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The study was carried out infourselected farmer’s pond in Netrokona sadarand Barhatta upazillas(sub district) under Netrokona district during April to September 2019 having average pond area of 0.14 haeach. The ponds were prepared by removing aquatic vegetation and unwanted fish and other animals, andapplying with lime at the rate of 250 kg/ha. Five days after liming, water was supplied from shallow tubewell to the ponds and filled up to the depth of 1.5 m. The fry of Pabda (Ompok pabda) and Gulsha (Mystuscavasius) with Rohu (Labeo rohita) were stocked at the rate of 175000; 87,500 and 2000/ha, respectively.After stocking, fish were fed at a rate of 5-12% of body weight with supplementary feed (30% crudeprotein). Fish sampling were done at monthly interval to know the fish growth status and also to adjust feedration. After six months rearing, fish were harvested by repeated seine netting. Total bulk weight and numberof fish from each pond was recorded. Survival and gross production of fish of each pond were estimated. Theharvesting weight of pabda ranged from 33 to 36g. While the harvesting weight of Gulsha and Rohu rangedfrom 26-27g and 591-614g, respectively. Based on the number of fish harvested at the end of the experiment,survival ranged from 75 to 88%.Total production of Pabda (O. pabda) and Gulsha (M. cavasius) with Rohuwas estimated at 5202, 1772 and 1066 kg/ha, respectively. The total production of fish as recorded in trialponds were 8043 kg/ha

Asexual species are thought to suffer more from coevolving parasites than related sexuals. Yet a variety of studies do not find the patterns predicted by theory. Here, to shine light on this conundrum, we investigate one such case of an asexual advantage in the presence of parasites. We follow the frequency dynamics of sexual and asexual Daphnia pulex in a natural pond that was initially dominated by sexuals. Coinciding with an epidemic of a microsporidian parasite infecting both sexuals and asexuals, the pond was rapidly taken over by the initially rare asexuals. With experiments comparing multiple sexual and asexual clones from across the local metapopulation, we confirm that asexuals are less susceptible and also suffer less from the parasite once infected. These results are consistent with the parasite‐driven, ecological replacement of dominant sexuals by closely related, but more resistant asexuals, ultimately leading to the extinction of the formerly superior sexual competitor. Our study is one of the clearest examples from nature, backed up by experimental verification, showing a parasite‐mediated reversal of competition dynamics. The experiments show that, across the metapopulation, asexuals have an advantage in the presence of parasites. In this metapopulation, asexuals are relatively rare, likely due to their recent invasion. While we cannot rule out other reasons for the observed patterns, the results are consistent with a temporary parasite‐mediated advantage of asexuals due to the fact that they are rare, which is an underappreciated aspect of the Red Queen Hypothesis.

Magnetotactic bacteria (MTB) synthesize ferrimagnetic crystals that contribute to the remanent magnetization in sediments, yet knowledge of how MTB populations vary in natural environments over time remains limited. We report abundances of three MTB morphotypes from nine sites collected and measured every month over a two-year period from a natural pond near Munich, Germany. Morphotype populations underwent coherent temporal trends among the nine sitesespecially at proximal sites with similar water depths. MTB populations varied independently of bottom water oxygen concentrations or temperature over the two-year period, except for spirilla, which flourished during the summer at some sites. Magnetic properties of the sediments did not reflect living MTB abundances, but instead varied with water depth. Deeper sites, which were also lower in organic carbon, nitrogen, and oxygen concentrations than shallower sites, had higher saturation magnetizations and were richer in single-domain particles.

An experiment on sound propagation in a shallow natural pond covered with an ice layer is described. The results from processing the experimental data are presented. It is found that the sound propagates along the ice-covered water layer and at the pond’s bottom. The corresponding velocities are determined.

Interspecific hybridization has been occasionally reported for various combinations of geoemydid turtles, but genetic consequences of such hybridization have rarely been investigated. We surveyed the hybrid status of 40 individuals from a seemingly hybridizing turtle assemblage in a natural pond in northcentral Honshu, Japan. Analysis of mtDNA sequences confirmed that the parental species of this assemblage were Mauremys reevesii (Chinese three-keeled pond turtle) and Mauremys mutica (Asian yellow pond turtle), neither of which is native to the main islands of Japan, although M. reevesii was naturalized in the area before the 19th century. Extensive examination of pure strain samples of the 2 species yielded 10 morphological and 10 genetic diagnostic characters (allozyme and short interspersed repetitive elements) that were used to determine the hybrid status of the turtles in the assemblage. Morphological examination showed that 19 out of 40 individuals were not different from pure M. reevesii i...

Aim The activity of chitosan microparticles (CM) was examined using a matrix of conditions in order to assess the efficacy of CM as a mitigation against various strains of Salmonella enterica in agricultural water. Methods and Results Different concentrations of CM (0, 0·01, 0·1, 0·2, 0·3% w/v) were examined for antimicrobial activity against log vs stationary phase cells of Salmonella and at different conditions of temperature, salinity and pH. Results showed greatest activity with 0·3% CM at pH 7, 25–37°C without additional of salt. Significant reductions in Salmonella levels were also achieved in natural pond water, although decreases were reduced compared to sterile water. All serotypes were sensitive to CM, with minimal inhibitory concentrations ranging from 0·0031 to 0·0250% w/v. Phylogenic analysis of Javiana strains showed increased resistance appeared in multiple genetic lineages. Conclusion Conditions demonstrating greatest CM activity were compatible with agricultural practices. Although sensitivity to CM varied among Salmonella strains, all strains were sensitive under conditions examined in this study. Significance and Impact of the Study This research indicated that CM, a natural compound with minimal environmental impact, could be an effective alternative for mitigating Salmonella in agricultural water applications.

In this paper we consider usage of duckweed for national economy: for lifestock feed, for bioethanol and biogas production, in medicine and for phytoremediation. Cultivation of duckweed Lemna minor in conditions of St.Petersburg was carried out in order to obtain biomass. Two cultivation variants were studied: in a natural reservoir and in an artificial reservoir during a period from May to July 2017. The following cultivation conditions were determined: lighting, temperature. The population growth intensity was estimated. The most favourable conditions appeared to be at natural pond in Petergof. Daylight features, lightning intensity of the Leningrad Oblast’ are less favourable than that for south Russian regions, so biomass production rate is drastically lower. The obtained L. minor biomass was dried out under the infrared lamp up to constant weight. The obtained dry biomass was used to produce lipids extracts by Sohxlet technique. Lipids output was 4% of dry biomass for duckweed grown in natural pond and 6% for duckweed grown in artificial pond. Most likely it is driven by stress factor of duckweed growth, which is limited by insufficient solar illumination. The lipid output of duckweed is not high, but we are planning to choose optimum cultivation conditions for duckweeds, which will result in increased lipids output.

Genetic variation complicates predictions of both the initial tolerance and the long-term (micro-evolutionary) response of natural Daphnia populations to chemical stressors from results of standard single-clone laboratory ecotoxicity tests. In order to investigate possible solutions to this problem, we aimed to compare the initial sub-lethal tolerance to Cd of 10 naïve natural pond populations of Daphnia magna as well as their evolutionary potential to develop increased resistance. We did so by measuring reproductive performance of 120 clones, i.e. 12 clones hatched from the recent dormant egg bank of each of 10 populations, both in absence (Cd-free control) and presence of 4.4 μg Cd/L. We show that the initial tolerance, defined as the reproductive performance of individuals of the first generation exposed to Cd relative to that in a Cd-free control was not significantly different among the 10 studied pond populations and averaged 0.82 ± 0.04 over these populations. Moreover, these populations' initial tolerances were also not significantly different from the mean initial tolerance of 0.87 ± 0.08 at 4.0 μg Cd/L measured for a group of 7 often-used laboratory clones, collected from a range of European ecotoxicity testing laboratories. This indicates that the initial response of naïve natural pond populations to sub-lethal Cd can be relatively accurately predicted from ecotoxicity test data from only a handful of laboratory clones. We then used estimates of broad-sense heritability of Cd tolerance (H(2)) - based on the same dataset - as a proxy of these populations' capacities to evolutionarily respond to Cd in terms of the development of increased resistance, which is here defined as the increase with time of the frequency of clones with a higher Cd tolerance in the population (accompanied with an increase of mean Cd-tolerance of the population above the initial tolerance). We show that the populations' estimated H(2) values of Cd-tolerance cover almost the entire theoretically possible range, ranging from not significantly different from zero (for five populations) to between 0.48 and 0.81 (for the five other populations). This indicates that, unlike the initial tolerance to Cd, the (long-term) micro-evolutionary response to Cd may be very different among natural pond populations. Therefore, we conclude that it may be very difficult to predict the long-term response of an unstudied population to chemical stress from tolerance data on a sample of other populations. It is therefore suggested that new methods for forecasting long-term responses should be explored, such as the development of predictive models based on the combination of population-genomic and tolerance time-series data. publisher: Elsevier articletitle: The initial tolerance to sub-lethal Cd exposure is the same among ten naïve pond populations of Daphnia magna, but their micro-evolutionary potential to develop resistance is very different journaltitle: Aquatic Toxicology articlelink: http://dx.doi.org/10.1016/j.aquatox.2013.10.016 content_type: article copyright: Copyright © 2013 Elsevier B.V. All rights reserved. ispartof: Aquatic Toxicology vol:144 pages:322-331 ispartof: location:Netherlands status: published

We compared production variables between channel catfish, Ictalurus punctatus, nursery ponds fed according to industry standards, that is feeding immediately at stocking, to an alternative practice of delaying feeding for 6 wk after stocking in an effort to utilize natural pond productivity and reduce feed use. Twelve 0.04 ha ponds were fertilized and stocked with swim-up fry (4–5 d posthatch) at a rate of 10,000/pond (250,000/ha). Ponds were then randomly assigned to either the standard feeding protocol (feeding daily starting immediately at stocking) or an alternative feeding protocol (no feeding until 6 wk post-stocking). After 18 wk of production, there were no differences in water quality or zooplankton abundance between the two treatments. Fish length was not affected by treatment throughout the study, and survival and total weight harvested were similar. Total kg of feed fed was significantly reduced in the delayed feed treatment, averaging 26 kg/pond less feed fed. If proper fertilization practices are implemented, large numbers of desirable zooplankton for catfish fry culture are attained, and these zooplankton are able to sustain catfish fry stocked up to 250,000/ha. Therefore, no commercial diets are required during the first 6 wk of culture, saving over $95.55/ha in initial feed costs.

Background: Untreated disposal of chemical waste poses serious environmental hazard. An attempt was made towards presumptive identification of the major genera of microbial contaminants found in a natural pond that receives waste from a pharmaceutical industry of Gonoshasthaya Antibiotic Ltd. during the period of 2008 to 2009. Methodology: Water sample was collected and physical parameters were determined. Results: A total of 38 bacterial isolates were found from surface water, deep layer water and sediment soil but only five isolates were found to resist up to 0.1 mg/ml of phenol. Microscopic and biochemical test of five isolates presumptively identified them Staphylococcus sp, Sporosarcina sp, Bacillus sp and members of family Enterobacteriaceae. All five isolates were resistant to Amoxycillin (30?g), Erythromycin (15?g), and Penicillin-G (10units). Conclusion : Resistance against common therapeutic antibiotics indicates possible epidemiological risk. Bangladesh Journal of Medical Science Vol. 12 No. 03 July ’13 Page 310-314 DOI: http://dx.doi.org/10.3329/bjms.v12i3.15431

In a natural pond among usual black larvae of the common toad (Bufo bufo L.), a few unusual individuals of red-olive coloring were found out. In both morphs we investigated the melanophores of skin using different methods. The ESR-spectrometric analysis has shown the absence of distinctions between morphs by the amount of melanin. Analysis of total preparations of skin has shown the presence of various kinds of melanophore cells both in the derma and in the epidermis. Among typical melanophores, essentially differing cells appeared (atypical cells). In black morph tadpoles, the number of all kinds of melanophores is significantly greater than in red-olive morphs. It is shown that dark coloring is connected with a considerable number of atypical cells in the epidermis imposed on a dense layer of typical dermal melanophores with dispersed melanin.

A lens based on liquid in the confined volume of a volumetric flask was presented as a potential projector to observe microscopic floating organisms or materials. In this experiment, a mosquito larva from a natural pond was selected as a demonstration sample. By shining a light beam from a laser pointer of any visible wavelength through the volumetric flask filled with liquid, the movements of floating objects were clearly observed on a screen. The magnification was simply controlled by changing either the volume of the flask or the distance of the screen from the flask.

The research treats the lakes of the Guangzhou Higher Education Mega Center(HEMC) as the main research objects. According to the relationship of the lakes and university city drainage system,lakes are the accepter of rain and sewage.In fact, the lakes of HEMC can be divided into five categories,our researches choose the natural pond,ornamental pond , the oxidation pond as the main bodies of researches，which have a great impact on environment and people. The lakes of HEMC are not a source of drinking water. We select the phosphorus, nitrogen, COD, Fe, Mn, and ctc. as the main indexs of water quality assessment. The results of the typical sampling points are under the surface water environment quality standard for level Ⅴ. The main pollutants are TN and TP. According to the situation of the lakes, putting forward views to improve the water quality.

Stocking density is considered a priority topic in aquacultureresearch due to its bearing on the welfare of farmed fish and the need forfuture recommendations governing stocking density management on fishfarms. This study was carried out to investigate the growth performanceand feed utilization response of sea bass (Dicentrarchus labrax) todifferent stocking densities. Two duplicate groups of sea bass (meanBW=32.83 g) were reared in six cages (2 m3 each) suspended at naturalpond with a proximate area of 20 hectare at three stocking densities (30,45 and 60 fish/m3 equal to 1.0, 1.5 and 2.0 kg/m3) for 225 days.Significant differences (P≤0.05) on final fish weight, weight gainand daily gain were observed. Fish reared at the highest densities (60/m3)had the lowest mean final body weight (225 g) while those of the lowestdensities (30/m3) showed the highest mean final body weight (270 g)while (45/m3) are in between. The differences between the lowest andhigher density was 20%. A similar tendency was observed for SGR, 0.85and 0.92 in the highest and lowest densities, respectively.Significant difference in FCR were observed groups ranging from2.76 to 3.24 by about 17% between the lowest and highest density.Survival rate was insignificantly (P≤0.05) affected and was around 96%independently of the density and the period. Part of the mortalityobserved was due to fish jumping out of cages and other part aftersampling. Regarding economic efficiency the net returns of cageimproved with increasing density and the best net returns was observedwith the density 45/m3 followed by densities 60 and 30 fish/m3respectively.In conclusion the best density was 45 fish/m3 which improved by33% than the lowest density (30 fish/m3, one kg/m3) and 17% than thehighest density (60 fish/m3, 2.0 kg/m3) for economical evaluation.

Seed collection and storage of wild species in ex-situ seed banks should be continued as an integrated tool for the conservation of plants in their habitats. Although seed-bank facilities are widely used today, their seed samples often suffer low genetic diversity. Consequently, reintroduced seeds and plant material may not have the resilience to cope with future environmental stress so leading to complete wastage of seeds. Molecular techniques allow the benefit of quantification of the genetic diversity of a seed collection in comparison with that of the natural population. In this study we focus on ex-situ seed bank samples and living collections of Ranunculus peltatus subsp. baudotii. We compare their genetic diversity and structure with that of the natural population before and after undertaking a restoration project on a natural pond in the Tuscan Archipelago National Park. ISSR analyses, carried out on a total of five sampling groups, shows a relatively high level of genetic diversity for the ex-situ cultivated groups. The analysis of molecular variance, in agreement with clustering obtained in the neighbour-joining dendrogram and with the pattern from cluster analysis, suggests dividing the samples analysed into two groups: one formed by individuals sampled before the pond restoration and the other formed by the subsequent pond population. The results highlight the importance of planning mixed propagation lines which can be obtained through the use of a range of germination conditions to exploit a novel source of genetic variability which may otherwise remain hidden within the seed collection.

Commercial shrimp farmers must continually assess strategies to reduce operating costs and increase production in an effort to maximize profitability. One common approach is to promote natural productivity in the culture system to provide supplemental food resources for the target species. Anderson et al. (1987) reported that 53‐77% of the growth of juvenile Pacific white shrimp, Litopenaeus vannamei, raised in earthen ponds was because of the assimilation of in situ natural pond biota. Epp et al. (2002) estimated that as much as 31% of the nitrogen requirements of L. vannamei were obtained from natural production. Bianchi et al. (1990) reported that 70‐80% of the weight gain of L. vannamei reared under laboratory conditions was attributed to the consumption of bacterial floc. Additionally, several studies conducted at the Oceanic Institute (OI, Waimanalo, HI, USA) have shown that growth rates of juvenile L. vannamei reared under intensive culture conditions were significantly enhanced when shrimp were grown in organically rich pondwater versus clear

Suction pile anchors are large cylindrical (inverted bucket type structure) open at the bottom and closed at the top and largely used for mooring of offshore platforms, exploratory vessels etc. Prediction of the mooring capacity of suction piles is a critical issue faced by the design engineers and rational methods are required to produce reliable designs. Tests have been conducted in an existing natural pond within NIOT campus with the objective of developing methodology of deployment, design and logistics for suction pile installation and testing of mooring capacity under static pullout. Small size suction piles with varying diameters and lengths have been used in the tests. The tests have been carried out in the natural pond with constant water depth of 1.5 m with the top 1.5 m layer of bed comprising soft marine clay. It is found that pile geometry, aspect ratio and angle of pullout have a significant influence on the response to pullout. As angle of mooring load application changes from vertical to horizontal the reaction offered by the suction pile changes from skin friction to passive soil resistance. Resistance offered by the internal plug of soil is found to vary according to dimension of the anchor piles.

A comparison is made between the performance of a three-pond natural sedimentation domestic wastewater treatment plant and two laboratory pilot systems with respectively one and two tanks, using the same raw effluent to validate them as models. A number of physico-chemical and biological parameters were examined. Principal component analysis (PCA) was applied to the reference plant and each of the pilot plants. Field monitoring of the reference plant by weeky sampling for 1 year showed that the first sedimentation pond was the most important in the treatment process. Only slight differences were found, for all the parameters studied except bacteria, between the outflow from the first pond and the outflows from ponds 2 and 3. On the laboratory pilot plants, an initial stabilization period of about 1 month was found necessary to simulate the natural reference plant accurately; the first tank likewise supplied most of the treatment effect. Yields were generally better in the pilot systems operating at 20°C with constant flow rates and controlled light than in the reference plant. Overall, the results obtained show that a natural wastewater sedimentation plant can be accurately simulated by pilot systems, and in particular by a one-tank system. In the future, these model systems should enable us to study the influence, transfer and/or elimination of various micropollutants in this type of ecosystem.

Most abandoned ponds can be upgraded as detention or retention ponds. However, some of the abandoned mining ponds have been used in an improper way such as for illegal landfill sites. The selected ponds in this study fulfil the characteristics as retention ponds in terms of location, pond capacity, inlet and outlet discharges and the facilities installation. Design rainfall was obtained from MASMA manual using Bagan Serai design storm coefficient. The peak flow rate for the drainage system was designed in 10 years ARI due to having the development of housing and industrial areas. The results show that the peak runoff by using design rainfall is much higher than the peak flow from current rainfall. The volume of the pond has been designed for 10, 50 and 100 years ARI (Average Recurrence Interval). The storage can be exceeded up to 130000m whereas the availability of this natural pond is up to 156000m. Thus it is concluded that the capacity of the ex-mining pond is sufficient to cater for the runoff from catchment areas. The abandoned mining pond has the potential to be developed as part of the infrastructure in future.

As we said, the exemplar is the natural object or process which is chosen as the target of the reproduction. More precisely, we should say that a naturoid is the reproduction of the representation of the exemplar, which the artificialist generated in his own mind. Models, even purely mental ones—in the technological design as well as in art—are examples of formalized representations which function as pilot maps or schemes of the natural object or process which we wish to reproduce.

We document morphological variation and its association with larval cannibalism in a population of long-toed salamanders, Ambystoma macrodactylum columbianum. Larvae observed in a natural pond engaged in cannibalism. Additionally, these larvae possessed significantly longer and wider heads, as well as larger vomerine teeth, than did conspecifics of the same size reared in the laboratory for 1 month after capture. This variation in trophic structures is consistent with the characteristics of "cannibal" morphs that have been documented for larvae of another salamander species. We extend current knowledge of the development of this morphology by using multivariate statistical analysis to examine, further, a possible basis for this variation in head shape. Principal component analysis indicated that after the removal of the effects of body size, variation in the distance between the eyes (interocular width) accounted for most of the remaining total overall variation in head shape. Multivariate ontogenetic trajectories of head shape, constructed from linear regressions of principal components (measures of size and shape), were equivalent for the two larval samples. These statistical analyses indicate that this trophic polymorphism is not due to differences in either the rate of change in head shape relative to overall size or the size at which the divergence in head shape begins. Rather, morphological variation in larval A. m. columbianum may be due to fluctuations in the presence of key, influential environmental factors, as has been demonstrated for other larval amphibians that exhibit trophic polymorphism.

The structural and functional properties of an experimental field station for the evaluation of the ecotoxic potential of xenobiotics in static freshwaters are introduced. Eight mesocosms of one cubic metre seize were installed in a natural pond representing a set of small, almost identical test biotopes. By regular measurements of the biotic and abiotic parameters the usefullness of this systems to determine toxic threshold limits under realistic conditions was documented.

Optimal harvest management to obtain maximum yield of waterhyacinth is studied theoretically and experimentally. Theoretical analysis, based on logistic curve for a growth of waterhyacinth, shows that maximum yield is obtained by constantly harvesting only growth parts of it and keeping the population density of Sm/2 (Sm : saturation value of logistic eq.).However, it also shows that its yield hardly depends on a harvest period of waterhyacinth up to 30 days if the value of Sm/2 is between upper and lower density of population in the period. These conclusions were supported by two experiments : Experiment I for 9 months and Experiment II for 15 months in a natural pond. Mean yield and nitrogen removal in the later experiment with the harvest management, which followed almost the above mentioned technique, were up to about 90% of theoretical maximum yield (Smλ /4) and maximum nitrogen removal (Smλ N/4) (λ : growth coefficient in logistic eq., N : total nitrogen content in tissues of waterhyacinth).

It is generally assumed that shrimp cultured in intensive aquaculture systems receive little or no nutrition from natural pond biota. However, recent experiments indicate that even under intensive growout conditions, shrimp growth is enhanced by unknown growth factors produced autochthonously in an intensive shrimp pond. As part of an ongoing research effort to characterize the growth factors contained in shrimp pond water, an experiment was conducted to compare the effects of pond water, with selected solid fractions removed, on the growth of juvenile white shrimp, Penaeus vannamei. Fractions were removed from pond water by passing the water through a series of mechanical and activated carbon filters. In the presence of water-column solids between 0.5 and 5.0 μm, shrimp growth rates increased by 53% over growth rates attained in clear well water, while solids > 5.0 μm improved shrimp growth by an additional 36%. These solids consisted predominantly of microalgae and microbial-detrital aggregates. Solids

1 The population dynamics of a natural population of Sympetrum danae (Sulzer) were studied, by means of a mark—release—recapture method, to find indications of dispersal by mature adults. Additional information on orientation and the influence of phenotype (including age), density and weather was obtained by observations under natural conditions and in a large outdoor field cage. 2 80% of all mature adults caught around the natural pond were estimated to be immigrants. Considerable immigration was confirmed by the abdomen length of unmarked matures which did not accord with that expected from the locally emerged population. Total numbers captured and the minimum number known to be alive fell sharply at the time when most individuals were mature. At the same time, new matures continued to enter and disappear from the study area at an increasing rate. 3 Dispersive behaviour (escape flights) in the field enclosure was primarily age dependent in both sexes: it occurred from an age of 25–30 days onwards. This coincides with the time-lag between the emergence peak and increased dispersal in the field. Secondary effects on escape flights suggested that males tended to abandon low density areas. 4 Males flew relatively more southward than females.

Long‐term experiments were carried out under natural pond conditions to study the effects of 3,4‐dichloroaniline (DCA) on plankton communities. DCA was kept at concentrations of 50±30 μg/l for 55 days and at 25±15 μg/l for additional 25 days; it had to be applied several times because of its loss (rate 0.06–0.14 d‐1). The most sensitive species was Daphnia longispina; the number of individuals was significantly lower as a consequence of DCA; therefore the threshold concentration for outdoor populations is below 25 μg/l.

A research study was conducted to investigate the culture possibility of fresh water catfish Pangasius pangasius with formulated feed in natural ponds. The stocking density was chosen as 8000 fry/ha with an initial weight of 42.57±2.51 g. The formulated feed contained 45% fishmeal, 30% mustard oil cake, 15% wheat bran and 10% rice bran to supply 40.48% protein in feed. The growth of Pangasius pangasius in terms of net weight gain was found as 266.49g, which was statistically significant (p

This chapter describes a 16-year study, in which it has been found that pond hydroperiod is a primary source of variation in community structure for a natural community of pond-breeding amphibians. Larval competition and predation form other axes that are positioned along a continuum of hydroperiod, and the strength of their influence on the success of species is mediated by pond hydroperiod. Although hydroperiod, competition, and predation had a detectable influence on the amphibian community at Rainbow Bay, the effects of these factors were often difficult to separate. Correlative analyses are less powerful for sorting out confounding factors than manipulative experiments in replicated artificial ponds. The predictor variables used are often themselves correlated. Nevertheless, in many cases, a good year for a species is also a good year for its competitors and predators. Juvenile recruitment of all species is limited by a short hydroperiod in the driest years. In years with longer hydroperiods, the density of competitors affected the number of metamorphosing juveniles per breeding females for some species. The density of salamander larvae is also a significant predictor of per-capita juvenile recruitment for anurans. A significant negative relationship is detected for two of four anuran species analyzed, most likely due to predation by the salamander larvae on the anuran tadpoles. These results indicate that community structure, at least in terms of relative abundances, varied continuously. However, regulation of community structure within a pond occurs through the predictable interaction of rainfall, hydroperiod, competition, and predation.

The waste from the production of olive oil represents a grave danger for aquatic biotopes where it is disposed of, due to its great potential for oxygen consumption. The most simple method to eliminate this waste, consists of its concentration by evaporation in natural ponds, using the sludges as agriculture fertilizer. In two ponds used for this purpose during a year we have studied the transformation that organic micropollutants suffer in these ponds. The conclusions we have come to show us that organic compounds can have two ways of evolution.

The time available for male-male competition and the sex ratios of common toads were manipulated within enclosures in a natural pond. At an even sex ratio, pairs formed at random with respect to body length of pair members. Pairs were still randomly composed at spawning. By contrast, when sex ratios were experimentally male-biased (2:1), after 3 days of male-male competition large males were over-represented in spawning pairs. When the time available for competition was longer (10 days), pairs were size-assorted. The probability of taking over a female in amplexus and resisting displacement attempts when in amplexus was a function not only of male size but also of the relative sizes of the pair members. Small males in amplexus with large females were easily displaced, as were large males coupled with small females. Pairs where the male and the female were matched in size had a higher probability of staying in amplexus than those less closely matched. Males did not discriminate between females of different sizes. These findings are in line with a hypothesis that non-random spawning patterns in the common toad are generated primarily by male-male competition. Mate choice (male or female) does not have to be invoked to explain non-random spawning patterns in this species.

SYNOPSIS. Species of sessile Stentor, Vorticella and colonial peritrichs were collected in boxtype plastic petri dishes. Thru a hole in the wall of the dish, various concentrations of mercuric chloride, a standard bactericidal agent, were introduced. Following a 3-hour exposure to the toxicant, the death of the sessile ciliates followed a set pattern with a clearcut toxicity threshold of 0.1–0.5 parts per million with an LD 50 of about 0.25 ppm. Furthermore, the sessile ciliates were not dislodged when the natural pond water in the dish was poured out and replaced with water from other sources. Various responses were elicited by 4-hour exposure to 4 changes of environment. By this procedure, the protozoan community was subjected to new sets of conditions. Such a technic could serve as a method of detecting and assessing water pollution.

Hydrophytes growing in natural ponds on the Coteau du Missouri in North Dakota have been studied. Previous studies in the same region showed how transpiration by hydrophytes could be separated from the total water loss from a natural pond, during the period that vegetation was growing in height, on the basis of a correlation between the height of vegetation and a mass-transfer coefficient. It is shown that a similar separation can be made during the period of declining activity of the vegetation. A significant correlation was found between the ratio of moisture content of vegetation to its oven-dry weight and the mass-transfer coefficient. Weekly photographs on Ektachrome Infrared Aero film helped to confirm some of the phenomena observed.

Previous laboratory studies have shown that Rana cascadae larvae preferentially associated with siblings over non-siblings in choice tests. This study, conducted during three consecutive summers, tests the hypothesis that R. cascadae larvae aggregate nonrandomly with respect to sibship in natural ponds. Pairs of sibships were reared in separate tanks or together in the same tank in the laboratory. Each sibship within a pair was then stained with neutral red or methylene blue dye and released together in a natural pond. Over a period of several days, aggregations of tadpoles within test ponds were repeatedly captured, censused for sibship composition, and released. In control tests, two groups of tadpoles from the same sibship were dyed different colors and released together. In total, 25 different tests were conducted using tadpoles from 31 sibships and 456 aggregations were sampled. The distribution of color compositions of aggregations in control tests did not differ from an expected random distribution. Color compositions of aggregations in experimental tests differed from controls and from an expected random distribution. Aggregations in these tests tended to be dominated by one of the two colors (sibships). We conclude that R. cascadae tadpoles recognize and prefer to aggregate with siblings in natural field conditions. Circumstances of early rearing (i.e., whether tadpoles were reared with siblings or in mixed sibling/non-sibling groups) had no influence on preferences to associate with siblings, but there was an inverse correlation between group size and sibling association.

The use of diethyl 3,5,6-trichloro- 2-pyridyl phosphorothionate (Dursban) as a larvicide has increased in the past few years. It is a moderately persistent organophosphorus pesticide and has an adverse effect on fresh water phytoplankton. The recommended application rate of Dursban is 0.0125 lb/acre. ROBERTS and MILLER (1970) found that Dursban as the concentration of 0.4 ppm prevented the growth of fresh water Diatoms. HURLBERT et al. (1972), using shallow artificial ponds, found that Dursban applied at the rate of 0.025 lb/acre stimulated the growth of blue green algse. The results of the present paper describe the effect of small amounts of Dursban upon fresh water phytoplankton present in a large natural pond situated adjacent to the Canadian shore of Lake Huron. The experiments were carried out during the months of July and August in 1973 and 1974. METHODS AND MATERIALS

Le 19 juillet 1928 l'auteur trouva près de Natal, capitale de l'État de Rio Grande do Norte, a 5º 47' au sud de l'équateur, un nouveau Dendrocephalus qui portera le nom ornatus, dû a ses appendices caudales teints d'écarlate brillant. La femelle (Pl.1) atteint 12 mm. de longueur e contient des oeufs noirs dans sa cavité d'incubation. Le mâle, beaucoup plus robuste, atteint 16 mm. et montre, outre les caracteres sexuels, une modification extrémement compliquée des deuxièmes antennes (qui dans la planche II sont vues devant les premières). L'espèce est plus petite que les deux autres décrites de l'Amérique du Sud et se distingue facilement par les antennes du mâle. Elle fut trouvée au bord de la route dans une flaque large et profonde d'eau de pluie argileuse. Les exemplares rapportés moururent en quelques jours et la mare, lors d'une seconde visite, fut trouvé sèche. L'autre espèce, observée en 9. 7. 28 dans un étang naturel tout-près de la capitale, avait déjà été observée á Matto Grosso et en Paraguay et déterminée comme Cyclestheria hislopi BAIRD. THIELE pense que les individus de l'Amérique du Sud, pour cause de quelques petites différences, pour-raient nien former une autre espèce qu'il propose d'appeler sarsiana, mais la comparaison des desseins et descriptions avec mes exemplaires ne parait pas soutenir cette idée. Tout-de-mème la répartition connue de cette espèce est extrêmement curieuse et peut-être unique en zoologie. Elle a été signalée à Nagpur (Hindoustan), Ceylon, Queensland (Australie), Célèbes, Afrique orientale et Sansibar; seulement le premier lieu se trouve bien au nord de l'équateur, mais encore dans la zone tropicale, comme toutes les autres localités. L'explication de cette extension sur les deux mondes est tout ce qu'il a de plus difficile, puisque entre les localisations il n'y a pas seulement d'énormes distances sur terre (que l'on pourrait expliquer par un défaut d'observations), mais des espaces tres étendus, occupés par la mer. L'intervention de l'homme ne saurait expliquer ces faits et le transport par les oiseaux aquatiques ne pourrait être qu'un fait tout-a-fait excepcionnel pour les grands trajets océaniques. Le recours aux terres hypothétiques, qui formaient des ponts intercontinentaux dans des périodes géologiques extrêmement reculées, recontre des objections évidentes. En tous les cas on ne peut qu'admirer la constance avec laquelle le type de l'espèce s'est maintenu durant d'innombrales générations et a travers de telles distances quand les autres phyllopodes ont formé non seulement des variétés, mais même un grand nombre de genre et de familles. On the 10th of july the author found about 36 km. from Natal, capital of the brazilian State Rio Grande do Norte, at 5º 47' southern latitude, a new kind of Dendrocephalus which he proposes to name ornatus on account of the brillant scarlet colour of the caudal appendices. The female (Pl. 1) reaches 12 mm. in length and shows black eggs in its breeding cavity; the male attains 16 mm. and is much stouter, while its second antennae (which in Pl. 2 are seen in front of the first pair) show the most complicated structure, so far seen and delineated. They form the principal feature of the species which was caught in the muddy water of a large and deep puddle, formed by rain at the side of the road. This later dried up, while the specimens brought alive to the capital died in a few days. The second species, a Cyclestheria, was observed in a permanent natural pond in a suburb of Natal. Like other specimens from Matto Grosso and Paraguay, it was determined as hislopi BAIRD, the only known species. THIELE thought that the brazilian species might be separated under the name sarsiana, but the comparison of the specimens with other descriptions and drawings does not support this view. The strangest fact about this species is its distribution which includes western India (Nagpur), Ceylon, Australia (Queensland), Celebes, East Afrika and Sansibar, only the first place being considerably north of the equator. This distribution is very hard to explain, as there are not only large distances by land, but wide stretches of sea between these places, so that the supposition of a gradual transport by man or animals does not help much. Transportation by means of aquatic birds, if possible, must be extremely rare while the supposed landconnections in former geological periods can hardly furnish a satisfactory explanation. At any rate, it seems very wonderful that the same type should have kept true over such distances and through countless generations while other phyllopods seem to have formed not only varieties but many new species and even genera. Auszug aus obiger Mitteilung; Am 19ten Juli 1928 fand der Autor in der Naehe von Natal, Hauptstadt des brasilianischen Staates Rio Grande do Norte, bei ca. 5º 47' suedlicher Breite, einen neuen Dendrocephalus, der, wegen seiner brillant scharlachroten Schwanzanhaenge, ornatus genannt wurde. Das Weibchen (Tafel 1) wird ca. 12 mm. lang und zeigt in seinem Bruetsack schwarze Eier; das Maennchen ist 16 mm. lang und bedeutend dicker. Seine zweiten Antennen, die auf Tafel 2 vor den ersten sichtbar sind, erreichen wohl den hoechsten Grad von Complizirtheit, der bisher abgebildet wurde und sind fuer die neue Art charakteristisch. Sie and sich in dem lehmigen Wasser einer grossen und tiefen Pfuetze an feinem Strassenrande. Die mitgenommenen Exemplare starben allmaelig ab und die Pfuetze trocknete spaeter aus. Die zweite Art (9-7-28 in Natal beobachtet) war eine Cyclestheria, sehon frueher in Matto Grosso und Paraguay gefunden und mit hislopi BAIRD identificirt. THIELE meint, dass vielleicht die brasilianische Art als sarslana abgetrennt werden sollte, indessen spricht die Vergleichung der Originalien und unabhaenger Zeichnungen nicht dafuer. Es ist eine hoechst auffaellige Tatsache, dass das Vorkommen dieser Art ausserdem in Vorderindien, Ceylon, Australien (Queensland), Celebes, Ostafrika und Sansibar festgestellt wurde und zwar nur einmal ziemlich weit noerdlich vom Aequator. Die Erklaerung dieser Verbreitung stoesst auf die groessten Schwierigkeiten, da zwischen den einzelnen Lokalitaeten weite Meere liegen und nicht bloss Landstriche, in denen die Art uebersehen werden koennte. Transport durch Menschenhand kann fuer groessere Strecken kaum in Betracht kommen und ein solcher durch Wasservoegel muesste jedenfalls ein sehr seltenes Ereigniss sein. Die Erklaerung der Verbreitung ueber hypothetische, in frueheren geologischen Perioden vorhandene Landbruecken ohne Veraenderung der Art kann ebenfalls kaum befriedigen. In allen Faellen kann man sich nur darueber wundern, wie, ueber solche Strecken und durch zahllose Generationen, derselbe Typus festgehalten wurde, waehrend sich bei anderen Phyllopoden nicht bloss Varietaeten, sondern neue Arten und sogar Gattungen gebildet haben.

Autonomous temperature data loggers were used to measure the temperature profile within a growing ice cover and in the water below. The ice formed under natural conditions over the pond. We observed the presence of distinct layers of gas bubbles throughout the ice thickness. Temperature measurements allowed us to determine growth rates (μm s−1) and cooling rates (°C s−1) of the ice and demonstrated that these bubble layers formed during the peak ice growth rates from 0.58 to 0.92 µm s−1. The growth rates, leading to the formation of layers of bubbles, were more than an order of magnitude lower than for bubbles produced in controlled laboratory conditions (from 3 to 80 µm s−1). This observation introduces the possibility that solid impurities play a role in natural waters and that they must lower the limit of growth rates required for bubble occurrence. Data revealed a decrease in ice growth rates while cooling rates increased. We interpret this observation as an effect of the heat flux from the water to the ice (8.34–34.11 W m−2), and of gas concentration changes in the water below. Calculations of the ice thickness using traditional methods showed the necessity to include the heat flux from the water to the ice and the effect of gas bubbles within the ice and near the ice–water interface.

In natural ponds, adult Notophthalmus virdescens prey on developing eggs of Ambystoma tigrinum. Predation by Notophthalmus was strong enough to exclude larval Ambystoma from one natural pond. Experiments conducted in artificial ponds demonstrated that the presence of Notophthalmus depressed mean mass at metamorphosis of surviving Ambystoma larvae. In turn, the presence of large Ambystoma larvae depressed eft production by Notophthalmus. Variation in density of adult Notophthalmus was not related to growth of adults and larvae, or eft production. Adult survival was depressed at high levels of adult density. Growth of adults and larvae was negatively correlated with larval density, suggesting competition between subpopulations in these two phases of the newt life cycle.

Larvae from seven full sib families of Hyla gratiosa were reared in experimental enclosures in a natural pond, while additional larvae from those families were raised in the laboratory. The sibships displayed different average levels of survival in the enclosures. The level of survival in an enclosure was positively correlated with the average body size of the enclosed larvae, and this size varied significantly among sibships in concordance with the variation in survival. Significant differences were found among sibships in the body sizes of larvae grown in the laboratory. Survival also varied significantly among the sibships in the laboratory, but was uncorrelated with either field survival or laboratory growth. Relative growth differences among sibships were consistent between laboratory and field conditions, although the extent of such variation was increased under field conditions. The positive correlation between average size and survival in the enclosures was interpreted as the result of size-limited predation by insects. Variation in growth among laboratory-reared sibships was interpreted to be a conservative assay for phenotypic variability under field conditions.

time, not only in P. alpinum, but in other species of the genus, and has led in one case at least, in South Africa, to the erroneous record of Dendroligotrichum as occurring there. Climacium dendroides (L.) Web. & Mohr.-Bear Id.; 17 June, V. S. Summerhayes (4b). Berggren records a single stem only, from King's Bay. Thuidium abietinum (L.) B. & S.-One or two gatherings were made of this. Berggren records it only from Green Harbour and Advent Bay. Amblystegium serpens (L.) B. & S.-Bear Id.; 17 June, V. S. Summerhayes (79). Sterile: not previously recorded from Spitzbergen. Calliergon sarmentosum var. fontinaloides Berggren.-Cape Boheman; 15 July, V. S. Summerhayes (IIoa). The exact habitat of this remarkable form is not given, but I have no doubt it was a submerged form. It appears to conform very fairly with Berggren's description of his var. fontinaloides (of which I have seen no specimens)' from the Dovre, Norway, but is, I should judge, a still more extreme form. The stems are 15 cm. long, very closely and regularly pinnate with short, subequal, widely divergent, elongate, much attenuated leaves.. The plant has, in fact, in almost every particular (except that the leaves are straight, not falcate) the appearance of a Drepanocladus such as D. Rotae, and it is hard to convince oneself, even when examining it with the lens, that it is not that, but a Calliergon. The lower part of the stem and the lower branches are much denuded, which appears to indicate a station in flowing water. The variety has only been recorded-from the high alps of Styria in addition to the original locality. I have a somewhat similar form from New Zealand, collected by Dr. L. Cockayne "on bottom of shallow natural pond in Craigieburn Mts., Canterbury, at 1200oo m. alt. " NORTHAMPTON, ENGLAND

The electrical properties of the two membranes, plasmalemma and tonoplast, bounding the cytoplasm of ' the brackish water characean, NitellopBiB obtUBa, were studied. In a solution approximating the natural pond water, the electrical potential difference between cytoplasm and outside was -141 mY, and between vacuole and cytoplasm +19 mY. The resistance of the plasmalemma was 80,000 n cms, and of the tonoplast, 10,000 n cm2