bluuebunny/crossref_metadata_2025_split huggingface dataset:
A laboratory study of predator‐prey interactions of stoneflies and mayflies
Authors: WILLIAMS D. DUDLEY 
Published: May 2006

SUMMARY. 1. Reactions of individual predatory stoneflies to contact by individual mayfly prey, and vice versa, were studied in the laboratory using two sets of species, one from a stream in southern Ontario. Canada, and the other from a stream in North Wales.2. Based largely on information received via their antennae, the stoneflies were capable of distinguishing between conspecifics and mayfly prey and between prey species. A clear preference for certain prey species was evident but less preferred species were made more attractive when damaged or when the stoneflies were very hungry. Detection of conspecifics by stoneflies was confused in the presence of prey or the local smell of prey body fluids and this led to interference during hunting and feeding at high predator densities.3. Some mayfly species were capable of distinguishing between conspecifics. other mayflies and predators. The cerci were important in intra‐ and interspecific contact encounters between mayflies and were used in a fencing fashion to establish a minimum distance between nymphs. However, the cerci did not appear to play an anti‐predation role as stoneflies captured and ate mayflies with and without cerci in equal numbers.4. Reactions to conspecifics by the Palaearetie mayflies Rhithrogena semicolorata (Curt.) and Baetis rhodani (Pictet) were similar to those of the ecologically‐equivalent Nearctic species Stenonema vicarium (Walker) and Baetis vagans McDunnough.5. In encounters between mayflies, intra‐ and interspecific responses were similar. However, the responses of some mayfly species to conspeeifics were modified in the physical presence of a predator or the water from its holding tank. Different mayfly species made specific responses to predaeeous stoneflies. Responses to a herbivorous stonefly were either similar to conspeeific encounters or were intermediate between them and encounters with predators.6. Experiments to reveal the exact nature of the stonefly stimulus detected by the mayfly nymphs strongly suggested that there were two components to the stimulus. One was physical contact by the predator's antennae, the other was chemical in nature and could be detected only over short distances (up to a few mm). Independently each could elicit a response, but combined their effect appeared to be synergistic.7. Different mayfly species responded differently to the stonefly Phasganophora capitata (Pictet) and this sequence of sensitivity was mirrored by the predator's choice of prey species—the most sensitive to the predator being the favoured prey and the less sensitive the least favoured. The significance of these findings to optimal foraging theory, as applied to tactile predators, is discussed.
The distances travelled by downstream‐moving trout fry, Salmo trutta, in a Lake District stream
Authors: ELLIOTT J. M. 
Published: May 2006

SUMMARY. 1. Field experiments were performed in the day and night at six modal water velocities (range 10–52cm s−1), using: (i) newly‐ emerged fry without neutral buoyancy; (ii) older fry in poor condition (weight well below that expected for resident fry); (iii) older fry in good condition (weight similar to that of resident fry); (iv) dead fry.2. An exponential model described the return rate of fry to the stream bottom; the mean distance travelled downstream varied considerably between the four fry categories, but always increased linearly with increasing water velocity.3. Results were similar for dead fry and newly‐emerged fry released at night; 50% of the fry returned to the bottom in 10–11 s and nearly all returned in c. 70s, the maximum distance travelled ranging from c. 7 m at 10 cm s−1 to c. 37m at 52cm s−1, Newly‐emerged fry released in the day returned slightly faster (54s for 99% return to bottom).4. Older fry in poor condition returned to the bottom slightly faster in the day than at night, but took about 2 min and travelled about twice the distance covered by dead fry. Older fry in good condition returned to the bottom at the fastest rate (3–6s for 50% and c. 30s for the rest), and travelled only about half (at night) or a third (in day) of the distance covered by dead fry.5. The implications of this investigation are discussed and it is concluded that, apart from water velocity, the age and condition of the fry were the two most important factors affecting their downstream movement.
Colonization and ecological development of new streams in Glacier Bay National Park, Alaska
Authors: MILNER ALEXANDER M. 
Published: May 2006

SUMMARY 1. Colonization and ecological development of postglacial freshwater communities was investigated in Glacier Bay National Park, south‐eastern Alaska, following the rapid recession of a Neo‐glacial ice sheet within the last 250 years.2. Environmental variables shown to be most significant in stream development were temperature, flow regime and sedimentation.3. The Chironomidae (Diptera) were the pioneer invertebrate colonizers of newly emergent streams arising as meltwater from receding ice sheets and displayed a distinct pattern of succession with stream maturity.4. Ephemeroptera and Plecoptera colonized warmer clearwater streams, but Trichoptera had a minimal role in invertebrate community development.5. Establishment and production of salmonid fish populations in the new streams related principally to stream flow and sediment characteristics.6. Future pathways along which the streams may develop is probably dependent on the degree of large organic debris input.7. Stream development, structure and function are summarized including reference to theories of ecosystem development, ecological succession and community stability.
Relationships between bathymetry, water quality and diatoms in some Hebridean lochs
Authors: FLOWER R. J. , NICHOLSON A. J. 
Published: May 2006

SUMMARY 1. Computer methods for mapping and calculating morphometric characteristics are described and applied to seventeen previously unsurveyed South Uist lochs.2. Deposited sea salt is shown to have a major effect on water quality and the effect varies according to distance from the west coast. Calcium concentrations appear to be determined by dissolution of locally abundant shell debris. Sulphate and particularly nitrate concentrations are influenced significantly by catchment sources.3. Surface sediment diatom assemblages from all seventeen sites are analysed using multi‐variate methods (Hill, 1979). Assemblages are shown to be clearly distributed along DECORANA axis 1 and are clustered into five groups by TWINSPAN.4. Correlation analysis of water quality, morphometric characteristics, and DECORANA axes scores indicates that conductivity has the strongest influence on surface sediment diatom assemblage composition whereas morphometric characteristics have no demonstrable effect.
Temperature‐induced changes in the life cycle of Leuctra nigra(Plecoptera: Leuctridae) from a Lake District stream
Authors: ELLIOTT J. M. 
Published: May 2006

1. The life cycle of Leuctra nigra (Olivier) took 2 years in a small stream in the English Lake District and the exponential growth of the larvae was scarcely affected by variations in water temperature (range 4.2‐14.0°C). Mean growth rates for three year‐classes were 0.43±0.01, 0.42±0.01, 0.39±0.05% body length day−1. There were thirteen or fourteen larval instars for males and fourteen or fifteen for females. The ratio between successive instars was a constant 1.20 (conformed with Dyar's rule).2. Larval growth and mortality were exponential at six constant temperatures (5.9, 8.2, 12.1, 15.8, 18.2, 19.8°C) in the laboratory. Mean growth rates (% body length day−1) increased directly with temperature from 0.37 (5.9°C) to 0.55 (19.8°C). Mean mortality rates (% day−1) increased directly with temperature from 0.20 (5.9°C) to 0.26 (12.1°C) and then markedly increased to 0.54‐0.58 at the three higher temperatures. Only 7‐10% of animals completed their life cycle at the three higher temperatures compared with 23–27% at the three lower temperatures. Egg production also decreased considerably at the higher temperatures.3. As growth rates in the stream and laboratory were similar at similar temperatures (<14°C), the optimum conditions for growth in the laboratory were probably similar to those in the stream; therefore resources such as food and space were not restricting growth in the stream.4. The implications of the temperature‐induced changes in growth and mortality are discussed and it is concluded that although the life cycle can change from semivoltine to univoltine with increasing temperature, the costs of a univoltine life cycle are high in terms of survival and egg production, both of which decreased markedly between 12.1 and 15.8°C. Therefore the optimum habitat for this species appears to be a summer cool stream (maximum temperature <14°C) and the optimal life cycle appears to be about 2 years from egg to adult.
Resource utilization by the freshwater deposit feeder Ptychoptera townesi (Diptera: Ptychopteridae)
Authors: MATTINGLY ROSANNA L. 
Published: May 2006

SUMMARY 1. False crane fly larvae, Ptychoptera townesi (Diptera), occurred in high densities in a flow‐controlled section of stream where fine particulate organic matter (FPOM; 0.45 μm to 1 mm in diameter) had accumulated, but were quite rare both upstream and downstream from the section.2. In laboratory studies, P. townesi grew only on FPOM less than 250 μm. Larvae consistently grew fastest when fed small particles (0.45–53 μm in diameter).3. Ptychoptera townesi consumed relatively small amounts (0.002 mg per mg animal dry mass day−1) of FPOM (0.45–53 μm). They had long gut content passage times (greater than 19 h) and relatively high efficiencies of conversion of ingested food to body substance (20.7%). Gut content passage times were variable, and depended partially on the nature of the substrate.4. False crane fly larvae compacted FPOM into faecal pellets considerably larger in size than particles ingested. They lost mass when allowed to feed on their own faecal material, as well as on faeces greater than 250 μm in diameter produced by shredders. However, they survived and grew on shredder faeces (53–500 μm in diameter) that contained a mixture of smaller particles and particles too large for ingestion.5. The overall pattern of resource utilization by P. townes involved slow handling of relatively small volumes of food, which probably passed once only through a complex alimentary tract.
Population dynamics and production of five crustacean zooplankters in a subtropical reservoir during years of contrasting turbidity
Authors: HART R. C. 
Published: May 2006

SUMMARY 1. The temporal dynamics and demography of Meta‐diaptomus meridianus (Van Douwe), Lovenula excellens Kiefer. Daphnia gibba Methuen, D. barbata Weltner and Moina brachiata Jurine were studied for 2 years in a small bay of Lake le Roux (Orange River, South Africa). Total zooplankton biomass and population density were 1.4–3 times higher during the less turbid conditions of 1982/83 (Secchi depth transparency around 35 cm) than they were at around 25 cm Secchi depth during 1981/82, when D. barbata was absent.2. On average, instantaneous birth rates, rates of population change and death rates varied only slightly between years. Birth and death rates were considerably higher above 15°C than below 15°C. These rates correlated with one another and with zooplankton abundance both inter‐ and intra‐specifically suggesting that competitive interactions were important in population regulation. Mortality rates varied more strongly and consistently in a density‐dependent direction than did birth rates. In addition to depressed fecundity, the inferred survival of young was poor and population growth low, possibly because food shortage caused high post‐natal mortality.3. Estimates of annual production derived from finite birth rate values varied consistently with annual differences in biomass, and amounted to between 6 and 10 g m−2 y−1 dry wt. Annual P/B values varied from around 20 for the daphnids to 55 for the copepods and 75 for Moina. Apart from the latter, whose annual P/B ratio virtually doubled from 45 to 75 following reductions in turbidity, annual differences in P/B ratio were slight.
The behaviour and form of Psephenus herricki (DeKay) (Coieoptera: Psephenidae) in relation to water flow*
Authors: McSHAFFREY D. , McCAFFERTY W. P. 
Published: May 2006

1. Psephenus herricki (DeKay) larvae were observed in aquaria and artificial streams using videomacroscopic techniques. Dye visualization was used to determine flow around the organisms.2. The highly flattened larvae of Psephenus herricki are able to withstand and/or avoid the force of flowing water in streams through a number of mechanisms. The legs are vital: if they cannot gain purchase the larvae can be dislodged by the lifting forces acting on the body. At the flow rates tested (up to 50 cm s−1), suction under the carapace is not needed to maintain position.3. Active pumping of water through lateral slots of the carapace and out from under the body posteriorly greatly reduces turbulence around the body and may act to decrease drag at high Reynolds numbers.4. An interpretation of the flattened body‐shape of Psephenus herrickilarvae as an adaptation to fast currents and/or to prevent the larvae from being removed from the substrate by a predator is of questionable ecological significance because individuals are usually found in crevices and on the undersides of stones.
Levels of protein, RNA, DNA, glycogen and lipid during growth and development of Daphnia magna Straus (Crustacea: Cladocera)
Authors: McKEE MICHAEL J. , KNOWLES CHARLES O. 
Published: May 2006

1. Protein, RNA, DNA, glycogen and lipid content were determined in Daphnia magna on days 0, 2, 4, 6, 8 and 21 of growth and development. The composition of D. magna as percentage of reconstituted dry weight was similar to other zooplankton with the exception of DNA content, which was lower than values previously reported.2. The relative content of protein, RNA, DNA and reconstituted dry weight changed during the 21‐day growth period, and these changes were related to growth rate and total growth of D. magna. RNA:protein, RNA: reconstituted dry weight, and protein:RNA : DNA ratios were highly correlated to relative growth rate and total growth as measured by protein content or reconstituted dry weight.3. Addition of progeny biomass to adult biomass increased correlations between biochemical ratios and absolute growth rate, but had little effect on relationships involving relative growth rate or total growth.4. The relationship between biomolecule ratios and growth established for D. magna grown under optimal conditions was not successful in predicting growth of D. magna reared under crowded conditions.5. These data indicate that variation in biochemical ratios among life, stages of D. magna may be used to predict growth of organisms grown under similar conditions, but may not be extended to other situations. It is suggested, however, that variation in biochemical ratios in a particular life stage of a zooplankton species may be related to the productivity for that species.
Cladoceran birth and death rates estimates: experimental comparisons of egg‐ratio methods
Authors: GABRIEL WILFRIED , TAYLOR BARBARA E. , KIRSCH‐PROKOSCH SUSANNE 
Published: May 2006

I. Birth and death rates of natural cladoceran populations cannot be measured directly. Estimates of these population parameters must be calculated using methods that make assumptions about the form of population growth. These methods generally assume that the population has a stable age distribution.2. To assess the effect of variable age distributions, we tested six egg ratio methods for estimating birth and death rates with data from thirty‐seven laboratory populations of Daphnia pulicaria. The populations were grown under constant conditions, but the initial age distributions and egg ratios of the populations varied. Actual death rates were virtually zero, so the difference between the estimated and actual death rates measured the error in both birth and death rate estimates.3. The results demonstrate that unstable population structures may produce large errors in the birth and death rates estimated by any of these methods. Among the methods tested, Taylor and Slatkin's formula and Paloheimo's formula were most reliable for the experimental data.4. Further analyses of three of the methods were made using computer simulations of growth of age‐structured populations with initially unstable age distributions. These analyses show that the time interval between sampling strongly influences the reliability of birth and death rate estimates. At a sampling interval of 2.5 days (equal to the duration of the egg stage), Paloheimo's formula was most accurate. At longer intervals (7.5–10 days), Taylor and Slatkin's formula which includes information on population structure was most accurate.
What is cyclomorphosis?
Authors: BLACK R. W. , SLOBODKIN L. B. 
Published: May 2006

1. The history of the term cyclomorphosis and of research investigating the phenomenon it describes are reviewed briefly.2. Several distinct definitions of this term appear in the limnological literature. Some of these definitions are consistent with earlier studies; others are not and are very restrictive and reliant upon extensive laboratory analysis.3. We argue for the adoption of a broad definition of cyclomorphosis that is consistent with the majority of previous studies and practical to apply to the field populations it attempts to describe.4. We also urge all researchers investigating this phenomenon to provide their working definition of this term in their reports in order to avoid terminological confusion.
Spatial distribution of denitrifying activity in a stream draining an agricultural catchment
Authors: COOKE JAMES G. , WHITE ROBERT E. 
Published: May 2006

SUMMARY 1. A field study was made of the spatial distribution of denitrification activity in the sediment of the River Dorn, Oxfordshire, England.2. An assay of denitrifying enzyme activity was used to examine the distribution of denitrification with depth in cores of sediment representative of the types found in the stream. The maximum activity recorded in a predominantly silt sediment core was 5 times greater than that recorded in a sandy gravel core. In both fine sand and silt cores, peaks in denitrifier enzyme activity were shown to correspond to the limit of the nitrate diffusion front. At this depth the redox potential dropped rapidly from + 300 mV to 0 or less. Denitrifying enzyme activity in the stream water was negligible.3.In situdenitrification activity (I DA) measurements were carried out in an 800 m reach of the Dorn using the acetylene inhibition technique on small sediment cores. Concurrent measurements were also made of stream depth and velocity, nitrate concentration in the interstitial water, and the wet bulk density, loss on ignition, mineraliz‐ able carbon and total nitrogen contents of the sediment. Mineralizable carbon was the variable which showed the best correlation with I DA. Highest IDAs were associated with accumulations of fine‐grained sediment at meander bends. Mean IDAs measured under flood conditions were significantly higher (P<0.05) than those measured under baseflow. It was estimated that denitrification reduced the nitrate load in the River Dorn by 15% under summer baseflow conditions
The relation between wave exposure and distribution of emergent vegetation in a eutrophic lake
Authors: WEISNER STEFAN E. B. 
Published: May 2006

SUMMARY 1. Maximum water depth penetration and changes in horizontal distribution during 39 years of the emergent vegetation in a eutrophic lake in southern Sweden were investigated.2. The capacity of the emergent vegetation to penetrate into deeper water areas was found to be higher at wave exposed than al sheltered sites.3. Differences in biomass and biomass allocation of the dominant speeies. Phragmites australis, between an exposed and a sheltered site suggest that horizontal expansion towards deeper water at sheltered sites is limited by unfavourable substrate conditions.
Basis of selective predation by the aquatic larvae of the salamander,Ambystoma tigrinum
Authors: LEFF LAURA G. , BACHMANN MARILYN D. 
Published: May 2006

SUMMARY.1. The effect of several factors on feeding selectivity by three size classes of larvae ofAmbystoma tigrinum(Green) was examined. Five types of invertebrate prey were used:Chaoborus, Daphnia, damselflies,Hyalellaand water boatmen.2. Five variables were examined in relation to the electivity indices associated with each prey type: ease of prey consumption, ease of prey capture, relative prey size, prey activity, and microhabitat overlap. No single variable explained the observed electivity.3. For small larvae (snout‐vent length, SVL, <2.5cm) relative prey size was correlated with electivity. For large larvae (SVL >6.5cm), ease of prey consumption, prey activity, and relative prey size predicted electivity values. However, none of the measured variables was related to electivity values found for medium sized larvae (SVL >3.5 and <5.5cm).
Aspects of mating, reproduction, and co‐occurrence in three freshwater calanoid copepods
Authors: CHOW‐FRASER PATRICIA , MALY EDWARD J. 
Published: May 2006

SUMMARY. 1. We examined the seasonal distributions and mating behaviour of Epischura lacustris, Diaptomus minutus and Diaptomus oregonensis to evaluate several proposed mechanisms for reproductive isolation. There was no divergence in onset of maturity or timing of breeding periods between sympatric diaptomid populations; size displacement between co‐occurring diaptomid species did not result in concomitant reduction in mating frequency between heterospecific pairs in the laboratory.2. Divergence in mating behaviour was supported by observations that, in conspecific mating experiments, males of both diaptomid species discriminated between females bearing ripened ovaries (gravid) and those that did not (non‐gravid), and that, in heterospecific trials, males either mated indiscriminantly with all females, or engaged in mating very infrequently.3. In mating experiments with Epischura. males did not discriminate between gravid and non‐gravid females, but mated exclusively with virgins of a specific relative size. Divergence in timing of breeding seasons between Epischura and the two diaptomid species suggests that even if mating between genera is possible, it does not occur often in nature.4. We discuss the adaptive significance of different reproductive strategies of these three copepods and speculate on mechanisms that allow for coexistence of the closely related taxa in nature.