bluuebunny/crossref_metadata_2025_split huggingface dataset:
The feeding relationships of two invertebrate predators in a New Zealand river
Authors: DEVONPORT B. F. , WINTERBOURN M. J. 
Published: May 2006

SummaryThe size frequency distributions and foods of the larvae of Archichauliodes diversus (Megaloptera: Corydalidae) and Stenoperla prasina (Plecoptera: Eustheniidae) were studied for a year in the Glentui River, South Island, New Zealand. These two species are the largest invertebrate predators inhabiting streams and rivers in New Zealand, where they are the only carnivorous members of their respective orders. Both species occupied the same habitat with A. diversus being slightly more abundant in most months. Many small larvae occurred within the sediments of the stream bed, whereas more larger larvae were found on stones lying on the surface. A wide size range of larvae was present throughout the year and the median size (in terms of head width) of both species was similar in most months. Larval growth could not be determined from field data and the life cycles of both species can be described as non‐seasonal. Quantitative sampling in 5 months provided estimates of population densities. These were maximal in December when values of 136/m2 for A. diversus and 114/m2 for S. prasina were obtained.Larval Chironomidae and mayflies of the genus Deleatidium were the most frequently taken prey of both predators in all months, and no strong relationship between size or species of predator and size of prey was found. Caseless trichopteran larvae formed a less important component of the diets of both species and detritus was ingested by some individuals. No instances of cannibalism and only one example of cross‐predation by each predator was seen. Diel sampling in November showed that large Deleatidium larvae were relatively more abundant in the guts of insect predators and in nocturnal drift samples than in the benthos. This suggests that their greater activity at night may increase their susceptibility to predation by nocturnal feeders.No clear ecological segregation of the two species with respect to habitat or prey utilization was found and there was no obvious interspecific competition for food, which appeared to be abundant at all times. Finally, the prevalence of non‐seasonal life cycles in New Zealand aquatic insects is discussed in relation to the low degree of speciation in several groups.
Assemblages ofPisidiumspecies (Bivalvia, Sphaeriidae) from localities in eastern England
Authors: BISHOP M. J. , HEWITT S. J. 
Published: May 2006

SummaryCollections of Pisidium spp, were made from a large number of sites and a diversity of habitats, The concurrence of the different species was examined, An ordination of the assemblages showed no marked clusters, but could be related to habitat.
Studies on Plover Cove Reservoir, Hong Kong
Authors: HODGKISS I. J. , TAI Y. C. 
Published: May 2006

SummaryThe species composition and year‐month frequency together with the abundance of the four periphytic communities of Plover Cove Reservoir (the epiphyton, epilithon, epipelon and epipsammon) were compared both in terms of all species present and in terms of major (dominant/frequent) species using the ‘circle’ method. All four communities were similar in terms of overall species composition but the richest variety of species occurred in the epiphyton. The diatom floras on wood and rock surfaces closely resembled each other as did the two sand grain floras. The former floras were, however, much more diversified than the latter floras and stood distinctly apart from them. In terms of their dominant/frequent species, the epipelic/epipsammic communities and the epiphytic/epilithic communities had the same number of common taxa (three), a further indication of the closeness between the two communities in each combination. On the other hand, the fact that the three common taxa were different for each combination again reveals the distinct differences between the two combinations.Investigations concerning the effect of the nature of the substrate on diatom growth revealed that it had little effect in qualitative terms. Quantitatively there would appear to be some effect, since differences in abundance and frequency and thus in the seasonal cycle of diatoms growing on different substrates were observed. The conditions in the microhabitats of each substrate undoubtedly determined the dominance and abundance of the flora. However, the effect of the nature of the various substrates on diatom growth varied from species to species and in general, the substrates showed little qualitative selectivity. Thus, no truly differential species were found to any great extent on any of the four substrates.The relationships between the growth of these four periphytic diatom communities and the physical and chemical conditions have also been investigated in terms of cell number and chlorophyll content. Both graphical and statistical analyses of the results are discussed, and it is suggested that fluctuations in water level, temperature and nutrients (especially silica, nitrate and phosphate) are the major factors governing the seasonal patterns of variation in periphyton standing crop. Thus, diatom growth is maximum when nutrient concentrations and water level are high and when water temperature is low, and as temperature increases and nutrients decrease so diatom growth falls. It is probable that an interplay of these factors, together with the detrimental effects of heavy rainfall and typhoons during summer, is responsible for the seasonal changes in periphyton in Plover Cove Reservoir exhibiting a winter peak as opposed to the commonly occurring spring and autumn growth peaks.
Studies on Plover Cove Reservoir, Hong Kong
Authors: HODGKISS I. J. , CHAN L. T. H. 
Published: May 2006

SummaryThe zooplankton fauna of the Plover Cove Reservoir has been investigated using two sampling series. The first series involving a 3‐year investigation using 6‐ft vertical hauls at three stations in the reservoir, revealed the presence of two copepod and four cladoceran species with little variation in terms of seasonal peak occurrence and abundance in any of the stations and so no evidence of the horizontal distribution patterns referred to by other authors. In all three stations Diaptomus gracilis was the dominant copepod species and Diaphanosoma leuchtenbergianum the dominant cladoceran species.The second series, involving a 13‐month investigation of vertical sets of water samples collected both day and night at 4‐h intervals for 24‐h periods, revealed that in terms of seasonal vertical distribution, all six species occurred at all depths during the survey, but with a tendency to be concentrated in the surface waters.In terms of diurnal vertical distribution, differences in the migration pattern occurred from season to season in the case of Diaptomus gracilis. Thus, during spring, summer and autumn, concentrations occurred at the surface at 10.00 and 22.00 hours followed by migration to greater depth, whereas in winter, surface accumulations persisted even into the daylight hours. However, both Cyclops hyalinus and Diaphanosoma leuchtenbergianum showed surface accumulations at night and a movement away from the surface by day during all seasons.Investigations of the seasonal variation in environmental parameters conducted during both sampling series revealed that, as in the case of similar surveys, water temperature was the major controlling factor governing the seasonal variation in composition of the zooplankton fauna as well as its seasonal vertical distribution since in the case of Diaptomus gracilis and Ceriodaphnia reticulata low water temperatures corresponded with peak seasonal occurrence whereas in the case of the other species high water temperatures corresponded with peak seasonal occurrence, and since Diaptomus gracilis and Diaphanosoma leuchtenbergianum showed maximum concentration near the surface when surface water temperatures were high, whereas the remaining species showed their maximum concentration near the surface when lower water temperatures prevailed.It would also appear, however, that seasonal changes in zooplankton densities closely followed algal densities since Diaptomus gracilis, Diaphanosoma leuchtenbergianum and Bosmina longirostris had their maxima in late spring and Cyclops hyalinus in late summer while algal densities in this reservoir were highest in early spring and early summer.With regard to the diurnal vertical distribution of the zooplankton, light appeared to be the only factor alternating by an amount likely to be correlated with such diurnal vertical changes in zooplankton density.
Respiratory behaviour of larvae of four species of the Family Polycentropodidae (Trichoptera)
Authors: PHILIPSON G. N. , MOORHOUSE B. H. S. 
Published: May 2006

SummaryLarvae of Plectrocnemia conspersa and Polycentropus flavomaculatus from flowing water and Cyrnus flavidus and Holocentropus picicornis from still water were selected for study.In the above sequence, these larvae are associated with increasing ranges of temperature in their natural habitats. Experimental determination of lethal temperatures and investigations on ventilation frequency indicated that the larvae were increasingly tolerant of temperature in the same sequence of species.C. flavidus and H. picicornis showed infrequent ventilation which was little affected over wide ranges of temperature and dissolved oxygen but was stimulated erratically by water flow. P. conspersa and P. flavomaculatus showed more active ventilation which was more sensitive to changes in temperature and dissolved oxygen and was decreased by water flow.Consideration of ventilation in relation to oxygen uptake in P. conspersa and P. flavomaculatus suggests that ventilation activity may account for some 60–70% of active oxygen uptake. Differences in ventilation behaviour may thus be important in limiting larval distribution in stream systems.
Dominant diatoms in Tjeukemeer (The Netherlands)
Authors: MOED J. R. , HOOGVELD H. L. , APELDOORN W. 
Published: May 2006

SummaryA situation is described where silicon depletion affected a population of diatoms, mainly Diatoma elongatum and Melosira spp., in the shallow lake Tjeukemeer (The Netherlands). After Si‐deficiency the numbers of cells dropped quickly, whereas at least for the upper layer (0–1 m) a big increase in the percentage of biprotoplastic D. elongatum cells was observed. Probably the major part of the D. elongatum population arrived alive at the bottom. Heavy winds occurring 2 weeks later stirred up considerable numbers of both diatoms. The numbers of dead D. elongatum cells was then 40–50%, presenting some evidence that a large scale dying of D. elongatum cells occurs rather shortly after arrival at the bottom of Tjeukemeer. In the following weeks, at low Si‐concentration, numbers of D. elongatum almost doubled with once again a relatively high percentage of biprotoplastic cells, whereas numbers of Melosira spp. decreased. In the relevant conditions it seems that D. elongatum can take up silicon faster than Melosira spp.
Changes in the zooplankton of Lakes Mutanda, Bunyonyi and Mulehe (Uganda)
Authors: GREEN J. 
Published: May 2006

SummarySamples taken from Lake Mutanda in 1975 indicate that the specific composition of the zooplankton has changed from that in 1962. This change is very similar to that which occurred in Lake Bunyonyi sometime between 1931 and 1962. The most important aspect of the change is the disappearance of three species of Daphnia, together with Ceriodaphnia reticulata, Metadiaptomus aethiopicus, and Caridina nilotica. The 1975 samples indicate lower standing crops of zooplankton in all three lakes, and lower ratios of nauplii to copepodids than in 1962. The possibility of these changes being attributable to human activities is discussed.
Sediment development and its influence on the distribution and tube structure of Chironomus plumosus L. (Chironomidae, Diptera) in a new impoundment
Authors: McLACHLAN A. J. , CANTRELL M. A. 
Published: May 2006

SummaryField and laboratory evidence is presented to demonstrate that colonization of a new impoundment by the early invader, Chronomus plumosus L., is strongly influenced by sediment, the depth of which affects both larval abundance and tube shape. Larvae avoid areas with little sediment, such as eroded or newly inundated shores. In laboratory experiments, larvae constructed horizontal tubes in sediments between 3 and 10 mm depth, but in deeper sediments (11–30 mm) most of the larval tubes were vertically orientated. Of these about 70% were U‐shaped and the remainder J‐shaped. Larval abundance was positively correlated with sediment depth in the range 0–10 mm.
Decomposition of aquatic biota and sediment formation: lipid components of two blue‐green algal species and of detritus resulting from microbial attack
Authors: CRANWELL P. A. 
Published: May 2006

SummaryTo simulate early stages in the diagenesis of algal material in lakes, microbial attack was allowed to proceed on natural populations of two blue‐green algal species, Gloeotrichia echinulata (J. E. Smith) P. Richter and Oscillatoria agardhii var. isothrix Skuja. Changes in composition and abundance of the major lipid fractions were related to differences in the ease of microbial attack and to the effect of oxygen on the decay process. The loss of labile unsaturated compounds during diagenesis is consistent with the small amount of these compounds in most lake sediments.
Types of parasitism by larvae of water mites (Acari: Hydrachnellae)
Authors: BÖTTGER KLAUS 
Published: May 2006

SummaryThe larvae of Hydrachnellae can be divided into three types, based on the habits of the parasitic (larval) stage in the life cycle. (1) The larvae do not leave the water. Parasitizing aquatic insects, they are permanently submerged and wet. Only some species of the family Hydrachnidae belong to this type. (2) The larvae leave the water. The parasitic phase occurs either on insects living on the water surface, or in the air stores of aquatic insects. In both cases the larvae are not in direct contact with water during the parasitic phase. The Limnocharidae, Eylaidae and some species of the Hydrachnidae belong to this type. (3) The larvae parasitize insects which live in the air and which can leave the direct proximity to water; therefore it may be difficult for the mite larva to return to water. Except for the Hydrachnidae, Limnocharidae and Eylaidae, all families of the Hydrachnellae belong to this type.
Experiments on feeding and growth of the amphipod Gammarus pulex (L.) related to its distribution in the River Duddon
Authors: WILLOUGHBY L. G. , SUTCLIFFE D. W. 
Published: May 2006

SummaryIndividuals of Gammarus pulex were kept at 15°C for periods of 23–70 days on diets comprised of elm or oak leaves, Tricladium and Clavariopsis (Hyphomycete fungi), Molinia (grass), Zygogonium (alga), Nardia (liverwort). Both the mean interval between moults (mi), and daily increments in body wet weight, were related to diet. The lowest value for mi was 14·6 days on a diet of naturally decaying elm and oak leaves. The largest weight gains also occurred on this diet; the average daily gain in weight (Dw) = 130·8 μg/day, the mean specific gain in weight (Gw) = 1·69 μg %/day. On green Molinia and fungi diets Dw ranged from nil to 60·7 μg/day, and mi= 17·4–18·4 days was significantly (P<0·01) longer than mi on leaf diets. Survival and growth were poor on brown Molinia. Nardia did not support growth or survival. A mixed diet of Tricladium, Zygogonium, Nardia and decaying grasses was not sufficient to promote an increase in body weight, and mi= 21·8 days. This diet represents the commonly available food materials in Mosedale Beck, an acid stream in the upper Duddon catchment. Survival and growth of G. pulex on fungi and leaf diets in media containing low concentrations of potassium ions are also described and discussed briefly in relation to the distribution of G. pulex in the upper catchment of the R. Duddon.
Seasonal and diel periodicity in the drift of aquatic insects in a subtropical Florida stream
Authors: COWELL BRUCE C. , CAREW WARREN C. 
Published: May 2006

SummaryA study of insect drift was conducted in a small, subtropical Florida stream from December 1971 to December 1972 to describe the seasonal and diel periodicity and to determine factors influencing behavioural drift. Paired samples of 2 h duration beginning 15 min after sunset were taken biweekly, and hourly collections over a 24‐h period were made quarterly. Benthic invertebrates were collected on each date from three habitats (riffle, pool and aquatic vegetation) and temperature, dissolved oxygen and current velocity were measured.Drift rates ranged from 100 to 2125 organisms/m2. h (0·03 to 0·49 organisms/m3) and were greatest in winter and early spring; minimal rates occurred in the summer months. The following six taxa, in order of relative abundance, comprised 87% of the drift: Baetis intercalaris, Cheumatopsyche sp., Stenonema exiguum, Chironomidae, Stenelmis fuscata and Simulium sp. Total drift showed no significant correlation with temperature, dissolved oxygen or mean benthic abundance and only slight correlation with current velocity (r=0·34). Stepwise, multiple regression analyses indicated that riffle density and mean size of drifting organisms were important factors influencing the drift rates of B. intercalaris (R=0·67) and S. exiguum (R=0·82); mean size, riffle density and water temperature influenced the drift of Cheumatopsyche sp. (R=0·78). The other taxa of drifting insects showed no significant correlation with the variables measured.Diel (24 h) studies of the major taxa showed marked differences in the periodicity, both within and between taxa, indicating the need for long‐term studies with frequent sample intervals in subtropical habitats. A new drift pattern for the family Chironomidae, alternans type, was observed for late instars of Polypedilum halterale.
Chironomid pupal exuviae in the River Chew
Authors: WILSON R. S. 
Published: May 2006

SUMMARY. Weekly skim‐net samples of chironomid pupal exuviae were collected at a single station on the River Chew, Avon, England, from September 1972 to September 1973. Eighty‐six types of exuviae were characterized in this study, of which sixty‐four made up only 4% of the year's catch. Thirty ‐eight percent of the year's catch was referable to Micropsectra atrofasciata Kieffer.The samples showed the expected maxima of numbers and species in spring and early summer. The emergence periods for many of the more common species were very extended, with one or more peaks.
Habitat and substrate influences on population and production dynamics of a stream caddisfly, Ceraclea ancylus (Leptoceridae)
Authors: RESH VINCENT H. 
Published: May 2006

SUMMARY. Population and production dynamics of Ceraclea ancylus (Vorhies), a leptocerid caddisfly with a univoltine life cycle, five larval instars, and a single cohort population, were examined in Brashears Creek, Kentucky. A systematic sampling approach that included analysis in riffle, pool, and waterwillow bed habitats was used and fourteen sampling transects were taken across Brashears Creek between May 1971 and July 1972. For each of the 70 m2 samples taken along a transect, the depth, habitat, and substrate type were recorded. The number of C. ancylus cases and numbers and dry weights of each larval instar were determined.The majority of the C. ancylus population was in the second larval instar in July, the third larval instar in August, the fourth larval instar in September, and the fifth larval instar from October through May. The spring population was 30% of the early instar maximum estimated the previous August. The spatial distribution of C. ancylus reflects a logarithmic pattern with early instar larvae more highly clumped than the late larval instar and pupal populations. Initial standing stock estimates were less than 1% of the standing stock biomass. A production estimate of 9.9 mg/m2·year (dry weight) was determined using the instantaneous growth method, Allen's Curve method, and the Hynes method of estimating secondary production. Turnover ratios (7.0 annual TR, 5.7 cohort TR) were higher than estimates reported as typical for benthic macroinvertebrates because of the low initial to final mean individual weight of the C. ancylus larvae (0.4%).Production estimates calculated for C. ancylus populations in waterwillow bed (4.4 mg/m2·year) and pool (13.7 mg/m2·year) habitats were less than calculated for the riffle population (19.9 mg/m2·year). The annual turnover ratio (10.2) was higher in the pool population than in other habitats because of spring larval migration into the pool from other habitats. A trend of higher production estimates with larger sized substrate particles and increased numbers of particles may reflect the increase in available food sources or attachment sites. The accuracy of production estimates and their applicability to water resource management may be limited by a failure to consider the spatial distributions of the population being sampled and the tendency for sampling procedures to be confined to single habitats.
Feeding selectivity of a tropical Chaoborus population
Authors: LEWIS WILLIAM M. 
Published: May 2006

SUMMARY. The Chaoborus population of Lake Lanao, Philippines, was sampled weekly over a 65‐week period. Specimens representing all four instars, all times of the year, and two points in the daily migration cycle were dissected for determination of gut contents.Major items in the diet of Lanao Chaoborus include Bosmina, Diaphanosoma, and the copepodid and adult stages of cyclopoid and calanoid copepods. Items that are available but seldom eaten include nauplii and rotifiers except Keratella. Feeding rate averages 2.5% of body weight per day in instars 3–4.Predator size affects but does not fully explain prey selection. Electivity values are much higher for Bosmina and Diaphanosoma than for copepods, even though these food items overlap in size. Bosmina, which has the highest electivity value of any prey, is virtually identical in size to the calanoid nauplius, which has one of the lowest electivity values. This and other similar data suggest that prey of the same size differ greatly in palatability or vulnerability.There is a marked variation in feeding rate and food composition from day to night. The smallest Chaoborus feed more during the day than at night, but the opposite is true for Chaoborus of moderate to large size. Large Chaoborus switch from a daytime emphasis on copepod copepodids and adults to a nighttime emphasis on Cladocera.Diurnal variation between instars in food composition cannot be explained simply on the basis of the vertical distributions of predators and prey. An interaction of vertical distribution with prey density and predator selectivity does explain the overall Chaoborus feeding pattern, however. During the day, larger Chaoborus move deep into the water column where food is scarce. Their daytime feeding rate is lower due to low prey density at great depths. Low prey density is partially compensated by relaxation of preference. At night, upward migration of large Chaoborus into an area of high prey density permits a resumption of marked selectivity and high feeding rates. Small Chaoborus do not descend deep into the water column during the day, as their lower hunting efficiency apparently requires higher food density and use of visual cues to sustain adequate feeding rates. Prey density thus affects both the vertical distribution and feeding selectivity of the Chaoborus population.