switching, is a natural reaction of crevice-dwelling bat species, which reduces parasite load.

Preferred Feeding Sites and Prey of the Adult Gold-spotted Pond Frog, Rana plancyi chosenica

To determine the feeding sites preferred by adult gold-spotted pond frogs, Rana plancyi chosenica, and the foods that induce favorable growth of the frogs in the laboratory, we conducted two separate experiments between 27 May and 12 July 2007 in a vivarium. In the first experiment, we counted the number of crickets eaten by four gold-spotted pond frogs in a 60 min period at four different feeding sites within the experimental arenas: on the water surface, at the edge of a pond, and at two terrestrial sites. Adult gold-spotted pond frogs ate more crickets on the water surface and at the edge of the pond than the terrestrial sites. In the second experiment, we measured the growth of SVL (snout-vent length) and body mass of adult gold-spotted pond frogs fed crickets, mealworms, maggots, or earthworms in individual experimental boxes over a one month period. The SVL and body mass of the adult gold-spotted pond frogs fed crickets, mealworms, or maggots were greater than those of the frogs that were fed earthworms. These results indicate that providing crickets, mealworms, or maggots on the water or at the edge of a pond should induce favorable growth of captive-reared adult gold-spotted pond frogs.

An Experimental Test of Snake Skin Use to Deter Nest Predation

Abstract Abstract Some bird species utilize snake skins as nesting material, possibly to decrease predation. We constructed 60 artificial nests simulating the nests of Great Crested Flycatchers (Myiarchus crinitus) in nest boxes to test the prediction that snake skins deter nest predators. Twenty of the boxes lacked rat snake (Elaphe obsoleta) skins (control), 20 had a single skin in the nest, and 20 had a skin in the nest and another displayed outside the box. Five of the control boxes were depredated (20%), while none of the experimental boxes were depredated. Our results supported our prediction that use of snake skins would deter mammalian predators, particularly the southern flying squirrel (Glaucomys volans). Although our results suggest a potential adaptive explanation for this behavior, our design did not allow us to address the degree of olfactory or visual detection by the squirrels, and left other potential explanations untested.

AN EXPERIMENTAL TEST OF SNAKE SKIN USE TO DETER NEST PREDATION

Abstract ABSTRACT Some bird species utilize snake skins as nesting material, possibly to decrease predation. We constructed 60 artificial nests simulating the nests of Great Crested Flycatchers (Myiarchus crinitus) in nest boxes to test the prediction that snake skins deter nest predators. Twenty of the boxes lacked rat snake (Elaphe obsoleta) skins (control), 20 had a single skin in the nest, and 20 had a skin in the nest and another displayed outside the box. Five of the control boxes were depredated (20%), while none of the experimental boxes were depredated. Our results supported our prediction that use of snake skins would deter mammalian predators, particularly the southern flying squirrel (Glaucomys volans). Although our results suggest a potential adaptive explanation for this behavior, our design did not allow us to address the degree of olfactory or visual detection by the squirrels, and left other potential explanations untested.

Fasciola hepatica and Paramphistomum daubneyi: vertical distribution of metacercariae on plants under natural conditions.

Four experiments on the metacercariae of Fasciola hepatica and Paramphistomum daubneyi were carried out under natural conditions in order to study their vertical location on submerged plants and to determine whether simultaneous cercarial shedding of both digenea causes changes in the distributions of the metacercariae. These experiments were performed in experimental boxes, each containing six tufts of rushes. Most metacercariae (73.0%) of F. hepatica were found along the walls of boxes, while 81.5% of P. daubneyi metacercariae were found on rush stems. In the case of snails infected by either of the two digenea, 80.1% of F. hepatica cercariae encysted on submerged parts of rushes and of the box walls near the water surface (to a depth of 1 cm), whereas 73.0% of P. daubneyi metacercariae were found in the lower sections (from -4 to -7 cm). If snails dually infected with P. daubneyi and F. hepatica were used, the vertical distributions of the metacercariae were significantly different from those found for snails infected by either of the two digenea. If snails having 42-day old infections with F. hepatica and other snails with 70-day old infections with P. daubneyi were simultaneously introduced into the boxes, the frequency of F. hepatica cysts was significantly lower in the section located under the water surface (29% only), while the frequencies of metacercariae in the lower sections (from -1 to -5 cm) were increased. Some significant changes were also observed for the metacercariae of P. daubneyi. The disturbance noted in the vertical distributions of F. hepatica and P. daubneyi metacercariae suggest that the encystment of F. hepatica cercariae can be disturbed by the simultaneous encystment of P. daubneyi cercariae, or conversely.