Radioactive strontium (85Sr) in marking newly hatched pike and success of stocking

Immersion of newly hatched pike fry in an aqueous solution of 1·85 MBq ml⁻¹⁸⁵Sr did not affect their growth or survival over 3 weeks. Cannibal pike fry retained only l.2–3·3% of the ⁸⁵Sr from their labelled prey. Newly hatched ⁸⁵Sr-marked fry stocked into two lakes in 3 years were distinguishable from wild fish 4–6 weeks later. Stocked and wild fry grew equally well, and stocked pike survived best where density of wild pike was highest. There was no evidence of increase in density as a result of Stocking.     

Radioactive strontium (85Sr) in marking whitefish [Coregonus lavaretus (L.)] larvae and the dispersal of larvae from river to sea

Anadromous whitefish [ Coregonus lavaretus (L.)] yolk-sac larvae were marked with a radioactive strontium isotope, ⁸⁵Sr. Before marking the method was tested in accumulation-elimination tests using various strontium concentrations. The first-phase effective half-life of ⁸⁵Sr in yolk-sac larvae was 4 days. The mean ⁸⁵Sr radioactivity was 81 Bq per larva at the day of release and the half-life of the slow component was 51 days, so the strontium label was easily detected up to 60 days after marking. The larvae were released into the River Simojoki about 12 km upstream from the river mouth and recaptured from early May to the end of July. Marked larvae were found at the river mouth 12–13 days after release, while the last marked fish in the river were found at 16 days. It is likely that all leave the river within 2 to 3 weeks post-hatching. Two months after marking some larvae had attained a distance of 10 km from the river mouth.     

微卫星标记分析白斑狗鱼遗传多样性

为了解我国境内白斑狗鱼(Esox lucius)野生群体的遗传多样性现状,利用8对微卫星引物对额尔齐斯河流域185河段、635河段、乌伦古湖及吉力湖4个地理群体的遗传多样性进行了研究。结果显示,8个微卫星位点的平均等位基因数为6.625 0,多态信息含量为0.603 6～0.656 5,可有效用于白斑狗鱼遗传多样性和遗传结构分析。4个群体的平均期望杂合度为0.712 6～0.660 0,表明我国境内野生白斑狗鱼群体有较高的遗传多样性水平。整个群体的总近交系数为0.266 6,少数个体存在近交现象,白斑狗鱼群体有近交倾向。平均分化系数为0.062 2,群体间的遗传变异占总群体变异的6.22%,白斑狗鱼各群体间的分化程度不大。群体间的基因流值变化范围为10.077 5～3.360 6,说明白斑狗鱼不同群体间存在较为广泛的基因交流。     

Chemical alarm signals increase the survival time of fathead minnows (Pimephales promelas) during encounters with northern pike (Esox Lucius)

We tested the hypothesis that exposure to a conspecific alarmpheromone improves survival of fathead minnows (Pimephales promelas)during staged encounters with an unfamiliar predator (northernpike: Esox luaus). Minnows exposed to the alarm pheromone survived39. 5% longer than controls. This difference in survival timeappeared to result not from direct inhibition of the pike butrather from some aspect of the minnows' antipredator behavior.Minnows exhibited significant increases in both shoaling andshelter use after exposure to the alarm pheromone. For controlminnows, the degree of shoaling was positively correlated withsurvival time, suggesting that increased shoaling is an effectiveantipredator response. This study provides the first directexperimental evidence that chemical alarm signals in fishesimprove survival of receivers.     

The effect of arsenic on the thermal tolerance of newly hatched muskellunge fry (Esox masquinongy)

1. 1.The temperature tolerance, Critical Thermal Maxima (CTM), was significantly reduced when newly hatched muskellunge fry were reared in tanks containing 0.05, 1.0 and 5.0 ppm arsenic as sodium arsenite (NaAsO₂).

2. 2.During swim-up (days 8–14 post hatch), CTM decreased from 32.5°C, 30.5°C for fry exposed to 0.05 ppm As. from 32.2°C to 30.°C for fry in 1.0 ppm As and from 31.3°C to 29.3°C for fry in 5.0 ppm. The CTM for the fry exposed to As remained depressed from the onset of swim-up until the experiment was terminated.

3. 3.The control group also displayed a drop in CTM during swim-up from 32.4°C to 30.3°C but the CTM then slowly recovered and increased to 31.8°C on day 15.

4. 4.Swim-up began in all tanks on day 8 and was accompanied by a rapid increase in mortality in those fry exposed to As. 50% mortality was reached 2 days after swim-up began at 5.0 ppm As, 4 days after swim-up began at 1.0 ppm and 5 days after the onset of swim-up for 0.05 ppm. All fish exposed to As died within 7 days after the onset of swim-up.

5. 5.Control fish completed swim-up in 3 days (11 days after hatching), began to feed and appeared normal.

Aluminium interactions with K+(86Rb+) and 45Ca2+ fluxes in three cultivars of sugar beet (Beta vulgaris)

Three cultivars of sugar beet (Beta vulgaris L.), which are sensitive to aluminium (Al) in the order Primahill > Monohill > Regina, were grown in water culture for 2 weeks. Nutrients were supplied at 15% increase of amounts daily, corresponding to the nutrient demand for maximal growth. The 2.4-dinitrophenol (DNP)-sensitive (metabolic) and DNP-insensitive (non-metabolic) uptake of aluminium, phosphate. ⁴⁵Ca²⁺ and K⁺(⁸⁶Rb⁺) in roots were measured as well as transport to shoots of intact plants. All 3 cultivars absorbed more aluminium if DNP was present during the aluminium treatment than in its absence. It is suggested that sugar beets are able to extrude aluminium activity or that they possess an active mechanism to keep Al outside the cell. The presence of Al in the medium during the 1-h experiment affected the metabolic and non-metabolic fluxes of ⁴⁵Ca²⁺ and K⁺(⁸⁶Rb⁺) in different ways. In the presence of DNP, the influx of both ⁴⁵Ca²⁺ and K⁺(⁸⁶Rb⁺) and the efflux of ⁴⁵Ca²⁺ were inhibited by Al in a competitive way. At inhibition of ⁴⁵Ca²⁺ influx, 2 Al ions are probably bound per Ca²⁺ uptake site in cv. Regina (Al-tolerant), but in cvs Primahill and Monohill only one Al ion is bound (more Al sensitive). Aluminium competitively inhibited the active efflux of ⁴⁵Ca²⁺ (absence of DNP) in almost the same way in the 3 cultivars. In contrast, aluminium stimulated the influx of K⁺(⁸⁶Rb⁺) in cvs Primahill, Monohill and Regina in the absence of DNP. Thus, the Al effects on active and passive K⁺(⁸⁶Rb⁺) influx are different. The total influx of K⁺(⁸⁶Rb⁺) increased in the presence of Al and might be connected to an active exclusion of Al. Regina is the least Al-sensitive cultivar, probably because Al interferes less with the Ca²⁺ fluxes and because this cultivar actively excludes phosphate in the presence of Al. Thus Al-phosphate precipitation within the plant could be avoided.     

Studies on the uptake of (14C) amino acids derived from both dietary (14C) protein and dietary (14C) amino acids by rainbow trout, Salmo gairdneri Richardson

Previous studies have shown that rainbow trout fed on diets containing whole protein have superior growth rates compared to fish fed on diets of similar amino acid composition but containing a high proportion of free amino acids. The influence of several nutritional factors on the uptake of radioactivity from food pellets containing either [U-^I4C] protein or [U-¹⁴C] amino acids into the systemic blood of trout has been investigated. The time taken for radioactivity in the free amino acid fraction of blood to reach a peak after a meal containing [U-¹⁴C] protein had been given was much shorter, and the level of radioactivity in the blood higher, in trout with almost empty stomachs than in fish with almost full stomachs; uptake of radioactivity into blood amino acids was also more rapid and reached much higher concentrations when pellets containing [U-¹⁴C] amino acids were fed than when [U-¹⁴C] protein was fed. Incorporation of radioactivity into blood protein continued for a much longer period and reached higher levels when a pellet containing [U-¹⁴C] protein was fed than when a pellet containing [U-¹⁴C] amino acids was fed. Previous dietary history (low or high protein intake) did not appear to affect the rate of absorption of amino acids from either protein or free amino acid pellets. The uptake rates from pellets containing free amino acids could be slowed by mixing the dietary amino acids with albumin. The distribution, postabsorption, of radioactivity in the different fractions of blood and liver suggested that incorporation of carbon residues into glycogen and lipid from an amino acid diet was greater than from a protein diet. The converse was true of incorporation of radioactivity into tissue protein.     

Carbon economy in walnut seedlings during the acquisition of autotrophy studied by long-term labelling with 13CO2

A closed growth chamber was designed to study the acquisition of autotrophy by seedlings of walnut ( Juglans regia L. cv. Lara) in controlled conditions (22°C, 12-h photoperiod) during the first two months of growth. The chamber consisted of two airtight compartments, in which continuous gas exchange was measured on the aerial and subterranean parts of several batches of tree seedlings. Long-term labelling with ¹³CO₂ was used in the chamber to study the import, distribution, and respiratory losses of photoassimilates (autotrophic carbon) in relation to the partitioning and use of reserves of the maternal seed (heterotrophic carbon). The carbon economy of walnut seedlings was estimated by measurements of gas exchange, carbon content, and ¹³C/¹²C isotopic ratio in dry matter and respiratory CO₂. The seedlings were entirely heterotrophic for energy and structural growth during the first 21 days after sowing. From day 22, photosynthesis appeared. At day 29, autotrophic carbon accounted for 25% and 30% of respiration in the root and shoot respectively; these proportions increased to 45% and 65% at day 54. The autotrophic carbon was incorporated into the dry matter of the shoot from day 32 but only after day 40 into the dry matter of the taproot. From day 32, the total contribution of heterotrophic carbon decreased regularly, and until day 43, it was essentially used for root growth. Thereafter, the contribution of heterotrophic carbon was negligible, and at day 54 the walnut seedlings were entirely autotrophic.     

Carbon mobilization in shoot parts and roots of wheat during grain filling: assessment by 13C/12C steady-state labelling, growth analysis and balance sheets of reserves

cv, cultivar
δ, deviation of C isotope composition from a standard
Δ, C isotope discrimination
WSC, water soluble carbohydrates

Steady-state labelling of all post-anthesis photosynthate of wheat was performed to assess the mobilization of pre-anthesis C (C fixed prior to anthesis) in vegetative plant parts during grain filling. Results were compared with estimates obtained by indirect approaches to mobilization of pre-anthesis C: ‘classical’ growth analysis and balance sheets of water soluble carbohydrates (WSC) and protein. Experiments were performed with two spring wheat cultivars grown with differential nitrogen fertilizer supply in 1991 and 1992. The fraction of pre-anthesis C mobilized in above-ground vegetative biomass ranged between 24 and 34% of total C present at anthesis. Treatment effects on mobilization of pre-anthesis C in total above-ground vegetative biomass were closely related (r² = 0·89) to effects on mobilization of WSC-C plus protein-C (estimated as N mobilized × 3·15). On average, 81% of pre-anthesis C mobilization was attributable to the balance of pre-anthesis WSC (48%) and protein (33%) between anthesis and maturity. In roots, WSC and protein mobilization accounted for only 29% of the loss of pre-anthesis C. Notably, mobilization of pre-anthesis C was 1·4–2·6 times larger than the net loss of C from above-ground vegetative biomass between anthesis and maturity. This discrepancy was mainly due to post-anthesis C accumulation in glumes and stem. Post-anthesis C accumulation was related to continued synthesis of structural biomass after anthesis and accounted for a mean 15% of total C contained in above-ground vegetative plant parts at maturity. A close correspondence between net loss of C and mobilization of pre-anthesis C was only apparent in leaf blades and leaf sheaths. Although balance sheets of WSC and protein also underrated the mobilization of pre-anthesis C by ≈ 19%, they gave a much better estimate of pre-anthesis C mobilization than growth analysis.     

Compartmental analysis of efflux of K+(86Rb+) and Rb+(86Rb+) from roots of intact plants of barley (Hordeum vulgare) of high and low K+ status, and after excision of the shoot

The classic compartment analysis of ion efflux from roots is often applied with the assumption that there is a system of 3 compartments in series. However, complex ion transport across the root tissues, as well as influences from the shoot, may complicate the picture. The present experiments were performed to study the immediate effects that excision of the shoot before the experiment exerts on the efflux of Rb⁺(⁸⁶Rb⁺) and of K⁺(⁸⁶Rb⁺) from 9-day-old roots of plants of barley (Hordeum vulgare L. cv. Salve). The efflux from high K⁺ and low K⁺ roots of intact and detopped plants were compared. After excision of the shoot of high K⁺ plants, a marked increase in efflux was observed after 2.5 h with a maximum at about 7 h. The increase in efflux was seen as a peak in plots of efflux versus time. Excision of the shoot from low K⁺ roots did not give rise to a consistent increase in efflux. Regular K⁺ ion efflux curves were observed from roots of intact plants of high or low K⁺ status. Furthermore, after a pulse treatment of 9-day-old roots of intact plants of high or low K⁺ status with a solution containing Rb⁺(⁸⁶Rb⁺), the Rb⁺(⁸⁶Rb⁺) transport to the shoots was not reduced during the following 3 h in unlabelled solution. It is suggested that both the peak appearing in the efflux plots and the maintained tracer transport to the shoots after transfer of the roots to an unlabelled solution indicate the existence of a K⁺/Rb⁺ transport system in the symplasm of the roots that has only a slow exchange with the bulk cytoplasm and vacuoles.     

Nitrate and ammonium influxes in soybean (Glycine max) roots: direct comparison of 13N and 15N tracing

We compared influxes and internal transport in soybean plants (Glycine max cv. Kingsoy) of labelled N from external solutions where either ammonium or nitrate was labelled with the stable isotope¹⁵N and the radioactive isotope¹³N. The objective was to see whether mass spectrometric determinations of tissue ¹⁵N content were sufficiently sensitive to measure influxes accurately over short time periods. Our findings were as follows. (1) There was a close quantitative correspondence between estimates of N influx of individual plants using ¹⁵N or ¹³N measurements with either NO_3/^? or NH₄⁺ at 4 or 2 mol^?3, respectively in the external solution. (2) Transport to the shoot of N from NO₃ absorbed over a 5–15 min period could be monitored when the external NO₃^? concentration ranged from 0–05 to 4 mol m^?3. NH₄⁺ as the N source labelled shoot tissue more slowly, and estimates of the transport between root and shoot could be made only with ¹³N. (3) Influx of NO₃^? into root tissue could be measured by ¹⁵N enrichment after 5–10 min at concentrations approaching the probable K_M of the high-affinity transport system. (4) There was some indication of isotope discrimination, especially with respect to the movement of labelled N to the shoot, when NO₃^? is the N source. For many purposes, ¹⁵N tracing can be used satisfactorily to estimate influxes of both NO₃^? and NH₄⁺ in soybean roots. Use of the short-lived radio nuclide ¹³N remains the method of choice for more refined measurements of internal distribution and assimilation.     

Metabolism of nitrate and ammonium in seedlings of Norway spruce (Picea abies) measured by in vivo 14N and 15N NMR spectroscopy

In vivo ¹⁵N and ¹⁴N nuclear magnetic resonance spectroscopy was used to investigate the assimilation of nitrate and ammonium in seedlings of Norway spruce (Picea abies [L.] Karst.). The main objective was to study accumulation of free NH+₄ and examine to what extent the nitrogen source affects the composition of the free amino acid pools in roots, stems and needles. NH+₄ concentrations in plants growing in the presence of 0.5–50 mM ammonium were quantified using ¹⁴N NMR. The NH+₄ values in tissues ranged from 6 to 46 μmol (g fresh weight)^?1. with highest concentrations in roots and needles. The tissue NH+₄ peaked at 5.0 mM NH+₄ in the medium. and failed to increase when NH+₄ in the medium was increased to 50 mM, indicating metabolic control of the concentration of this cation in tissues. The ¹⁴N NMR spectra were used to estimate pH of the NH+₄ storage pools. Based on the pH sensitivity of the quintet of ¹⁴NH+₄ resonance, we suggest that the pH of the ammonium storage compartments in the roots and stems should be 3.7–3.8, and in needles 3.4–3.5, representing extremely low pH values of the tissue. ¹⁵N from nitrate or ammonium was first incorporated into the amide group of glutamine and then into α-amino groups, confirming that the glutamine synthetase/ glutamate synthase cycle is the major route of nitrogen assimilation into amino acids and thus plays a role in lowering the levels of NH+₄ in the cytoplasm. NH+₄ can also be assimilated in roots in plants growing in darkness. The main ¹⁵N-labelled amino acids were glutamine. arginine and alanine. Almost no ¹⁵N signals from needles were observed. Double labelling (δN + w, wN) of arginine is consistent with the operation of the ornithine cycle, and enrichment indicates that this cycle is a major sink of newly assimilated nitrogen. Nitrogen assimilation in roots in the presence of added methionine sulphoximine and glutamate indicated the catabolic action of glutamate dehydrogenase. The ¹⁵N NMR spectra of plants grown on ¹⁵N-urea showed a marked increase in the labelling of ammonium and glutamine. indicating high urease activity. Amino acids were also quantified using high pressure liquid chromatography. Arginine was found to be an important transport form of nitrogen in the stem.     

Comparison of (R)-[3H] Tomoxetine and (R/S)-[3H] Nisoxetine Binding in Rat Brain

Abstract: ( R )-[³H]Tomoxetine is a radioligand that binds to the norepinephrine (NE) uptake site with high affinity but also binds to a second, lower-affinity site. The goal of the present study was to identify the nature of this low-affinity site by comparing the binding properties of ( R )-[³H]tomoxetine with those of ( R/S )-[³H]nisoxetine, a highly selective ligand for the NE uptake site. In homogenate binding studies, both radioligands bound to the NE uptake site with high affinity, whereas ( R )-[³H]tomoxetine also bound to a second, lower-affinity site. The autoradiographic distribution of binding sites for both radioligands is consistent with the known distribution of NE-containing neurons. However, low levels of ( R )-[³H]-tomoxetine binding were seen in the caudate-putamen, globus pallidus, olfactory tubercle, and zona reticulata of the substantia nigra, where ( R/S )-[³H]nisoxetine binding was almost absent. In homogenates of the caudate-putamen, the NE uptake inhibitors desipramine and ( R )-nisoxetine and the serotonin (5-HT) uptake inhibitor citalopram produced biphasic displacement curves. Autoradiographic studies using 10 n M ( R )-nisoxetine to mask the binding of ( R )-[³H]tomoxetine to the NE uptake site produced autoradiograms that were similar to those produced by [³H]citalopram. Therefore, ( R )-[³H]tomoxetine binds to the NE uptake site with high affinity and the 5-HT uptake site with somewhat lower affinity.     

Passive uptake of K+(86Rb+) in sunflower roots at low external K+ concentrations

Passive fluxes of K⁺ (⁸⁶Rb) into roots of sunflower ( Helianthus annuus L. cv. Uniflorus) were determined at low K⁺ concentration (0.1 and 1.0 mM K⁺) in the ambient solution. Metabolic uptake of K⁺ was inhibited by 10⁻⁴M 2,4-dinitrophenol (DNP). K⁺ (⁸⁶Rb) fluxes were studied both continuously and by time differentiation of uptake. In high K⁺ roots passive uptake was directly proportional to the K⁺ concentration of the uptake solution, indicating free diffusion. This assumption was supported by the fact that passive Rb⁺ uptake was not affected by high K⁺ concentrations. In low K⁺ roots the passive uptake of K⁺ was higher than in high K⁺ roots. The increase was possibly due to carrier-mediated K⁺ transport. As K⁺ effluxes were quantitatively similar to influxes, it is suggested that passive K⁺ fluxes represent exchange diffusion without relation to net K⁺ transport.     

Mechanism for Cd2+ inhibition of (K++ Mg2+)ATPase activity and K+ (86Rb+) uptake join roots of sugar beet (Beta vulgaris)

Steady state kinetics were used to examine the influence of Cd²⁺ both on K⁺ stimulation of a membrane-bound ATPase from sugar beet roots (Beta vulgaris L. cv. Monohill) and on K⁺(⁸⁶Rb⁺) uptake in intact or excised beet roots. The in vitro effect of Cd²⁺ was studied both on a 12000–25000 g root fraction of the (Na⁺+K⁺+Mg²⁺)ATPase and on the ATPase when further purified by an aqueous polymer two-phase system. The observed data can be summarized as follows: 1) Cd²⁺ at high concentrations (>100 μM) inhibits the MgATPase activity in a competitive way, probably by forming a complex with ATP. 2) Cd²⁺ at concentrations <100 μM inhibits the specific K⁺ activation at both high and low affinity sites for K⁺. The inhibition pattern appears to be the same in the two ATPase preparations of different purity. In the presence of the substrate MgATP, and at K⁺ <5 mM, the inhibition by Cd²⁺ with respect to K⁺ is uncompetitive. In the presence of MgATP and K⁺ >10 μM, the inhibition by Cd²⁺ is competitive. 3) At the low concentrations of K⁺, Cd²⁺ also inhibits the 2,4-dinitrophenol(DNP)-sensitive (metabolic) K⁺(⁸⁶Rb⁺) uptake uncompetitively both in excised roots and in roots of intact plants. 4) The DNP-insensitive (non metabolic) K⁺(⁸⁶Rb⁺) uptake is little influenced by Cd²⁺. As Cd²⁺ inhibits the metabolic uptake of K⁺(⁸⁶Rb⁺) and the K⁺ activation of the ATPase in the same way at low concentrations of K⁺, the same binding site is probably involved. Therefore, under field conditions, when the concentration of K⁺ is low, the presence of Cd²⁺ could be disadvantageous.     

Effects of ionic strength and relative humidity on the efflux of K+ (86Rb) and Ca2+ (45Ca) from roots of intact seedlings of cucumber, oat and wheat

Spring wheat (Triticum aestivum L. cv. Svenno), oat (Avena sativa L. cv. Brighton) and glasshouse cucumber (Cucumis sativus L. cv. Bestseller F1) were cultured for a week after germination on complete nutrient solutions of three different dilutions (1, 25 and 50% of the full strength medium). K⁺(⁸⁶Rb) and ⁴⁵Ca were present during the whole culture period. Relative humidity (RH) was 50% except during the last day, when half the material was transferred to 90% RH. Efflux of labelled ions was then followed during eight hours on unlabelled solutions of the same composition as before, and at both 50% and 90% RH in the atmosphere. – Uptake of K⁺(⁸⁶Rb) during growth tended to be saturated in the 25% medium. Contrariwise, the level of Ca²⁺ in the roots increased continuously with strength of the medium. At low concentrations cucumber roots were higher in Ca²⁺ than roots of oat or wheat, whereas all three species showed similar levels of Ca²⁺ in 50% medium. – At the lowest ionic strength, smooth efflux curves were obtained that could be resolved according to the three-compartment theory. At higher ionic strength, irregularities were observed, and more for Ca²⁺ than for K⁺; but for practical purposes compartment analysis with the same time constants could be applied as for the lowest concentration. – Discrimination between K⁺ and Rb⁺ differed between the roots, but not much between the shoots of different species. The roots of oat and wheat took up Rb⁺ preferentially over K⁺ in the 25% and 50% media; whereas K⁺ was preferred over Rb⁺ or little discrimination made in 1% medium and for cucumber. The shoots generally showed less discrimination than the roots. The main variability in discrimination between K⁺ and Rb⁺ thus appears to be localized in the tonoplasts of the roots cells. – Low RH around the shoots increased efflux of K⁺(⁸⁶Rb) from the cytoplasm and vacuoles of the root cells as compared to the efflux at high RH. DNP (2,4-dinitrophenol) in the medium had the same effect as high RH around the shoots. The signal system that must exist between shoots and roots is discussed as a response to “drought” conditions. In relation to investigations of others, it is assumed that the effect of DNP may indicate that part of the chain between roots and shoots consists of metabolically influenced sites, whose output is influenced by the rate of water transport.     

Trophic structure of a boreal forest arthropod community revealed by stable isotope (δ13C, δ15N) analyses

Terrestrial arthropods are important components of boreal ecosystems but relatively little is known about their trophic structure within communities. We measured δ¹³C and δ¹⁵N values in a broad range of arthropod taxa (Coleoptera, Diptera, Ephemeroptera, Homoptera, Hymenoptera, Lepidoptera, Odonata, Orthoptera, Araneae) from boreal forest in Prince Albert National Park, Saskatchewan, Canada. Isotopic measurements supported previous conventional investigations on foraging niches based on stomach content analysis and direct feeding observations but additional, new information was also obtained using the stable isotope approach. Significant differences were observed in both δ¹⁵N and δ¹³C values between various orders and families or superfamilies within orders. Higher variance in stable isotope values for scavengers (e.g. carrion beetles; Coleoptera, Silphidae) and generalists (e.g. ground beetles; Coleoptera, Carabidae) was found compared to specialists (e.g. grasshoppers; Orthoptera). Consistent isotopic differences between terrestrial and aquatic species were not found. However, aquatic insect δ¹³C values tended to be lower than those of their terrestrial counterparts. We discuss the potential for using stable isotope methods to reconstruct trophic linkages and interaction involving arthropods.