Interspecific and intraspecific variations in egg hatching for British populations of Taeniopteryx nebulosa and Brachyptera risi (Plecoptera: Taeniopterygidae)

Adults were obtained from three populations of Taeniopteryx nebulosa and four populations of Brachyptera risi ; their eggs were incubated at seven constant temperatures (range 3.8–22.1°C). There were interspecific, but not intraspecific, differences in adult life-span, mean number of eggs laid per female, hatching success and egg incubation periods. The optimum temperature for hatching success and the range over which at least 50% of the eggs hatched were lower for T. nebulosa (6.5°C, 2.7–15.0°C) than for B. risi (9.0°C, 5.1–15.8°C). No eggs hatched at 22.1°C. The relationship between incubation period (d days) and water temperature (T°C) was given by; d = 326.4 T^−1.015 for T. nebulosa , d = 824.0 T^−0.739 for B. risi . Both equations successfully predicted incubation periods for eggs placed in a stream.
Hatching success and incubation periods were similar to those already published for a Norwegian population of T. nebulosa . The lack of significant intraspecific variation suggests that the genotypes associated with the variables examined in this study have remained remarkably stable in these two species in spite of the geographical isolation of their different populations.     

Inter- and intra-specific differences in the number of larval instars in British populations of 24 species of stoneflies (Plecoptera)

1. Ontogenetic changes during the life cycle of aquatic insects are important not only in life‐history studies but also in evaluating food‐web structure. They require information on the growth and number of larval instars but such information is lacking for many species, including Plecoptera. Therefore, the chief objectives of the present study were to determine inter‐ and intra‐specific differences in the number of larval instars in British populations of 24 species of stoneflies, to test Dyar’s hypothesis that growth followed a geometric progression, and to synthesise this information with previously published values for four British species. 2. Larvae were reared at constant temperatures in the laboratory from eggs from 63 populations (one to six populations per species). First instars from each population were divided into three batches and each batch was reared at one of three constant temperatures. For each species, the rearing temperature and source population had no significant effect on the mean size of each larval instar. 3. The relationship between the geometric mean length of each instar and instar number was well described by an exponential equation (P < 0.001, r² > 0.9 for all species), thus supporting Dyar’s hypothesis. Only one species, Brachyptera risi, had the same number of instars for males and females (12–13). For the other 15 herbivorous species and the four smaller carnivorous ones, the number of instars was higher for females than males (range 11–16 for males, 12–17 for females). The larger size of the females was due to their additional instars, not a sex difference in growth rates. In contrast, there was a clear growth separation of the sexes after the 9th or 10th instar for the four largest carnivores. The number of larval instars was highest for these four species (range 16–19 for males, 18–23 for females), and females were much larger than males. 4. A multiple regression equation with data from the present and previous studies (n = 27) showed that variability in the mean length of the first instar and the maximum number of larval instars for each species accounted for 88% and 91% of the variability in the mean length of the final instar for males and females, respectively. 5. Values for Plecoptera in other countries were in general agreement with those in the present study, especially in the same families. Two old, but widely quoted, high values are doubtful. The present study and four previous ones provide a sound basis for ontogenetic studies on 28 species of Plecoptera and their role in aquatic ecosystems.     

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.     

Post-emergence migration of stoneflies (Plecoptera) into the nearby forest

Abstract. 1. The post-emergence lateral migration of both sexes of eight stonefly species was examined in a dystrophic, fourth-order forest river in eastern Finland.
2. For this purpose, 7351 stonefly adults were collected with eighteen trunk funnels positioned in rows of six at distances of approximately 1, 15 and 60 m from the river. A further 1880 adults were also caught from the vegetation of the bank zone by sweep netting and with slit traps.
3. The species could be grouped into two types with respect to migration distance: Isoperla difformis, I.grammatica and Leuctra fusca tended to stay in the bank area, whereas Nemoura flexuosa, N.avicularis, Amphinemura borealis, L.hippopus and N.cinerea tended to disperse into the forest, so that the majority were found some distance away from the shore.
4. The males of the leuctrids, N.flexuosa and N.cinerea migrated farther than the females.
5. The sex ratio was significantly biased in all species except N.flexuosa. The isoperlids, leuctrids and A.borealis showed a significant predominance of females in the trunk funnel catches, but males were significantly dominant in N.avicularis and N.cinerea. The material caught by other methods reversed the ratio for I.difformis and N.avicularis. Comparison of the sex ratios of the species with other reports revealed marked variation and deviation from unity, much of which could be attributed to bias introduced by the sampling methods.
6. Lateral migration seems to be the first phase in the colonization cycle, although the latter as such was not studied here. Adults of Euholognatha species migrate farther than those of Systellognatha, a difference of which may be due to their ability to feed as adults.     

Egg development of the stoneflies Siphonoperla burmeisteri(Chloroperlidae) and Dinocras cepùnalotes(Perlidae)

SUMMARY. 1. The duration of egg incubation ( Y ) in Dinocras cephalotes and Siphonoperla burmeisteri was related to constant temperatures from 4 to 24°C, by the regression equations Y=2382 T ^{− 1, 402}(r²=0.992, P<0.001) and y= 2683 T ^−1.667 ( r ²=0.994, P <0.001), respectively. No diapause was observed in either species.
2. Egg incubation in D. cephaloles was slow and took 784.9±92.7 (mean ± SD) degree days between 12 and 20°C. significantly more than in S. burmeisteri (445±76.17 degree days: t = 7.44. d.f.=13, P <0.001).
3. For D. cephalotes hatching occurred at temperatures between 12 and 24°C, and for S . burmeisteri between 8 and 20°C. The mean volume of the eggs of D. cephalotes was about 5 times greater than that of S. burmeisteri and the mean body lengths of the newly-hatched nymphs were 1.13 mm and 0.95 mm respectively.
4. This study shows that the freshwater fauna of northern Fennoscan- dia also contains species with warm stenotherm eggs. D. cephalotes. which is of a Mediterranean origin (Zwick, 1981a), may exist at the limit of its distribution in northern Fennoscandia.     

Comparison of ion transportation before and after egg hatching in Amphinemura sp. (Plecoptera)

Abstract.  An increase in egg size with embryonic development in stoneflies is believed to result from the uptake of water by osmosis. The present study aims to investigate whether a selective ion transport through egg membranes exists before hatching, and whether ions are released after hatching. Viable and nonviable egg masses are incubated in Petri dishes filled with water, and the concentrations of the ions F⁻, Cl⁻, SO₄²⁻, NO₃⁻, Na⁺, K⁻, Mg²⁺ and Ca²⁺ in the water are determined. The ion transport of an egg mass before and after hatching and a nonviable egg mass is then calculated. Before hatching, Cl⁻, SO₄²⁻, NO₃⁻, Na⁺, Mg²⁺ and Ca²⁺ are taken up from the surrounding water into the inner egg. These ions are selectively taken into the egg. After hatching, Cl⁻, SO₄²⁻, Na⁺, Mg²⁺ and Ca²⁺ are released into the surrounding water. The amount of these ions released after hatching is lower than the amount taken up before hatching. Ions that are not released after hatching are considered to be used in embryonic development.     

Global diversity of stoneflies (Plecoptera; Insecta) in freshwater

Plecoptera, or stoneflies, is a small order of hemimetabolous insects: according to our data, more than 3,497 species have been described so far in the world. The total number of species has enormously increased in the last 30 years (2,000 species estimated in 1976) and, if the trend continues, then it will nearly double in the near future. The order is divided into the suborders Arctoperlaria and Antarctoperlaria, and includes 16 families: 12 arctoperlarian and 4 antarctoperlarian. The Arctoperlaria account for a total number of 3,179 species, and Antarctoperlaria, only 318 species. The total number of genera is 286. We give in this article the estimated number of species for each family. The fauna and diversity of stonefly in North America (650 species reported) and Europe (426 species) are best known. Nevertheless, in the last 25 years, a mean of 2.6 Plecoptera species per year were described in Europe. Stonefly-faunas of Australia (191 species, Tasmania included) and New Zealand (104 species) are relatively well-known, while our knowledge of the Plecoptera of Central and South America (95 and 378 species respectively) is poor and still not representative of the real diversity. Africa has a reduced stonefly fauna (126 species). Asian stonefly diversity (approximately 1,527 species) is much greater than that of Europe or North America despite the fact that, except for Japan and Asiatic Russia that have been well studied, our knowledge of the remaining Asiatic areas is extremely poor. Even though our data indicate the Holarctic Region as the diversity hot-spot for the order, the analysis of the specific diversity divided by family suggests also an important role of tropical stoneflies. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Implications of imaginal-size variation over the flight period in stoneflies (Plecoptera)

In the present study, the decrease in the mean size of specimens over the species flight period in Plecoptera (12 species, 5 families) was analysed, revealing a significant decrease in the adult mean size, for both males and female, in almost all the species without an extended flight-period pattern. Some of the data show that, in addition to temperature, other regulatory factors must govern these variations. Data support the explanation previously proposed for other insect groups that the individuals with appropriate development emerge at the beginning of the flight period or slightly afterwards, when environmental conditions are suitable, whereas individuals with suboptimal size emerge later trying to increase in size but under pressure to emerge during a specific period of the year. Nevertheless, our data suggest that maximum size does not necessarily coincide with the peak flight period (maximum reproductive possibility).     

DNA barcoding of stoneflies (Plecoptera) in a general genetics course

DNA Barcoding is a powerful molecular biology tool for the identification of species, analysis of gene flow from within and between populations and evaluating species concepts. The process can be incorporated into a college genetics or bioinformatics core curriculum. Here we demonstrate how, by simply using Plecoptera, we actively engaged students in DNA extraction, amplification and DNA Barcoding. As a result, 38 new DNA sequences were accepted by an international DNA database, with potentially three of them being new species to the database. More importantly, through multiple assessment measurements, students showed a high degree of learning took place and that all student learning objectives were met.     

Molecular systematics,evolution and zoogeography of the stonefly genus Siphonoperla (Insecta: Plecoptera,Chloroperlidae)

The stonefly genus Siphonoperla Zwick, 1967 (Chloroperlidae) ranges from the Atlas Mountains of North Africa, throughout Europe and east to the Lesser Caucasus Mountains in Armenia. Systematic relationships within the genus are unknown. We provide the first molecular phylogenetic reconstruction of the genus, based on sequence variation of 1348 bp of the mitochondrial cytochrome c oxidase subunit I gene and relate this phylogeny to a few key morphological features as well as zoogeographical perspectives. A total of 15 taxa (32 individuals), including four outgroup species (Chloroperla Newman, 1836 and Xanthoperla Zwick, 1967 ) were screened. Monophyly of Siphonoperla, as well as each purported taxon was supported, with net pairwise distances ranging from 0.7% to 13.7%. Within‐taxon variability ranged from 0% to 6.2%, whereby the upper value relates to Siphonoperla torrentium Pictet, 1841 represented in our sample by three allopatric subspecific taxa. These taxa, displayed as a polytomy with an estimated time to the most recent common ancestor of about 5.4 Myr, are also shown to have distinct genitalia. These data could be used to support a species‐level distinction for the three subspecific taxa. Siphonoperla ranged from 13% (Xanthoperla) to 16.2% (Chloroperla) divergent from the outgroup genera. The recently described Siphonoperla ottomoogi, Graf, 2008 from Austria is not closely related to the sympatric Siphonoperla montana Pictet, 1841 and is a minimum of 7.8% divergent from congenerics, supporting its status as a micro‐endemic relict surviving on the edge of Alpine glaciation throughout the Pleistocene. Overall, the genus shows the highest levels of diversification in the Mediterranean and Southeast regions whereby at least some of the species found in Central Europe today may have persisted there in peri‐glacial refugia throughout the Pleistocene.     

Biometric studies of some stoneflies and a mayfly (Plecoptera and Ephemeroptera)

Aspects of the nymphal/adult developmental change were investigated in biometric studies of several species of Plecoptera: Nemouridae near Schlitz, Hesse, Germany. Preliminary information on the mayfly, Baetis vernus Curtis, is also provided. Nemourid nymphs pass through 3 wing bearing stages before reaching adulthood. Instars can be identified by their characteristic shapes, as expressed by the wing length/head width (WL/HW) ratio. Size does not allow instar discrimination, mainly due to sexual size differences. HW is ca 10% larger in last instar female than in male nemourid nymphs; exuviae shed at the moult to adult represent about 14% of nymphal ash free dry weight (AFDW). Biomass lost with exuviae during the many larval moults should be accounted for in estimates of production. Freshly emerged nemourid females are about 6% larger and 30% heavier than males. The HW/AFDW relationship is the same in both sexes. Through terrestrial feeding during adult life, males double their weight on average. Mature females are up to three times heavier than freshly emerged ones. They invest about 30% of their final AFDW in reproduction.Shape of last instar nymphal Baetis was expressed as the ratio wing length/mesonotum length. It is size-dependent, a characteristic, instar-specific shape may not occur in this mayfly. Nymphal and subimaginal exuviae together represent about 14% of last instar nymphal dry weight. Females of Baetis are about 55% heavier than males. Unlike in Plecoptera, the size/weight (ML/AFDW) relationship differs between sexes.     

Structure of the ovaries in larvae and mature females of euholognathan stoneflies (Plecoptera)

The morphology of ovaries, oviducts and egg capsules in four species of euholognathan stoneflies was investigated. The characteristic features found were as follows: (i) numerous, long ovarioles, that open individually to the extensively folded, lateral oviducts; (ii) a thin, morphologically undifferentiated chorion; (iii) a thick gelatinous layer (extrachorion) which acts as an adhesive layer fixing the eggs to the substrate. Additionally, in the larval ovariole of Leuctra sp. the terminal filament anlage and clusters of germ cells have been found. These observations are in agreement with the classification of stonefly ovaries as primary (true) panoistic.     

Contribution to the knowledge of the adult feeding of Nemouroidea stoneflies (Insecta: Plecoptera)

The feeding habits of 17 species of Nemouroidea stoneflies (belonging to the families Nemouridae, Leuctridae and Capniidae) from the north‐western Iberian Peninsula are described and quantified by means of gut content analyses. As a whole, fungi, followed by pollen (both from angiosperm and, in a lesser degree, Pinaceae), leaf fragments (CPOM), detritus and, more punctually, lichens and animal matter are the most common items found in their guts. Nevertheless, variations among species were observed. For a species with a flight period that extends throughout the year, Protonemura globosa, variations in the diet were noticed among seasons, with pollen being more important during the spring and summer period. Together with a few previous studies, the present one reaffirms that feeding is an important aspect of the adult life in males and females of Nemouroidea.     

Interspecific and intraspecific variations in sibling species of sea urchin Echinometra

Interspecific and intraspecific morphological and fertilization variations were studied in three sibling species of Echinometra (known as sp. B, C and D) found off the coast of Okinawa, Japan. Eggs from C and D were readily fertilized by sperm from all three color morphs of B when the sperm concentrations were high, but no fertilization was observed when sperm of the former were mixed with eggs from the latter. Under limiting sperm concentrations, however, both C and D were incapable to fertilize reciprocally with B. In contrast, crossing between C and D produced fertilization membrane at high and limiting sperm concentrations in both directions. Interspecific crosses between B vs. C and B vs. D clearly showed that these combinations were reproductively isolated in contrast to that observed for crossing between C and D. Interestingly, intraspecific fertilization of B showed considerable morphological variation in addition to variability in fertilization success. Intraspecific fertilization and morphological variations may occur due to a number of genetic and/or non-genetic factors. While the underlying cause(s) remain to be elucidated, the results of the present study suggest that B is now speciating very slowly.     

A review of stoneflies of the family Taeniopterygidae (Plecoptera) in Russia and adjacent countries

Twenty-one species of the following eight genera of the family Taeniopterygidae were recorded from Russia and adjacent countries (within the limits of the former USSR): Taeniopteryx (4 species), Brachyptera (7), Kyphopteryx (2), Mesyatsia (2), Oempoteryx (1), Rhabdiopteryx (3), Strophopteryx (1), and Taenionema (1). All the species belong to the Palaearctic complex, which is subdivided into the following groups: transpalearctic (1 species), western-Palaearctic (5), Ponto-Caucasian (3: 2 endemics of the Caucasus and 1 species distributed in the Caucasus and Anatolia). Middle-Asian (3), eastern-Palaearctic (1), and Palearchaearctic (1).     

Species loss of stoneflies (Plecoptera) in the Czech Republic during the 20th century

1. Rapid expansion and intensification of anthropogenic activities in the 20th century has caused profound changes in freshwater assemblages. Unfortunately, knowledge of the extent and causes of species loss (SL) is limited due to the lack of reliable historical data. An unusual data set allows us to compare changes in the most sensitive of aquatic insect orders, the Plecoptera, at some 170 locations in the Czech Republic between two time periods, 1955–1960 and 2006–2010. Historical data (1890–1911) on assemblages of six lowland rivers allow us to infer even earlier changes. 2. Regional stonefly diversity decreased in the first half of the 20th century. Streams at lower altitudes lost a substantial number of species, which were never recovered. In the second half of the century, large‐scale anthropogenic pressure caused SL in all habitats, leading to a dissimilarity of contemporary and previous assemblages. The greatest changes were found at sites affected by organic pollution and a mixture of organic pollution and channelisation or impoundment. Colonisation of new habitats was observed in only three of the 80 species evaluated. 3. Species of moderate habitat specialisation and tolerance to organic pollution were most likely to be lost. Those with narrow specialisations in protected habitats were present in both historical and contemporary collections. 4. Contemporary assemblages are the consequence of more than a 100 years of anthropogenic impacts. In particular, streams at lower altitude and draining intensively exploited landscapes host a mere fragment of the original species complement. Most stonefly species are less frequently present than before, although their assemblages remain almost intact in near‐natural mountain streams. Our analyses demonstrate dramatic restriction of species ranges and, in some cases, apparent changes in altitudinal preference throughout the area.     

Molecular phylogeographic analysis of East Asian cryptoperlan stoneflies (Insecta: Plecoptera, Peltoperlidae)

Cryptoperlan stoneflies inhabit the headwaters or upper stream areas of rivers. A molecular phylogeographic study of cryptoperlans in the Japanese archipelago and on Taiwan Island has been conducted. Altogether the mtDNA 16S rRNA region of 71 individuals from 61 populations, the mtDNA COI region of 76 individuals from 41 populations, and the nDNA Histone 3 region of 56 individuals from 52 populations were sequenced and analyzed. The respective ML, NJ, MP and Bayesian dendrograms were proposed from the sequencing data for the 16S rRNA region (362-bp), the COI region (540-bp), and the Histone 3 region (322-bp), estimated using Yoraperla uenoi as an outgroup. Based upon those data and the resulting dendrograms, it has become clear that the cryptoperlan stoneflies of the Japanese archipelago and those of Taiwan Island comprise two major clades. The first of these two major clades consists of a number of OTUs [operational taxonomic units: Cryptoperla japonica (Honshu, Shikoku and Kyushu Islands) + C. ishigakiensis (Ishigaki-jima Island) + Cryptoperla spp. (Okinawa-jima and Taiwan Islands)]. The other clade consists of the species Cryptoperla kawasawai inhabiting only Shikoku Island. Of particular note, C. kawasawai was observed to be significantly genetically differentiated from all other cryptoperlans examined. Yet, despite the fact that the specimens of C. japonica were taken from a very broad range of populations, their genetic diversity was relatively low, similar to that of C. kawasawai, which inhabits only a limited region within Shikoku Island. Furthermore, even the species C. kawasawai was revealed to be composed of two significantly genetically differentiated subclades. It is considered that this genetic structure among cryptoperlans largely reflects the geological history from the middle to upper Miocene Epoch (i.e., Tortonian stage) of the Japanese archipelago and Taiwan Island.     

Diet and predation by three leaf-associated stoneflies (Plecoptera) in an Arkansas mountain stream

SUMMARY. 1. Life cycles, food habits, mouthpart morphologies, prey preferences, and predator-prey size relationships were investigated for the three most common stoneflies in leaf packs in the Little Missouri River, Arkansas: Clioperla clio (Newman), Isoperla namata Prison, and Perlesta spp. Each species was univoltine and had a fast seasonal cycle, with extended egg or nymphal diapause, rapid nymphal growth and emergence in spring to early summer.
2. Foregut analysis showed predictable dietary shifts by C. clio and Perlesta spp., from detritus and diatoms in early instars to invertebrate prey in later instars. Isoperla namata fed facultatively on insects, detritus and diatoms, with no conspicuous ontogenetic shifts. The mouthparts of all three species strongly reflected their diet.
3. Electivity analysis indicated opportunistic feeding by the three species, with feeding rarely differing significantly from random.
4. Sizes of stonefly predators and their ingested prey were highly correlated ( P <0.01). However, rather than shifting toward larger prey sizes, growing predators expanded their size thresholds and continued to include numerous small prey items in their diet. Prey choice was governed most directly by prey availability, because stoneflies selected the most abundant groups, irrespective of size or taxon.
5. The likelihood of competition among the three stoneflies for prey was minimized by timing of their life cycles, differential food use and probably the temporary nature of leaf pack habitats.     

New stoneflies (Insecta: Perlida = Plecoptera) from Eocene Rovno amber,Ukraine

A new genus, Rovnocapnia gen. nov., with new species R. atra sp. nov. and R. ambita sp. nov., from the family Capniidae, and a new genus and species Palaeoleuctra acuta gen. sp. nov., from the family Leuctridae, of the suborder Nemourina (Euholognatha), are described from Late Eocene Rovno amber. Familial assignment of one additional specimen (suborder Perlina, infraorder Perlomorpha (Systelognatha)), represented by a nymphal skin, is obscure due to its incomplete preservation.