We present a genome assembly from an individual male
(black needle fly; Arthropoda; Insecta; Plecoptera; Leuctridae). The genome sequence is 536.3 megabases in span. Most of the assembly is ...scaffolded into 13 chromosomal pseudomolecules
including the X sex chromosome. The mitochondrial genome has also been assembled and is 17.6 kilobases in length.
The biotic resistance hypothesis provides one of several explanations for the limited biological recovery of streams recovering chemically from acidification. The hypothesis proposes that ...acidification has changed the presence, abundance and interactions among species in acidified streams to the extent that acid-sensitive colonists cannot re-invade even where acidity has ameliorated. As a first step in testing for biotic resistance in streams, we conducted a field experiment to determine whether the success (growth rate) of acid-sensitive recolonists (mayfly nymphs, Baetis rhodani) is reduced by competition with abundant acid-tolerant residents (stonefly nymphs, Leuctra inermis) in a chemically recovering Welsh stream (UK). Gut contents analysis revealed a marked overlap in resource use between the two species. However, when Baetis was exposed to several (0, 0.25, 0.5 and 1 times ambient) densities of its putative competitor, Leuctra, growth rates of the colonist were not affected by the residents at any of the densities tested. These results do not support the hypothesis that resident species constrain colonist populations by affecting growth rates through competition for limited resources or interference. Further work is required to assess whether independent and/or interactive ecological effects of other common residents might affect colonists in ecosystems recovering from past stressors.
The compilation of a DNA barcoding library of Norwegian stonefly (Plecoptera) species revealed that Leuctra fusca (Linnaeus,
1758
) and Leuctra digitata Kempny, 1899 (Leuctridae) share haplotypes in ...northernmost Scandinavia. Phylogenetic analyses of the mitochondrial (mt) DNA barcode marker COI and the nuclear marker 28S show that the shared haplotypes must result from the introgression of a L. fusca mitochondrion into a L. digitata population on at least two occasions. Although mt introgression is widespread in animals, this represents the first documented case in Plecoptera. This study also included specimens of L. cf. fusca from the Sierra Nevada massif in Spain, a population previously known as L. carpentieri Despax, 1945. Their mt haplotypes are ca. 13% different from other European L. fusca. However, their 28S alleles are compatible with their morphological identification as L. fusca. In view of the possibility of mt introgression, the taxonomic status of this population remains undecided.
1. We analysed a large number of concurrent samples of macroinvertebrate communities and chemical indicators of eutrophication and organic pollution total-P, total-N, NH₄-N, biological oxygen demand ...(BOD₅) from 594 Danish stream sites. Samples were taken over an 11-year time span as part of the Danish monitoring programme on the aquatic environment. Macroinvertebrate communities were sampled in spring using a standardised kick-sampling procedure whereas chemical variables were sampled six to 24 times per year per site. Habitat variables were assessed once when macroinvertebrates were sampled. 2. The plecopteran Leuctra showed a significant negative exponential relationship (r² = 0.90) with BOD₅ and occurred at only 16% of the sites with BOD₅ above 1.6 mg L⁻¹. Sharp declines with increasing BOD₅ levels were found for the trichopteran families Sericostomatidae and Glossosomatidae although they appeared to be slightly less sensitive than Leuctra. Other plecopterans such as Isoperla showed a similar type of response curve to Leuctra (negative exponential) but occurred at sites with relatively high concentrations of BOD₅ up to 3-4 mg L⁻¹. In contrast, the response curve of the isopod Asellus aquaticus followed a saturation function reaching a plateau above 3-4 mg L⁻¹ BOD₅ and the dipteran Chironomus showed an exponential increase in occurrence with increasing BOD₅ concentration. 3. Macroinvertebrate occurrence appeared to be related primarily to concentrations of BOD₅, NH₄-N and total-P whereas there were almost no relationships to total-N. Occurrence of a number of taxa showed a stronger relationship to habitat conditions (width and substrate) than chemical variables. 4. Important macroinvertebrate taxa are reduced at concentrations of BOD₅ that are normally perceived as indicating unimpacted stream site conditions. Our results confirmed sensitivity/tolerance patterns used by existing bioassessment systems only to some degree.
•Lambda-cyhalothrin overrules anti-predator behaviour of Gammarus pulex during exposure.•Lambda-cyhalothrin overrules predator behaviour of G. pulex during exposure.•Sublethal lambda-cyhalothrin ...concentrations may have cascading effects.
In this study, we aimed to evaluate the effects of a short pulse exposure of the pyrethroid lambda-cyhalothrin (LC) on the predator and anti-predator behaviour of the same species; Gammarus pulex. Predator behaviour, at the level of the individual, was studied in indoor microcosms using video tracking equipment during simultaneous exposure of the predator (G. pulex) and its prey (Leuctra nigra) during 90min exposure of 1, 6.6 or 62.1ngL−1 LC. During an initial 30min of exposure, the predator and prey organisms were maintained physically separated, and the actual interaction was studied through the subsequent 60min of exposure. The anti-predator behaviour of G. pulex (drift suppression in response to the presence of brown trout) was studied in outdoor stream channels during a 90min pulse exposure to LC (7.4 or 79.5ngL−1) with, or without, brown trout. Based on survival curves for L. nigra we found that the mortality rate for L. nigra significantly decreased during exposure to 6.6 and 62.1ngL−1 LC (P<0.05 and P<0.001, respectively). We found no significant effects suggesting that G. pulex was repelled by contaminated prey items (P>0.05). We found that the exposure of G. pulex to 7.4 and 79.5ngL−1 LC significantly increased drift (from ∼0% to ∼100% in both treatments; P<0.001) independent of the presence of brown trout (P<0.05). In other words, the natural anti-predator behaviour of G. pulex was overruled by the stress response to LC exposure increasing G. pulex predation risk from drift feeding brown trouts. Our results show that the anti-predator and predator behaviour of G. pulex were significantly changed during exposure to very low and environmentally realistic LC concentrations and exposure duration. The potential implications for the field scenario are discussed.
We studied the nymphal biology (life cycle, secondary production and feeding) of some Plecoptera species in a calcareous spring stream with almost constant temperature through the year (7–8°C) at ...Prosiek valley (Chočské Vrchy Mts., West Carpathians, Slovakia). We found complicate life cycle consisting of two cohorts for Leuctra prima with growth rate positively correlated to photoperiod length. Isoperla sudetica showed an univoltine life cycle. The annual secondary production of the stonefly community was reaching 4304mgDWm−2. It was mainly related to the abundance of three dominant species –I. sudetica, L. prima and Protonemura intricata – and to the permanence of their nymphs in the water through the whole year. We suppose that the stable thermal regime is a factor which could allow high production and biomass values, irrespective of seasons. Nymphs of I. sudetica passed from gatherer-collector to predator and nymphs of L. armata passed from gatherer-collector to shredder during their development.
Both molecular and morphologic characters support the reinstatement of
Leuctrabiellensis
Festa, 1942 as a valid species distinct from
Leuctranigra
(Olivier, 1811). Genetic distances between
...L.biellensis
and the different populations of
L.nigra
are around 9%, while intraspecific distances among
L.nigra
haploclades are less than 1%. Morphologically, the two species can be separated in male adult specimens by the shape of the two teeth on tergite VIII, by the lateral edges of tergites and by the distal expansion of the paraprocts.
Leuctrabiellensis
occurs on the southern slope of the Alps in Italy and Switzerland (Ticino and Graubünden), while
L.nigra
has a wide distribution in Central and Northern Europe. As the type material of
L.biellensis
was lost, and to avoid future confusion between the two species, we designate as neotype a male imago collected at the type locality.
1. The delivery, entrainment and deposition of inert fine sediments are among the most significant contributors to stream and river impairment worldwide. Associated ecological effects have been ...observed frequently, but specific experiments to identify sensitivity and avoidance behaviour in stream organisms are few, particularly in headwaters. 2. In a field-experiment, we added fine sand at low levels (c. 4-5 kg m⁻²) to 10 m reaches of two replicate headwater streams in the Usk catchment (Wales, U.K.) over two periods (autumn and summer). Upstream reaches were used as control in a classic before-after-control-impact design. Invertebrate drift and benthic composition were measured for 2 days before and 1 day after sediment impact. 3. Sediment addition significantly increased overall drift density (by 45%) and propensity (by 200%), with effects largest on the night following addition rather than immediately (i.e. within 9 h). The mayflies Baetis rhodani, B. muticus and Ecdyonurus spp., simuliid and chironomid dipterans, and helodid beetles were the strongest contributors. 4. There were no marked effects on benthic composition, but density declined in treated reaches by 30-60%, particularly in B. rhodani, Ecdyonurus spp. and Leuctra hippopus + L. moselyi. 5. All effects were consistent between both seasons and streams. 6. These data show how even low-level, short-term, increases in fine sediment loading to upland, stony streams can reduce overall benthic density through increased drift. We suggest that the likely cause of the delayed drift response was a change in habitat quality which prompted avoidance behaviour. Longer-term experiments are required to assess whether these effects reduce fitness or explain the losses of some types of organisms observed recently in sediment-impaired reaches of this and other catchments.
1. Emergence and inland dispersal of adult stoneflies (Plecoptera) and caddisflies (Trichoptera) from Broadstone Stream, an acidic and iron‐rich stream in southern England, were studied over 10 ...months in 1996–1997. Fifteen pyramidal emergence traps were placed randomly in a 200‐m stretch. Three Malaise traps were placed above the stream and six more on each side (one wooded, one open) along a transect at distances of 1, 15, 30, 45, 60 and 75 m from the channel.
2. More than 16 000 stoneflies, belonging to 11 species, and just under 400 caddisflies (22 species) were caught. Four dominant stoneflies (Leuctra fusca, Leuctra nigra, Leuctra hippopus and Nemurella pictetii) accounted for 96% and 95% of the catches in the emergence and Malaise traps, respectively. Two caddisflies (Plectrocnemia conspersa and Potamophylax cingulatus) accounted for 63% of the catch in the Malaise traps. Few caddisflies were taken in emergence traps.
3. The emergence periods of L. fusca, L. nigra and L. hippopus were well‐defined and unimodal, whereas that of N. pictetii was prolonged and erratic. Overall, more females (1285) emerged than males (740).
4. Female stoneflies and caddisflies were in the majority in the Malaise traps above the stream. On land, significantly more females than males of L. fusca, L. nigra and P. cingulatus were caught. The sex ratio of the remaining species did not deviate significantly from 1:1.
5. The three Malaise traps placed above the stream caught most of the stoneflies though there was also dispersal away from the channel, the numbers caught declining with distance. Exponential models explained between 67% and 99% of the variation in numbers of individuals with distance from the channel in the four common stoneflies. Half the individuals went less than 11–16 m from the stream, while 90% travelled less than 51 m. Significantly more L. nigra and N. pictetii were caught in the woodland than on the open side, whereas L. hippopus showed no overall preference for either side.
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