Designation of a type species for Brachyptera Newport, 1851 (Plecoptera: Taeniopterygidae)

Nemoura trifasciata Pictet, 1832 is designated as type species of Brachyptera Newport, 1851 (Plecoptera: Taeniopterygidae).     

Life Cycles and Emergence of Ephemeroptera and Plecoptera from Myrkdalsvatn,an Oligotrophic Lake in Western Norway

Comparative data are presented on nymphal growth and adult emergence for Nemoura avicularis, N. cinerea (Plecoptera), Siphlonurus aestivalis, S. lacustris and Leptophlebia vespertina (Ephemeroptera) from lake Myrkdalsvatn, western Norway. These species are all univoltine in Myrkdalsvatn. However, they show different nymphal growth patterns and emergence periods. The timing of emergence in Plecoptera was largely determined by water temperature, and in the Ephemeroptera by changes in both water temperature and cloud cover.     

Diversity of stonefly hexamerins and implication for the evolution of insect storage proteins

Hexamerins are large storage proteins of insects in the 500 kDa range that evolved from the copper-containing hemocyanins. Hexamerins have been found at high concentration in the hemolymph of many insect taxa, but have remained unstudied in relatively basal taxa. To obtain more detailed insight about early hexamerin evolution, we have studied hexamerins in stoneflies (Plecoptera). Stoneflies are also the only insects for which a functional hemocyanin is known to co-occur with hexamerins in the hemolymph. Here, we identified hexamerins in five plecopteran species and obtained partial cDNA sequences from Perla marginata (Perlidae), Nemoura sp. (Nemouridae), Taeniopteryx burksi (Taeniopterygidae), Allocapnia vivipara (Capniidae), and Diamphipnopsis samali (Diamphipnoidae). At least four distinct hexamerins are present in P. marginata. The full-length cDNA of one hexamerin subunit was obtained (PmaHex1) that measures 2475 bp and translates into a native polypeptide of 702 amino acids. Phylogenetic analyses showed that the plecopteran hexamerins are monophyletic and positioned at the base of the insect hexamerin tree, probably diverging about 360 million years ago. Within the Plecoptera, distinct hexamerin types evolved before the divergence of the families. Mapping amino acid compositions onto the phylogenetic tree shows that the accumulation of aromatic amino acids (and thus the evolution of "arylphorins") commenced soon after the hexamerins diverged from hemocyanins, but also indicates that hexamerins with distinct amino acid compositions reflect secondary losses of aromatic amino acids.     

Phenology and Abundance of Ephemeroptera,Plecoptera and Trichoptera Caught by Emergence Traps at the Weidlingbach near Vienna,Austria

A total of 1136 Ephemeroptera, Plecoptera and Trichoptera were caught from March 1993 to March 1994 at the Weidlingbach, a first to fourth order forest brook near Vienna. Austria, using pyramid-type emergence traps at tree sampling stations (390, 360 and 260 m above sea level). Five species comprised 67.1 % of the catch: the ephemeropterans Paraleptophlebia submarginata (Stephens), Habroleptoides confusa Sartori and Jacob and Habrophlebia lauta Eaton, and the plecopterans Nemoura flexuosa Aubert and Leuctra hippopus Kempny. Most taxa emerged from April to August, but the plecopterans Leuctra prima Kempny and Capnia bifrons (Newman) were caught early in the year (January to April), and Leuctra digitata Kempny (Plecoptera), Chaetopteryx fusca Brauer and Chaetopteryx major McLachlan (Trichoptera) emerged in September and October. In Ephemeroptera and Trichoptera, similarities between species groups were highest at the two upstream sampling stations; in Plecoptera and in pooled taxa, however, similarities were highest at the middle and downstream sites. Except in Trichoptera, diversity was highest at the middle station situated at 360 m above sea level.     

Flight Behaviour of Merolimnic Insects from the Leutra River (Thuringia,Germany)

1. The flight behaviour of adult merolimnic insects was studied on the first order limestone stream Leutra (Thuringia, Germany) using sticky traps. The focus of the present study was on testing the colonisation cycle hypothesis of Müller (1954) and on the small-scale dispersal of adult merolimnic insects. 2. A high number of sticky traps was used to guarantee a proper statistical analysis of the data and exclude effects of the heterogeneous environment on flight behaviour. 3. The flight behaviour of Leuctra hippopus, Nemoura cambrica, Nemoura flexuosa, Protonemura nitida, Protonemura praecox (Plecoptera), and Baetis rhodani (Ephemeroptera) was studied. 4. Specific flight corridors were observed for P. praecox, Nemoura spp., L. hippopus and B. rhodani. 5. Comparison of the catches on sticky traps set perpendicular to the water showed no significant flight upstream in any of the taxa studied. Thus, the results do not support the hypothesis of the colonisation cycle.     

Temperature‐Dependent Growth and Life Cycle of Nemoura sichuanensis (Plecoptera: Nemouridae) in a Chinese Mountain Stream

Plecoptera constitute a numerically and ecologically significant component in mountain streams all over the world, but little is known of their life cycles in Asia. The life cycle of Nemoura sichuanensis and its relationship to water temperature was investigated during a 4‐year study in a headwater stream (known as the Jiuchong torrent) of the Xiangxi River in Central China. Size structure histograms suggest that the life cycle was univoltine, and the relationships between the growth of Nemoura sichuanensis, physiological time, and effective accumulated water temperature were described using logistic regressions. The growth pattern was generally similar within year classes but growth rates did vary between year‐classes. Our field data suggest a critical thermal threshold for emergence in Nemoura sichuanensis, that was close to 9 °C. The total number of physiological days required for completing larval development was 250 days. The effective accumulated water temperature was 2500 degree‐days in the field. Development during the life cycle increased somewhat linearly with the physiological time and the effective accumulated water temperature, but some non‐linear relationships were best developed by logistic equations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nymphal trophic behaviour of two Nemouridae species (Insecta,Plecoptera) in the Curone creek (northern Apennines,Italy)

Feeding habits of the Euholognathan stoneflies Nemoura hesperiae and Amphinemura sulcicollis are studied in a little stream located in northern Italy. The former fed mainly on coarse particulate organic matter (CPOM), together with detritus, while the latter fed principally on detritus and, in a lower concern, on CPOM. Thus they can be catalogued fundamentally as shredder and collector‐gatherer, respectively. Shifts in diet composition were detected in relation to size in both taxa. Probably niche overlapping does not exist despite both species having similar size and nymphal development duration, and coinciding in time. This work supports that, though functional feeding groups are very useful, they should not be inferred from related species or higher taxonomical levels. Even intra‐population differences and ontogenetic shifts should be considered in fine scale studies.     

Ecological impact of Eurasian beaver (<Emphasis Type="Italic">Castor fiber</Emphasis>) activity on macroinvertebrate communities in Lithuanian trout streams

Our study found that beaver activity affects macroinvertebrate assemblages of both beaver ponds and downstream sites. The percentage composition of the invertebrate faunae of beaver ponds was strikingly different from the invertebrate faunae of upstream forested and downstream sites. The number of EPT (ephemeropteran, plecopteran, trichopteran) taxa in the upstream forested sites in all streams was higher than in beaver pond and downstream sites. Statistically significant differences were found in absolute and relative abundances of EPT and Chironomidae between different streams sites. The absolute and relative abundance of pollution-sensitive EPT was significantly higher in forested sites than in beaver pond and downstream sites in all measured streams. Beaver ponds had a significantly higher absolute and relative abundance of Chironomidae compared with upstream forested and downstream sites. We found that Plecoptera and Coleoptera were absent from beaver pond sites. The absolute abundance of Plecoptera was significantly higher in upstream forested sites than in downstream sites in all three streams. Gatherers were the dominant functional feeding group in relative abundance in all three habitat types. The percentage of gatherers was higher in beaver ponds than in forested and downstream sites.     

The stoneflies (Plecoptera) of Belarus: Fauna and biotopic distribution

A total of 29 species of stoneflies (Plecoptera) from 7 families were found in Belarus: Perlodidae—6, Perlidae—1, Chloroperlidae—3, Taeniopterygidae—2, Nemouridae—11, Capniidae—2, and Leuctridae—4 species. The fauna is fairly diverse and includes a number of rare species in Belarus and other European countries: Diura bicaudata, Marthamea vitripennis, Isoptena serricornis, Xanthoperla apicalis, Brachyptera risi, Protonemura intricata, Nemoura cambrica, Nemoura marginata, and Capnia bifrons.     

Distribution of benthic invertebrates in acid,brown water streams in the South Island of New Zealand

Acid, brown water streams are common on the west coast of the South Island, New Zealand. Acid precipitation is not a significant problem in this region where stream water acidity is brought about by high concentrations of humic substances. The interrelationships between pH, alkalinity, conductivity, DOC and total reactive aluminium were investigated at 45 running water sites. pH (range 3.5–8.1) was strongly correlated with alkalinity (range 0–49 g·m⁻³ CaCO₃) and less strongly with conductivity (range 2.0–9.7 mS·m⁻¹). A strong positive correlation was found between DOC and total reactive aluminium concentration both of which were correlated negatively with pH. In all brown water streams, most aluminium was probably in the non-toxic, organically complexed form. Benthic invertebrate assemblages were examined at 34 sites. Taxonomic richness was not correlated with pH and similar numbers of ephemeropteran, plecopteran and trichopteran taxa were taken from acidobiontic (pH ⩽ 5.5), acidophilic (pH 5.6–6.9) and moderately alkaline (pH ⩾ 7.0) groups of streams. Many species occurred over a wide pH range and had a lower limit of about pH 4.5. The mayfly, Deleatidium occurred at 33 sites and was amongst the five most abundant taxa at 32 of them. The stoneflies, Zelandobius confusus, Austroperla cyrene and Stenoperla maclellani, an elmid, Hydora sp. and a caddisfly, Psilochorema sp. also occurred in over half the streams and frequently were abundant. Few habitat specialists were found. Benthic assemblages were not associated strongly with measured physicochemical factors but streams in close proximity tended to have similar faunas. This suggests that the availability of suitable colonizers sets the limits to species richness and is important in determining the composition of benthic assemblages at a particular locality.     

The growth of some Ephemeropteran nymphs during winter in a North Swedish River

The growth of the Ephemeroptera species Heptagenia fuscogrisea Retzius, Leptophlebia marginata L. and Ephemerella mucronata Bengtsson was studied from the middle of September 1967 to the middle of May 1968 in the River Rickleån in northern Sweden. Sampling was performed also during periods with ice cover. Growth was estimated from four different body measures and proceeded fairly steady through all the winter for the three species. There were no indications of changed body proportions during the investigation period.     

Emergence patterns of Plecoptera in a stream in Oregon, USA

Forty-three species of Plecoptera were collected from emergence traps in an Oregon woodland stream. Adults occurred during every month of the year, but the largest numbers and most species emerged from April to June. Temporal separation of con-generic species occurred within the suborder of Filipalpia, but not in Setipalpia. Some species of Nemoura had split emergence periods. The onset of emergence for a species from year to year generally varied by less than 2 weeks. Peak emergence occurred at least 1-2 weeks after the start ofthe emergence period.     

Response of macroinvertebrates to blooms of iron-depositing bacteria

In field measurements and laboratory experiments we assessed the influence of high levels of iron, manganese, and concurrent blooms of iron-depositing bacteria, Leptothrix ochracea, on macroinvertebrates. Macroinvertebrate communities in five of six streams were depauerate inside blooms. Reasons for the decreased abundance vary among taxa, with our experiments demonstrating the importance, for one or more species, of (1) direct toxic effects, and,/or smothering, (2) behavioral avoidance of bacterial-coated substrates, and (3) an inability to use bacteria as food. Three mayfly species showed increased mortality when caged inside the blooms, but five trichopterans and one plecopteran did not. Five invertebrates avoided Leptothrix-coated substrate in choice trials, while three did not. Stenonema fuscum could not ingest Leptothrix, and Neophylax nacatus had reduced growth feeding on it, but Heptagenia umbratica grew equally well on diets of Leptothrix or diatoms. This study demonstrates the important role epilithic organisms play in modifying substrates, and how these changes may act to influence benthic abundance and distribution in streams.     

The temperature of two welsh lakes and its effect on the distribution of two freshwater insects

Temperature data are presented from the littoral zones of two lakes in North Wales, Llyn Coron and Llyn Dinas. Recording, mainly on a continuous basis, was over a two year period. Despite their different situations, the lakes had similar temperature regimes. Regional weather factors were of greater importance than local variations. However, some differences were present, especially during the summer months. Laboratory experiments were conducted to determine the temperature relationships of Nemoura avicularis Morton (Plecoptera) and Leptophlebia vespertina (L.) (Ephemeroptera), common species in Llyn Dinas but absent from Llyn Coron. Aspects considered included nymphal temperature tolerance and the effect of temperature on egg development and emergence. From the background of the results, it was concluded that the differences in temperature regime between the two lakes were insufficient to explain the absence of the two species from Llyn Coron.     

Length–weight relationships for some plecoptera and ephemeroptera from a carbonate stream in central Apennine (Italy)

The relationship between dry weight and body length for larvae of Plecoptera (Leuctra spp., Isoperla grammatica, Nemoura cinerea) and Ephemeroptera (Baetis spp., Habrophlebia fusca, Paraleptophlebia submarginata, Ecdyonurus helveticus, Rhithrogena semicolorata), collected from a carbonate stream in the Apennine (central Italy), is reported. The power equation f(x) = Ax ^B has been applied to fit the curves of dry weight vs. body size (length) in the ranges 0.03–13.00 mg and 2–14 mm, respectively; a total of 674 larvae were examined. The power model was in very good agreement with experimental data. Moreover, the error between measured and estimated weight was in the 4–20% range. The data on Isoperla grammatica, Leuctra spp., Rhithrogena semicolorata and Baetis spp. were compared to those in a previous study in a different geographical setting (south-western Germany’s Black Forest) obtaining similar results but with lower errors. We used and compared two methods: the weighted least-square method (WLS) and an analysis of covariance (ANCOVA). The values of the A and B coefficients obtained with the two methods were very similar (<6% discrepancy for either A or B). We found the best fits for all the examined Plecoptera (species, genus, and order level), while the results for Ephemeroptera were varied, with loose fits at the order level and also for Leptophlebiidae collectively considered. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: R. Bailey     

Stream fish assemblages in relation to environmental factors on a montane plateau (Nyika Plateau,Malawi)

Few studies have examined river fishes of Malawi. This study is one of the first to examine the stream fish assemblages on the Nyika Plateau in northern Malawi. Twenty four sites were sampled over three different periods in two river systems of the plateau. Eighteen species were collected and among these was Hippopotamyrus ansorgii, the first collection of this species in the Lake Malawi catchment. Three species, including a non-native trout, were common in the two systems studied. Correspondence analysis (CA) suggested gradients in species composition related to altitude and river type. Species succession, from a trout dominated upstream to a downstream dominated by indigenous species, was shown on the first CA axis. The second CA axis showed the assemblage of the plateau separated by river type. A direct gradient analysis method, canonical correspondence analysis (CCA), showed the importance of two stream position metrics (stream order and c-link), depth, water temperature and substrate type in determining species composition. According to variation partitioning in CCA, the spatial and temporal components respectively explained 46% and 3.6% variation in assemblage composition based on the all species data matrix, and 48.7% and 2.6% variation in assemblage composition based on the native species data matrix. The species collected were also discussed in relation to the morphological adaptations in their body forms to the environmental conditions of the streams studied.     

Assessment of two mesh sizes for interpreting life cycles, standing crop, and percentage composition of stream insects

Using Surber-type samplers and dip-net samplers, we assessed the efficiency of nets having pore sizes of 720 μm and 320 μm for determining standing crop and percentage composition of the stream fauna, and for collecting representative size-class specimens of Ephemeroptera and Plecoptera to be used in life-cycle studies. Except for one species, samples collected with either the 720-μm or 320-μm dip-net led to the same general inferences about the species' life cycle. Of fifty possible sample comparisons, there were twelve samples where the size-class frequencies of particular species collected in the 720-μm dip-net were significantly different from the size-class frequencies of the 320-μm dip-net; for five of these samples a deficit of large nymphs (> 5.0 mm) in the 320-μm net mainly contributed to the significant χ² values. On one date, we used double-bag samplers with both th e 720-μm and 320-μm nets attached to either the Surber or dip-net sampler. Approximately 50% of the insects by numbers passed through the 720 fxm mesh ofeach sampler, but only 5% by volume-biomass. Shape of the insect as well as body length was important in assessing mesh-size efficiencies. The 720-μm mesh of the double-bag dip-net sampler retained most of the Nemoura dnctipes (having stout appendages) and Epeorus longimanus (flattened) nymphs 2.0 mm in body length and larger; whereas most Baetis (streamlined) nymphs smaller than 3.0 mm and all Paraleuctra (needle-like shape) nymphs passed through the 720-μm mesh.     

Forests and the temperature of upland streams in Wales: a modelling exploration of the biological effects

SUMMARY. 1. Daily temperature data from six streams in upland Wales were used to explore the thermal effects of afforestation on stream ecology. The data were linked to published biological models to simulate fish and invertebrate development.
2. Mean daily temperatures in forest streams were lower than those of moorland streams in spring and summer, and higher in winter. These spatial comparisons were supported by the results of experimental bank-side clearance at a forest site, where there was evidence that stream temperatures fell in winter and rose in spring following treatment.
3. Simulations indicated that brown trout (Salmo trutta) could weigh over 30% more by the end of their second growing season in a moorland compared with a forest stream. Several species of insects showed slower simulated egg development at forest sites. For two ephemeropteran species simulated nymphal growth was also retarded, suggesting significant alterations to the life cycle. Two plecopteran species were affected only slightly by the different temperature regimes.
4. Overall, the simulations suggested that afforestation, by reducing summer temperatures, could lead to marked reductions in rates of development of some invertebrates and fish.     

Harpellales (Trichomycetes); mycobionts of insecta

Summary

Species of fungi assigned to the Harpellales, Trichomycetes, occur obligately associated with Insecta. Their possession of monosporous merosporangia (trichospores), zygospores, and crosswalls flared around a plugged central pore augurs for close phyletic affinity with the Kickxellales (Zygomycota). Somatic and reproductive thalli occur attached to the cuticle lining the mid- and hindguts of aquatic dipteran larvae and hindguts of ephemeropteran and plecopteran nymphs. This stage is considered commensalistic. In some species a pathogenic stage of the Harpellales is associated with the ovaries and reduces fecundity. At oviposition fungal spores are deposited by the imago at the sites of new larval populations and provide the primary inoculum.     

Instar sizes,life cycles,and food habits of five Rhyacophila (Trichoptera: Rhyacophilidae) species from the Appalachian Mountains of South Carolina,U.S.A.

The larval head widths at each instar, life cycles, and food habits of late instars were determined for five species of Rhyacophila from two Appalachian mountain streams in South Carolina, U.S.A. Rhyacophila acutiloba Morse & Ross was univoltine with two cohorts, one emerging in the spring and another presumably emerging in early autumn. Rhyacophila fuscula (Walker), R. nigrita Banks, and R. carolina Banks were apparently multicohort, univoltine species with extended flight periods. Rhyacophila minor Banks was univoltine with a spring emergence. All species were predaceous and consumed mainly Plecoptera nymphs and Trichoptera larvae.