Search Results - (Author, Cooperation:J. M. Elliott)

2011-10-25

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Amino Acid Sequence ; Animals ; Cell Line ; Cell Line, Tumor ; Cloning, Molecular ; Humans ; Hydrophobic and Hydrophilic Interactions ; Inhibitor of Apoptosis Proteins/*antagonists & inhibitors/*chemistry/metabolism ; Mice ; Models, Biological ; Models, Molecular ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Proteasome Endopeptidase Complex/metabolism ; Protein Conformation ; Protein Interaction Domains and Motifs ; Protein Multimerization ; Protein Structure, Secondary ; Scattering, Small Angle ; Ubiquitin-Protein Ligases/chemistry/metabolism ; Ubiquitinated Proteins/chemistry/metabolism ; Ubiquitination

2018-02-14

National Academy of Sciences

0027-8424

1091-6490

Biology

Medicine

Natural Sciences in General

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract: Stable transfection of the human neuroblastoma cell line SH-SY5Y with the human 5-hydroxytryptamine2A (5-HT2A) or 5-HT2C receptor cDNA produced cell lines demonstrating ligand affinities that correlated closely with those for the corresponding endogenous receptors in human frontal cortex and choroid plexus, respectively. Stimulation of the recombinant receptors by 5-HT induced phosphoinositide hydrolysis with higher potency but lower efficacy at the 5-HT2C receptor (pEC50 = 7.80 ± 0.06) compared with the 5-HT2A receptor (pEC50 = 7.30 ± 0.08). Activation of the 5-HT2A receptor caused a transient fourfold increase in intracellular Ca2+ concentration. Whole-cell recordings of cells clamped at −50 mV demonstrated a small inward current (2 pA) in response to 10 µM 5-HT for both receptors. There were no differences in potency or efficacy of phosphoinositide hydrolysis among four hallucinogenic [d-lysergic acid diethylamide (LSD), 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane (DOI), 5-methoxy-N,N-dimethyltryptamine, and mescaline] and three nonhallucinogenic drugs (m-chlorophenylpiperazine, quipazine, and ergotamine). Comparison of equipotent doses producing 20% of the maximal response induced by 5-HT revealed selective activation of the 5-HT2A receptor by LSD and to a lesser degree by DOI, mescaline, and ergotamine. Quipazine and 5-methoxy-N,N-dimethyltryptamine were relatively nonselective, whereas m-chlorophenylpiperazine selectively activated the 5-HT2C receptor. It is unlikely therefore that hallucinosis is mediated primarily by activity at the 5-HT2C receptor, whereas activity at the 5-HT2A receptor may represent an important but not unique mechanism associated with hallucinogenic drug action.

Electronic Resource

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract: We have assessed the ability of the serotonergic antagonist mianserin to modulate the number and functional activity of human 5-hydroxytryptamine2A (5-HT2A) and 5-HT2C receptors stably expressed in the human neuroblastoma cell line SH-SY5Y. Incubation of cells expressing the 5-HT2A receptor with mianserin (100 nM) for 24 h caused a significant decrease (48%) in the binding capacity of [3H]ketanserin. This receptor down-regulation was associated with a corresponding decrease in the maximal production of inositol phosphates induced by 5-HT but not by carbachol. Exposure of cells expressing the 5-HT2C receptor to mianserin (100 nM) for 72 h but not for 24 h similarly resulted in a significant reduction (44%) in [3H]mesulergine binding. Corresponding analysis of inositol phosphate production by 5-HT at the 5-HT2C receptor after incubation with mianserin showed no change in maximal response after 24 h. No change in the binding capacity of either radioligand was seen after incubation with mianserin for 1 h. A decrease in the binding affinity of both radioligands was also observed after mianserin treatment, but this decrease was similar after 1 h of incubation to that seen after 24 or 72 h, and was probably due to the retention of mianserin within the tissue. We conclude that antagonist down-regulation is evident at human 5-HT2A and 5-HT2C receptors stably expressed in a human neuroblastoma cell line and is probably mediated by a direct action of mianserin at the receptor.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Brown trout (live weight 9–302 g) were fed to satiation in each of four meals at seven different water temperatures (range 3.8–18.1°C). The period (Ih) from the start of one meal to the start of the following meal was not significantly affected by the weight (Wg) of the trout, but was negatively correlated with water temperature (T°C). A regression equation described the exponential relationship between I and T, and also estimated the number of meals {N) in a day. Values ranged from one meal at about 4°C t o three meals at about 18°C, The greatest increase in appetite occurred at the end of the period I.The maximum weight offood (Drng) eaten in a day was positively correlated with both W and T, a relationship which was well described by a multiple regression equation. The maximum rate of feeding (Fmg h−1) was not significantly affected by W, but increased from 3.8 to 6.8°C, was fairly constant from 6.8 to 19.3°C, and decreased markedly above 19.3°C. Estimates of D and F(with 95% confidence limits) were applicable to a wide variety offood organisms with the exception of mealworms. From comparisons with the results of other workers, it was concluded that the upper limit ofthe daily energy intake determines the optimum temperature for growth.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. 1. The dry weight of food remaining in the stomachs of piscivorous trout decreased exponentially with time. Gastric evacuation rates increased exponentially with increasing temperature but were unaffected by predator size, meal size or type of fish prey.2. Mathematical models were developed to estimate both the rate and time for the gastric evacuation of different meal sizes (expressed as dry weight), and were applicable to piscivorous trout of different sizes (length range 10–32 cm) feeding on trout fry or sticklebacks at different temperatures (range 5–18°C).3. The wet weight of food in the stomachs also decreased exponentially with time, but evacuation rates both increased with temperature and decreased with increasing meal size; the latter relationship occurred because relative rates of water loss from a meal also decreased with increasing meal size. Use of wet or dry weights can therefore lead to different conclusions about the effect of meal size on evacuation rates.4. When piscivorous trout were fed three consecutive meals of varying size, the models predicted the total dry weight of food left in the stomach, but not the weight remaining for each individual meal. Interactions between meals led to an increase in evacuation rates for meals consumed early in the series and a decrease in evacuation rates for later meals.5. Evacuation rates for piscivorous trout were compared with those for trout feeding on invertebrates in an earlier study, and were close to those for caddis larvae as prey, higher than those for mealworms and lower than those for a variety of invertebrate prey. Although a great deal is now known about the daily food intake and growth rates of trout feeding on invertebrates, there is little comparable information for piscivorous trout.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY 1. The objective was to compare variations in egg hatching between the two species (interspecific variations) and between populations of the same species (intraspecific variations). There were significant interspecific, but not intraspecific, differences in female size, adult life-span, egg production, hatching success, incubation periods and hatching periods.2. The optimum temperature for hatching success within the range 3.8–22.1°C in the laboratory and the range over which at least 50% of the eggs hatched were lower for Chloroperia tripunctata (Scopoli) (8.5°C, 4.2–17.3°C) than for Siphonoperla torrentium (Pictet) (12.8°C, 6.1–19.4°C). Few eggs hatched at 22.r°C.3. The relationship between incubation period (d days) and water temperature (T°C) was given by: d=1219/T1.368 for S. torrentium, d=253/T0.459 for C. tripunctata. Both equations successfully predicted incubation periods for eggs placed in a stream. The period over which eggs hatched was much longer for C. tripunctata than for S. torrentium at all temperatures.4. The shorter incubation period (at r〉5.6°C) and shorter hatching period for S. torrentium ensure that larvae of this species are already growing when eggs of C. tripunctata start to hatch, but the prolonged hatching period of the latter species ensures a long period of larval recruitment to the population. These differences in egg hatching may reduce competition between the two closely-related species.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. 1. The chief objective was to determine the major environmental factors affecting the swimming activity of Hirudo medicinalis L. because the latter will affect the feeding and growth periods. 841 leeches were caught in samples taken every 2 weeks in 1982, 1983 and 1984.2. There were four major size groups, probably corresponding to year-classes. Only nine leeches were in their fourth year (Group IV), most leeches found on stones were in their first year (Group I) and most swimming leeches were in their second or third year (Groups II, and III). Size groups I-III overlapped considerably and could not be treated separately in subsequent analyses.3. Water temperature appeared to be the dominant factor affecting swimming activity, the threshold for activity being 7°C (range 5–9°C). A curvilinear regression provided the best description of the relationship between temperature and catches of swimming leeches; 62% (range 50–75%) of the catch variation could be explained by temperature.4. Atmospheric pressure at the time of sampling and its rate of change over 24 h preceding sampling had no significant effect on catches of swimming leeches, not even on the residuals of catches after the dominant effect of temperature had been removed. Similar analyses showed that there were no significant seasonal effects on swimming activity.5. From a discussion of the implications of this study, it is concluded that the absence of the medicinal leech from many water bodies may be due partially to the relatively high temperatures required for swimming activity in a large proportion of the population (11.9°C, 19.0°C, 22.7°C for 10%, 50%, 90% active respectively).

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. 1. Nemurella pictetii Klapæplek took 2 years to complete its life cycle in both the laboratory and a small stream in the English Lake District.2. Hatching time (days after oviposition for 10%. 50% and 90% of the eggs to hatch) and hatching period (days between dates for 10% and 90% hatched) decreased with increasing water temperature in the laboratory, and the relationships were well described by a power-law. Estimates of the mean time for 50% hatching in the stream varied between 16 and 31 days after oviposition. depending on temperature.3. Larval instars numbered fifteen for males and seventeen for females with a constant ratio of 1.18 between successive instars (conformed with Dyar's rule). Larval growth was exponential at four constant temperatures in the laboratory; mean instantaneous growth rates were 0.40±0.01% day−1 at 5.9°C, 0.43±0.01% day−1 at 8.2°C, 0.46±0.01% day−1 at 12. 1°C. 0.56±0.02%day−1 at 19.8°C. No larvae survived after instar XI at 19.8°C.4. Larval growth was exponential in the stream and was scarcely affected by variations in water temperature (range 4.2 -14.0°C); mean growth rates for three year-classes were 0.41±0.02, 0.43±0.08, 0.54±0.05% day−1. Their similarity to laboratory growth rates under optimum conditions suggests that the availability of resources, such as food and space, was not restricting growth in the stream.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

1. Previous studies compared the functional responses to their prey, and both intraspecific and interspecific interference, in mature larvae of Dinocras cephalotes, Perla bipunctata, Isoperla grammatica and Perlodes microcephalus. The present study examines switching by larvae of the same species presented with different proportions of two contrasting prey types; larvae of Baetis rhodani and Chironomus sp. In each experiment, 200 prey were arranged in nine different combinations of the two prey types (20 : 180, 40 : 160, 60 : 140, 80 : 120, 100 : 100, 120 : 80, 140 : 60, 160 : 40, 180 : 20). Prey were replaced as they were eaten. A model predicted the functional response in the absence of switching and provided a null hypothesis against which any tendency for switching could be tested.2. No evidence for prey switching by Dinocras and Perla was obtained, both species showing a slight preference for Baetis over Chironomus. Prey switching occurred in Isoperla and Perlodes. As the relative abundance of one prey type increased in relation to the alternative, the proportion eaten of the former prey changed from less to more than expected from its availability, the relationship being described by an S-shaped curve. Isoperla and Perlodes switched to a preference for Baetis when its percentage of the total available prey exceeded 57 and 42%, respectively. Equivalent values for Chironomus were 43 and 58% for Isoperla and Perlodes, respectively. Switching was strongest in Perlodes.3. Non-switching in Dinocras and Perla was related to their feeding strategy, both species being more successful when using a non-selective ambush strategy at dusk and dawn rather than a search strategy during the night. Both Isoperla and Perlodes used a search strategy. The smaller Isoperla fed chiefly at dusk and dawn, and preferred Chironomus larvae, whereas most of the larger Perlodes fed continuously from dusk to dawn and preferred Baetis larvae.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

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.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. Eggs of Ephemerella ignita (Poda) were kept at eight constant temperatures (range 5.9–19.8°C) in the laboratory. Over 85% of the eggs hatched in the temperature range 10.0–14.2°C but the percentage decreased markedly to 39% at 5.9°C and 42% at 19.8°C. Hatching time (days after oviposition) decreased with increasing water temperature over the range 5.9–14.2°C and the relationship between the two variables was well described by a hyperbola. Therefore, the time taken for development was expressed in units of degree-days above a threshold temperature. Mean values (with 95%CL) were 552 (534–573) degree-days above 4.25°C for 10% of the eggs hatched, 862 (725–1064) degree-days above 3.57°C for 50% hatched and 1383 (1294–1486) degree-days above 3.14°C for 90% hatched. These values can be used to predict hatching times at temperatures below 14.68°C for 10% hatched, 14.54°C for 50% hatched and 14.45°C for 90% hatched. At higher temperatures, the hatching time and the number of degree-days required for development both increased with increasing temperature. Equations were developed to estimate the number of degree-days required for development at these higher temperatures.Eggs were also placed in the Wilfin Beck, a small stony stream in the English Lake District. Maximum and minimum water temperatures were recorded in each week and the summation of degree-days was used to predict the dates on which 10%, 50% and 90% of the eggs should have hatched. There was good agreement between these estimates and the actual hatching times. Only 10–15% of the eggs hatched between October and late February with most of the eggs hatching in March, April and May. Nymphs hatching in October and November probably did not survive the winter.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. The European leech Haementeria costata is recorded in Britain for the first time and is described in detail. A key is provided to distinguish H. costata from other species of leeches in Britain, and the literature on the ecology of H. costata is summarized.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Brown trout of different weights (range 8-358 g) were fed to satiation at fifteen different water temperatures (range 3.8–21.6°C. Both the weight of the trout (Wg) and the water temperature (T°C) affected the maximum weight of food (Q mg) consumed in a meal, and the relationship between the three variables was well described by a multiple regression equation which can be used to estimate the value of Q (with 95% confidence limits) for trout of different weights at different temperatures between 3.8°C and 21.6°C. The satiation time (with 95% confidence limits) can also be estimated from a multiple regression equation for trout of different weights at temperatures between 6.8°C and 18.1°C. Estimates from the multiple regression equations were applicable to a wide range of food organisms with the exception of larvae ofTenebrio molitor (mealworms). Appetite (measured by voluntary food intake) varied with temperature and was greatest between 13.3°C and 18.4°C. From comparisons with the results of other workers, it was concluded that the maximum amount of food consumed in a meal may provide sufficient calories for both the daily metabolic requirements and the daily maintenance requirements of a trout at temperatures between 3.8°C and 18.4°C, but not at temperatures above 18.4°C.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. 1. Brown trout were once given a variety of latin and common names, but are now regarded as belonging to only one polymorphic species, Salmo trutta L. A review of their geographical distribution shows that this species was originally native to Europe but has been successfully introduced in at least twenty-four countries outside Europe.2. Brown trout provide valuable commercial and sports fisheries, e.g. commercial and rod catches of sea-trout in England and Wales averaged 110,547 fish per year from 1983 to 1986 and the minimum value of these fisheries is estimated to be £55M.3. It is concluded from this brief review that the major objectives of scientific research on wild brown trout should be: (a) an assessment of the current status of stocks; (b) the maintenance of existing populations; (c) the development and improvement of mathematical models that can be used as tools for the conservation and management of this important national and international resource.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. After considering the large number of dredges described in the literature, four light-weight dredges were chosen for manual operation from a small boat or the bank: Irish triangular dredge, small Fast dredge, medium-sized and large Naturalist's dredges. The dredges were tested in a series of trials at three sites in two rivers. A stratified random sample (number of sampling units, n = 5) was taken at each site and the modal particle sizes at sites 1–3 were 1–2 mm (fine gravel), 64–128 mm (larger stones) and 128–256 mm, respectively.The dredges usually took a similar range of stone sizes at each site but the design of the Fast dredge excluded larger stones (〉16 mm). The Irish dredge sometimes failed to operate correctly. Variations in the volume of substrata taken with each dredge were large, both between sampling units in the same sample and between samples. The latter differences were partially due to the increase in the modal size of the stones, especially between sites 1 and 2, the different sampling areas of the dredges and the depth of penetration into the substratum. Penetration depth was probably greatest for the two Naturalist's dredges, smaller for the Fast dredge and smallest for the Irish dredge.In field trials, the relative abundances of major taxa were similar for most dredges at each site; major exceptions were the Fast dredge at site 2 and the Irish dredge at site 3. There was a high variability between sampling units in the same sample and therefore a lack of precision in the estimates of the mean number of invertebrates per sample. Therefore, the dredges cannot be used as quantitative samplers for the estimation of population density. Their adequacy as qualitative samplers for the estimation of total number of taxa per sample varied considerably and maximum estimates of their efficiencies for a small sample (n= 5) were 〈40% for the Irish and Fast dredges, 〉57% for the medium-sized Naturalist's dredge and 〉76% for the large Naturalist's dredge.There was a clear relationship between the number of taxa and the number of invertebrates taken at each site and this relationship was well described by a power law with an exponent within the range 0.18–0.53. The number of sampling units in the sample had no significant effect on the power-law equations for each site. The power-law equation was very similar for most of the dredges at each site, the only major exception being the Fast dredge at site 1. The implications of this relationship are discussed.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. After considering the large number of grabs described in the literature, seven grabs of weight 〈 25 kg were chosen for manual operation from a small boat: Van-Veen grab, weighted and unweighted Ponar grabs, Friedinger version of the Petersen grab, Dietz-La Fond mud-snapper, pole-operated Birge-Ekman grab and pole-operated Allan grab.Random samples (number of sampling units n= 10) were taken in a large tank with a known number of 2-mm cylindrical plastic pellets amongst stones of uniform size. Separate experiments were performed with four sizes of stones (model ranges: 2–4 mm, 8–16 mm, 16–32 mm, 32–64 mm). Stratified random samples (n= 10) were taken in rivers and the modal particle sizes at four sites were 0.004–0.06 mm, 0.5–2 mm, 16–64 mm and 64–128 mm. All grabs usually took a representative sample of the substratum at each site with no strong bias towards a particular particle size. The general performance of the Friedinger, Dietz-La Fond and Allan grabs was poor, except on a muddy bottom, with frequent failure to operate, small samples of substratum and a mean depth of penetration 〈 3 cm in all substrata except mud for the Dietz-La Fond and Allan grabs. The Van-Veen and Birge-Ekman grabs sampled to a mean depth 〈 3 cm in mud and fine gravel (2–4 mm), but the Birge-Ekman jammed frequently in fine gravel. Both Ponar grabs operated well and sampled to a mean depth ≥ 5 cm in mud and fine gravel, 〉 3 cm when small stones (8–16 mm) were present and 2 cm (weighted Ponar only) when larger stones (〉 16 mm) were present in a gravel bottom. The mean depth was 〈0.8 cm for all grabs when larger stones (〉16 mm) were predominant on the bottom.In the tank experiments with pellets, the efficiencies for the total catches of the Friedinger, Dietz-La Fond and Allan grabs were low with values 〈45% for fine gravel (2–4 mm), 〈 22% for small stones (8–16 mm) and 〈5% for a substratum of larger stones (〉16 mm). If 50% is the minimum acceptable efficiency, then the Ponar, Van-Veen and Birge-Ekman grabs were adequate for fine gravel, only the two Ponar grabs were adequate for small stones and no grabs were adequate for sampling a substratum of larger stones (〉16 mm).In field trials, the relative abundances of major taxa were similar for most grabs at each site; Friedinger and Dietz-La Fond grabs were the major exceptions. In terms of both mean number of taxa and mean number of invertebrates m−2 the Ponar, Birge-Ekman and Allan grabs performed well on the predominantly muddy substratum at site 1, but only the weighted Ponar grab performed adequately on the predominantly gravel bottom with some large stones (〉16 mm) at site 2. All grabs performed badly when larger stones (〉16 mm) were predominant on the bottom (sites 3, 4).The relationship between the variances and means of the samples taken with each grab followed a power law for the catches of pellets in tank experiments, and for major taxa and total numbers at each site in field trials. Values of exponents in the power law lay within the range 1.14–2.34. The coefficient of variation was also frequently related to the sample mean and was an unreliable statistic for comparing the precision of grabs.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SUMMARY. From 16 air-lift samplers described in the literature, three were selected for operation from a small boat: Mackey, Pearson et al. and Verollet & Tachet samplers. Random samples (number of sampling units n= 10) were taken in a large tank with a known number of dried peas, representing invertebrates, amongst stones of uniform size. Separate experiments were performed with three sizes of stones (modal sizes 2–4, 16–20 and 32–36 mm). Stratified-random samples (usually n= 10) were taken in rivers at lour sites with modal particle sizes of 〈 0.1 2–4. 32–128 and 64–128 mm. The samplers were compared with a Ponar grab in the tank experiments and the field, and with a Naturalist's dredge in the field.Rates of pumping at different air-flows were established for each sampler. Water-How increased with increasing air-How and increasing submergence of the riser-pipe. The Mackey sampler achieved the highest water-flow and lifted more substratum and larger stones (64–128 mm) than the other samplers. The Verollet & Tachet sampler had the lowest pumping rate and failed to lift stones 〉 8 mm long, whilst the Pearson et al. sampler, with an intermediate performance, lifted mud and stones 〈 32 mm long.In the tank experiments, the area from which the Mackey and Pearson et al. samplers collected peas varied with air-flow, operating time and type of substratum. The Maekey sampler over-sampled and the Pearson et al. sampler usually under-sampled their respective sampling areas, except the latter sampler at high air-flows gave approximately quantitative results comparable to those of the Ponar grab for peas on the surface of stones 16–20 mm. No sampler collected much at a depth of 3 cm on larger stones (32–36 mm), and the Verollet & Tachet sampler failed completely on all substrata.In field trials, the Mackey and Pearson et al. samplers provided good qualitative samples except on large stones (32–128mm). The Verollet & Tachet sampler lifted little material. The relative abundance of taxa often differed between samplers. Estimates of the number of invertebrates per m2 differed widely between samplers except for the Pearson et al. and Ponar grab which gave similar quantitative results at three sites. Values were very low for the Verollet & Tachet sampler and Naturalist's dredge and always very high for the Mackey sampler which often grossly over-sampled its sampling area. Therefore, these three samplers cannot be considered as quantitative. The relationship between the variances and the means of samples of peas in the tank and most invertebrates in the field followed a power law with values of the exponent b in the range 1.13–2.51.The present study completes the evaluation of 14 samplers used to sample benthic macro-invertebrates in deep rivers, and the more important conclusions from the comparative studies of seven grabs, four dredges and three air-lift samplers are summarized in a table.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

1. As many invertebrates are nocturnal, their spatial distribution and habitat preferences may change from day to night. Both aspects are examined for Gammarus pulex by testing the hypotheses: (i) a power function was a suitable model for the spatial distribution of the shrimps in both day and night; (ii) diurnal and nocturnal spatial distributions were significantly different; (iii) diurnal and nocturnal habitat preferences were significantly different. Five different life-stages were treated separately. To ensure that the conclusions were consistent, large samples were taken near midday and midnight in April, June and November over 4 years at two sites about 3 km apart in a stony stream: downstream (n = 30) and upstream (n = 50).2. The first and second hypotheses were supported at both sites. A power function, relating spatial variance (s2) to mean (m), was an excellent fit in all analyses (P 〈 0.001, r2 〉 0.91), i.e. the spatial variance was density-dependent. All five life-stages were aggregated in the day. At night, the degree of aggregation increased for juveniles at higher densities but decreased for juveniles at lower densities, increased for immature females and males, but decreased slightly for mature females and especially mature males, the latter being close to a random distribution. There were no significant differences between sites, in spite of the lower numbers at the downstream site.3. The third hypothesis was tested at only the upstream site and supported by comparisons between shrimp densities and 13 physical variables (distance from bank, water depth, water velocity, ten particle size-classes), and three non-physical variables (dry weights of bryophytes, leaf material, organic detritus). During the day, densities were strongly related to particle sizes with the following preferences: 0.5–8 mm for juveniles, 8–256 mm for the other life-stages with a weaker relationship for males. There were no significant positive relationships with the other variables, apart from bryophytes for immature shrimps and adults. At night, densities were unrelated to particle size; juveniles and immature shrimps preferred low water velocities near the banks, often where leaf material and organic detritus accumulated, females often preferred medium water velocities slightly away from the banks, and males showed no habitat preferences.4. Day samples do not provide a complete picture of habitat preferences and probably identify refuge habitats. Day–night changes in spatial distribution and habitat preferences are an essential part of the behavioural dynamics of the shrimps and should be investigated in other species.

Electronic Resource

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

1. Ontogenetic shifts in predator behaviour can affect the assessment of food-web structure and the development of predator–prey models. Therefore, it is important to establish if the functional response and interference interactions differ between life-stages. These hypotheses were tested by (i) comparing the functional response of second, third, fourth and fifth larval instars of Rhyacophila dorsalis, using three stream tanks with one Rhyacophila larva per tank and one of 10 prey densities between 20 and 200 larvae of Chironomus sp.; (ii) using other experiments to assess interference within instars (two to five larvae of the same instar per tank), and between pairs of different instars (one, two or three larvae per instar; total predator densities of two, four or six larvae per tank).2. The first hypothesis was supported. The number of prey eaten by each instar increased with prey density, the relationship being described by a type II model. The curvilinear response was stronger for fourth and fifth instars than for second and third instars. Mean handling time did not change significantly with prey density, and increased with decreasing instar number from 169 s for fifth instars to 200 s for second instars. Attack rate decreased progressively with decreasing instar number. Handling time varied considerably for each predator–prey encounter, but was normally distributed for each predator instar. Variations in attack rate and handling time were related to differences in activity between instars, fourth and fifth instars being more active and aggressive than second and third instars, and having a higher food intake.3. The second hypothesis was partially supported. In the interference experiments between larvae of the same instar or different instars, mean handling time did not change significantly with increasing predator density, and attack rate did not change for second and third instars but decreased curvilinearly for fourth and fifth instars. Interference between some instars could not be studied because insufficient second instars were available at the same time as fourth and fifth instars, and most third instars were eaten by fourth and fifth instars in the experiments. Prey capture always decreased with decreasing attack rate. Therefore, interference reduced prey consumption in fourth and fifth instars, but not in second and third instars. The varying feeding responses of different instars should be taken into account when assessing their role in predator–prey relationships in the field.

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