bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diet and predation by three leaf‐associated stoneflies (Plecoptera) in an Arkansas mountain stream
Authors: FEMINELLA JACK W. , STEWART KENNETH W. 
Published: May 2006

SUMMARY. 1. Life cycles, food habits, mouthpart morphologies, prey preferences, and predator‐prey size relationships were investigated for the three most common stoneflies in leaf packs in the Little Missouri River, Arkansas: Clioperla clio (Newman), Isoperla namata Prison, and Perlesta spp. Each species was univoltine and had a fast seasonal cycle, with extended egg or nymphal diapause, rapid nymphal growth and emergence in spring to early summer.2. Foregut analysis showed predictable dietary shifts by C. clio and Perlesta spp., from detritus and diatoms in early instars to invertebrate prey in later instars. Isoperla namata fed facultatively on insects, detritus and diatoms, with no conspicuous ontogenetic shifts. The mouthparts of all three species strongly reflected their diet.3. Electivity analysis indicated opportunistic feeding by the three species, with feeding rarely differing significantly from random.4. Sizes of stonefly predators and their ingested prey were highly correlated (P<0.01). However, rather than shifting toward larger prey sizes, growing predators expanded their size thresholds and continued to include numerous small prey items in their diet. Prey choice was governed most directly by prey availability, because stoneflies selected the most abundant groups, irrespective of size or taxon.5. The likelihood of competition among the three stoneflies for prey was minimized by timing of their life cycles, differential food use and probably the temporary nature of leaf pack habitats.
Variations in carbon fractions within a dimictic and a meromictic basin of the Junius Ponds, New York
Authors: PENDL MICHAEL P. , STEWART KENTON M. 
Published: May 2006

SUMMARY. 1. The Junius Ponds, a unique series of proximate glacial kettle basins located between the cities of Rochester and Syracuse. New York, U.S.A., contain basins of dimictic and meromictic nature. This study focused upon differences in partitioning of total inorganic carbon (TIC), paniculate organic carbon (POC), and dissolved organic carbon (DOC) within the dimictic Junius Pond 7 (JP7, ∼8m) and the meromictic Junius Pond 5 (JP5, ∼17m).2. For TIC, variations with depth were much greater in JP5 than in JP7. However, seasonal variations were greater in JP7 than in JP5. We attribute these variations to differences in the mictic nature of the basins.3. Concentrations of POC were substantially less in the relatively clear mixolimnion of JP5 than in the epilimnion of JP7. Distinct POC layers formed at the oxic‐anoxic boundary in both basins during late summer.4. The lower monimolimnion of JP5 is believed to have the warmest water occurring under ice (8.2–8.6°C) of any natural body of water in the continental United States east of the Mississippi River. The monimolimnetic region of JP5 has unusually low DOC:POC ratios of ≤1:l.
Suspended bacteria in calcareous and acid headstreams: abundance, heterotrophic activity and downstream change
Authors: RIMES CARRIE A. , GOULDER R. 
Published: May 2006

SUMMARY. 1. Concentration of total suspended bacteria and heterotrophic activity (as turnover rate and turnover rate per bacterium for glucose assimilation by a trace‐addition approach) were determined at distance intervals along four high‐trophic‐status calcareous headstreams in the Yorkshire Worlds and along four low‐tropic‐status acid headstreams in the Galloway Hills.2. Mean concentration of suspended bacteria was marginally greater in the calcareous streams while turnover rate and turnover rate per bacterium were substantially greater.3. Further determinations of heterotrophic activity (as turnover rate, turnover rate per bacterium, Vmax and Vmax per bacterium for glucose mineralization by a kinetic approach) supported the conclusion that heterotrophic activity was greater in the calcareous streams.4. Mean cell volume of suspended bacteria, measured by electron microscopy, was found to be greater in the calcareous streams.5. In the calcareous streams the concentration of total bacteria and turnover rate usually increased substantially, in a straight‐line relationship, with distance downstream from the source. In the acid streams such downstream increase was less usual, the rate of increase per unit length of stream was less, curvilinear relationships were more frequent and on some occasions downstream decrease was observed.6. The calcareous and acid streams thus formed two distinct groups on the basis of heterotrophic activity, cell volume and rate of downstream increase of suspended bacteria. This division was not necessarily caused solely by difference in pH but might be due to the combined effects of the many environmental variables which change in parallel with pH.
Species segregation during predator evasion in cyprinid fish shoals
Authors: ALLAN JOHN R. , PITCHER TONY J. 
Published: May 2006

SUMMARY. 1. When a predator attacks a mixed‐species group, individual prey arc faced with a conflict between retaining the advantages of large group size and the disadvantages of remaining among aliens. Experiments were designed to show how this conflict is resolved in fish shoals.2. Simulated attacks with a model predator were made upon mixed and single species shoals of three cyprinid species under semi‐natural conditions in a fluvarium.3. Measurements of elective group size, neighbour identity and distance, and encounters within and between species revealed behaviour which sorted fish into species at the onset of predator attack.4. A control experiment demonstrated the same effect for fish of matched size.5. The value to the individual of segregative behaviour in response to predator threat is discussed.
Fish communities in the perennial wetland of the Sudd, southern Sudan
Authors: HICKLEY P. , BAILEY R. G. 
Published: May 2006

SUMMARY. 1. Cyperus papyrus and Typha domingensis swamps were recognized as the major ecological zones in the perennial wetland of the Sudd.2. Fish sampling, chiefly by gill‐netting and electric fishing, was concentrated in the open‐waters of channels and lakes together with submerged, fringing and marginal vegetation in the accessible papyrus zone. Sixty‐two species were recorded including fifteen catfishes. thirteen characoids, seven cyprinids, seven mormyrids and seven cichlids.3. The highest diversity and abundance of tishes was obtained in the shallow Sudd lakes which revealed considerable uniformity in population structures. The most numerous species in gill‐nets were Alestes dentex, Synodontis frontosus and S. schall, whereas Heterotis niloticus, Mormyrus cashive and Distichodus rostratus assumed importance in terms of biomass. Micralestes avutidens and cichlids were abundant among the small fishes inhabiting fringes of Eichhornia crussipes, and air‐breathing species occurred beneath the vegetation mat.4. Flowing‐water habitats exhibited a similar but restricted fauna. Catches were dominated by Synodontis frontosus in open‐water and by Micralestes acutidens and Chelaethiops bibie in the margins. The latter species was shown to have a clear preference for running water.5. Peak catches in a representative river‐lake could be interpreted as the arrival of fish for breeding or their migration through the lake for reproduction elsewhere. The capture of fry or juveniles of many species in fringing or marginal vegetation indicates that the permanent floodplain of the Sudd provides suitable spawning and rearing grounds.6. Access to the extensive Typha zone was limited but from available evidence it was inferred that air‐breathing fishes, notably Heterotis and Gymnarchus, may penetrate the swamps to reach areas remote from perennial transmission channels.
A new window trap used in the assessment of the flight periods of Chironomidae and Simuliidae (Diptera)
Authors: JÓNSSON ERLENDUR , GARDARSSON ARNTHÓR , GÍSLASON GÍSLIMÁR 
Published: May 2006

SUMMARY. 1. A window trap is described which has been found useful in the study of the fight periodicity of chironomids and simuliids. the trap is simple to construct and can be operated in high winds.2. Window traps were operated in 1977 and 1478 at Lake Myvatn. Iceland, when thirty‐nine chironomid species and two simuliid species were caught. Most of the chironomids had two peaks in flight activity per year. e.g. Eukiefferietla minor, Cricotftpus tibialis. Pogonocladius consohrinus, Tanytaraus gracilentus and Micropsectra airofasciata. Chironomus islandicus and Heterotrissocladius grimshawi had one peak in activity in all traps. The flight activity of Prodadius istandicus, Orthocladius oblidens and Micropsectra Undrothi varied greatly between traps and years. Simulium vittatum had two peaks in flight activity, corresponding to the two generations developing per year. Variation in trap catches of .S. vittatum reflected populalion changes measured independently in a study of larval population dynamic
Production of the chironomid Procladius bellus in an annual drawdown reservoir
Authors: SEPHTON THOMAS W. , PATERSON COLIN G. 
Published: May 2006

SUMMARY. 1. In Laurel Creek Reservoir. Ontario, a small, eutrophic annual drawdown reservoir, some individuals of the chironomid Procladius bellus survive the winter drawdown.2. With refilling of the reservoir in spring, colonization by P. bellus is continuous and there were three generations a year.3. Production estimated by the size‐frequency method was 117.12 kg (175 mg m−2) in 1980 and 70.14 kg (105 mg m‐2) in 1981. Annual P:B was about 13 in both years.4. Substantial slation‐to‐station variations in production occurred and overall production was lower than in shallow habitats.
Phosphorus inactivation in a eutrophic lake by the direct addition of ferric aluminium sulphate changes in phytoplankton populations
Authors: FOY R. H. , FITZSIMONS A. G. 
Published: May 2006

SUMMARY. 1. Reduced total phosphorus concentrations in the summer which followed the addition of iron aluminium sulphate to White Lough failed to reduce significantly the phytoplankton. which continued to be dominated by Oscitlatoria agardhii var. isothrix Skuja.This species was present throughout the 4 years studied, forming over 50% of the algal volume in 80% of samples. In contrast, species which occurred principally in the summer months were found to be severely curtailed when sediment release of phosphorus was suppressed.2. The phosphorus: carotenoid ratio was used to assess the extent of phosphorus limitation because laboratory studies on O. agardhii var. isothrix showed that this ratio was a much beter indicator of cell phosphorus content than the phosphorus: chlorophyll a ratio. Reduced summer phosphorus concentrations in White Lough caused a transition from intermittent to continuous phosphorus limitation rather than a proportional reduction in the summer phytoplankton.3. Reduced autumn grazing pressure by Daphnia hyatina Leydig allowed large algal populations to develop in the winters following phosphorus reduction despite a 50% decline in total phosphorus. The combination of increased winter phytoplankton and lower total phosphorus reduced soluble reactive phosphorus concentrations to less than 5,μg P l−1 which in turn curtailed the spring diatom pulse.
Variation in the C:P ratio of suspended and settling seston and its significance for P uptake calculations
Authors: UEHLINGER U. , BLOESCH J. 
Published: May 2006

SUMMARY. 1. In 1981–84 limnocorral (LC) experiments were performed in Lake Lucerne. Switzerland, to manipulate the planktonic community by varying P fertilization and by removing large zooplankton (with a 95 μm screen).2. The C:P ratios in both suspended and entrapped seston exceeded the ‘ideal’ C:P ratio of 106 proposed by Redfield, Ketchum & Richards (1963) when P was limiting algal growth.3. P fertilization could decrease the sestonic C:P ratio to 106 only when P did not limit algal growth; P additions far exceeding the P loading of eutrophic lakes were necessary to obtain this situation.4. Changes in epilimnetic C:P ratios were usually related to short‐ term changes in primary production, caused by variable in situ light conditions and turbulence, and subsequent variation in POC concentrations.5. Entrapped seston in the 95 μm‐filtered LCs showed C:P ratios slightly higher than those of suspended seston, indicating fast P release and slower C mineralization in the epilimnetic nutrient cycle.6. Removing large crustacean zooplankton enhanced epilimnetic P mineralization, and C:P ratios of entrapped seston in the 95 μm‐filtered LCs were increased.7 Detritus formed a relatively high proportion of the seston and amounted to more than two‐thirds of the measured POC concentration.8. Calculations of algal P uptake using information on sestonic C:P ratios and 14C uptake rates are questionable, as long as detritus cannot be separated from algae and net carbon uptake cannot be accurately measured.
Prey selection by juvenile cyprinids from running water
Authors: SCOTT ALASDAIR 
Published: May 2006

SUMMARY. 1. The juveniles of dace (Leuciscus leuciscus (L.)) and roach (Rtuihts rtuihis (L.)) and yearling minnows (Phoxtnus phoxinus(L.)) exhibited generally similar patterns of feeding behaviour and preferences for particular prey types.2. Factors affecting prey selection included predator and prey size, prey activity and environmental conditions.3. All three species preferred prey sizes approximately 0.6x their maximum gape.4. Prey motion was essential to induce attack, and prey were usually selected in proportion to their relative activities.5. Specialization on one prey type was observed in still water, and was always directed at the most active prey type. In flowing water no specialization was observed, and size selection was suppressed in the juvenile fish. Yearling minnows, however, were size selective in both still and flowing water.6. The presence of macrophyte cover did not significantly change the pattern of prey selection, but did reduce the predation rale.7. These results are discussed in the context of previous studies of prey selection and optimal foraging.
Response of the freshwater marsh species, Panicum hemitomon Schult., to increased salinity
Authors: PEZESHKI S. R. , De LAUNE R. D. , PATRICK W. H. 
Published: May 2006

SUMMARY. 1. Panicum hemitomon Schult. plants were colleeted from Louisiana's Mississippi River deltaic plain freshwater marsh and subjected to salinities of 5–12 ppt under controlled environment conditiotis.2. The condition was designed to simulate salt stress resulting from storm surges, brine spills associated with oil recovery operations and salt water intrusion due to rapid subsidence and parallel increases in apparent sea level in Louisiana's coastal areas.3. Plant stomatal conductance was reduced between 55 % and 80% and net photosynthesis declined between 20% and 67% in response to the different salinities within 1 day of salt application. Both responses lasted throughout the entire experiment.4. Salinities ranging between 10 and 12 ppt resulted in tissue death in the plants 4 days after salt exposure.5. In addition to the short‐term impact of salt water influx on gas exchange of P, hemitomon reported here, the potential long‐term effects on habitat change are discussed.
Distributional patterns of immature Simuliidae (Diptera) in northwestern North America
Authors: CORKUM LYNDA D. , CURRIE D. C. 
Published: May 2006

SUMMARY. 1. Major landscape features and hydrological parameters indicative of black fly species assemblages were examined at 101 stream sites in Alberta, northern British Columbia, the Yukon and Alaska during the summer. Forty‐one black fly taxa were recorded at seventy‐ nine sites using qualitative sampling procedures. River sites lacking black flies had significantly higher conductivity, greater depth, shallower slope and were farther from the Pacific Ocean than sites with black flies.2. Classification of sites by taxon occurrence using hierarchical cluster analysis suggested five groupings: A. Simulium tuberosum(Lundstrëm) complex + several taxa. B, S. venustum Saylverecundum Stone and Jamnback complexes +S, tuberosum complex; C. 5. arcticum Malloch complex +S. corbis Twinn complex; D, Gymnopais Stone/Prosimulium Roubaud; and E. P. onychodactytum Dyar and Shannon complex + several taxa.3. Multiple discriminant analysis (MDA) was used to predict group membership of the seventy‐nine sites using nineteen environmental variables; 71% of the sites were classified correctly. MDA identified latitude and distance from stream source as important factors separating group D from other groups. Stream width and drainage basins entering the Arctic Oeean and Hudson Bay delineated group B. There was no clear separation among groups A. C or E. The presence of sibling species probably accounts for the overlap of black fly assemblages.4. Our findings are briefly discussed in the context of stream classification systems, notably the river continuum concept.
A comparison of chlorophyll a and carotenoid concentrations as indicators of algal volume
Authors: FOY R. H. 
Published: May 2006

SUMMARY. 1. Carotenoid concentration, as measured hy absorbance at 480 nm. was a better indicator of algal volume than chlorophyll a when the results from two lakes and laboratory studies on Osciltaloria agardhii var. isothrix Skuja were compared. The correlation between algal volume and carotenoid in White Lough (r=0.91) was significantly higher (0.001 P<0.01) than ihat between algal volume and chlorophyll a(r=0.77). The Lotigh Neagh correlation coefficient lor algal volume with carotenoid (r=0.89) was only marginally stronger than that with chlorophyll a(r=0.87).2. The relatively weak correlation between algal volume and chlorophyll a in White Lough was a result of a summer decline in the chlorophyll a content of O. agardhii var. isothrix, which dominated the phytoplankton. The chlorophyll a content of the phytoplankton was depressed by high summer daily totals ol light hours received by the phytoplankton in White Lough of up to 14 h in comparison to a maximum value of 3.8 h in Lough Neagh. where no seasonal cycle of chlorophyll a content was evident.3. Laboratory studies demonstrated that while chlorophyll a per unit algal volume of O. agardhii var. isothri.x declined with increasing light dose, carotenoid content did not. Nitrogen and phosphorus limitation depressed the carotenoid content but to a lesser degree than was observed for chlorophyll a.
Zooplankton populations and the diets of three Chaoborus species (Diptera, Chaoboridae) in a tropical lake
Authors: HARE LANDIS , CARTER JOHN C. H. 
Published: May 2006

SUMMARY. 1. Zooplankton populations in a small, natural, tropical lake are dominated by a few, small‐sized taxa including the copepod Thermo‐ cyclops consimilis, the cladoceran Moina micrura and several rotifer species.2. Moina micrura and adults of Thermocyclops consimilis undergo diel vertical migrations within the water column. Population densities of T. consimilis show marked intra‐annual variations which may to some extent be related to variations in rainfall and to lunar periodicities In predator abundance.3. The diets of Chaoborus lavae include other Chaoborus, Cladocera, Copepoda. Rotifera and the dinoflagellate Peridinium. The diets of late instars of the largest species, edulis, were dominated by Crustacea, while those of the two smaller species. C, ceratopogones and C. anomalus, were dominated by Rotifera and the dinoflagellate alga Peridinium, as were the diets of early instars of all species. Algae have not been previously reported to be a large component of the diet of Chaoborus populations in nature.4. Some of the dietary differences among Chaoborus instars and species are related to the size of each prey species in relation to the mouth gape of each instar. However, there are also important differences in electivity among instars of different species of the same size.
Time‐course of inorganic nitrogen uptake and incorporation by natural populations of freshwater phytoplankton
Authors: PRISCU JOHN C. 
Published: May 2006

SUMMARY. 1. Time‐course measurements of NH4+ and NO3−uptake were made on the natural phytoplankton populations in a eutrophic lake at a time when these nutrients were at their lowest annual concentration.2. Both NH4+ and NO3− uptake was increased at least five‐fold during the first 5 min of incubation following near saturating pulses of these nutrients.3. Elevated uptake was also observed following low level (∼2μg N 1−1) pulses of NH4+ and NO3−, but substrate depletion during the first hour of incubation may have been partially responsible for this apparent enhancement.4. Incorporation of I5N into TCA‐insoluble material (protein) following the saturating NH4+ pulse was increased less than total cellular 15N uptake, whereas no elevation of 15N incorporation into protein was observed following a saturating NO3−pulse.5. The percentage of I5N incorporated into protein, with respect to total cellular uptake, was ∼32% and ∼12% for NH4+ and NO3−, respectively, following 5 h of incubation.
Regulation of damseifly populations: the effects of larval density on larval urvival, development rate and size in the field
Authors: BANKS MICHAEL J. , THOMPSON DAVID J. 
Published: May 2006

SUMMARY. 1. The popuhttion density of Coenagrion pttella larvae was monitored in five populations, and of Ischntira elegans in two populations, between October 1982 and May 1983.2. There was no measurable mortality of larvae over winter and no larval growth until April. Larvae in high density populations were smaller than those in low density populations and were more likely to have a semi‐ voltine life history.3. The population density of C. ptiella was also monitored (more frequently) in two populations with differenl initial densities between July and November 1983. In the high density population there was a constant rate of larval mortality, while in the low density population there was no detectable larval mortality, indicating that larval mortality may be density dependent. Larvae in the high density population were again smaller, and more likely to be semi‐voitine, than those in the low density population.4. The role of density dependent larval growth, development and mortality in the regulation of damseifly populations is discussed.
Methods for the activation of the resting eggs of Daphnia
Authors: SCHWARTZ STEVEN S. , HEBERT PAUL D. N. 
Published: May 2006

SUMMARY. 1. The conditions required to initiate development of resting eggs of thirty‐six clones of Daphnia representing seven species were investigated.2. The temperature of both dark incubation and subsequent light treatment are shown to affect hatch success. By varying these parameters the majority of resting eggs from each test clone were stimulated to develop. Arctic clones required a low hatching temperature (7°C), whereas clones from warmer climates hatched best at 14–21°C.3. Variation in hatching cues existed between conspecific individuals from different collection sites. These differences suggest that research determining macro‐ and microgeographic patterns in hatching phenology would be fruitful.