Sexual dimorphism and the influence of artificial elevated temperatures on body size in the imago of Nemoura trispinosa (Plecoptera: Nemouridae)

Our study site was composed of a spring that was divided lengthwise from its source into two equally wide channels, with water temperature in the experimental channel being increased by 2.0–3.5°C relative to that of the control channel. We examined sexual dimorphism in overall body size and eight morphological traits in the stonefly Nemoura trispinosa Claassen, and whether body size varies according to site of emergence (upstream versus downstream) and/or the thermal regime in which they undergo nymphal development. Univariate tests showed that females were significantly larger than males in all eight traits, and multivariate analyses (Principal Components Analysis) demonstrated that females were larger in overall body size. Both univariate and multivariate tests showed that adults emerging from the control and downstream portions of the stream were larger than those from heated and upstream reaches, respectively. We discuss possible hypotheses contributing to the female-biased sexual dimorphism observed in this species.     

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)     

Oocytes develop from interconnected cystocytes in the panoistic ovary of Nemoura sp. (Pictet) (Plecoptera : Nemouridae)

The 2 ovaries of Nemoura sp. (Plecoptera : Nemouridae) are comb-like and house about 60–70 ovarioles each. By ultrathin serial sections through a whole ovariole of a last-larval instar, we gathered information on its ultrastructure and 3-dimensional architecture. The germarial region contains several clusters of interconnected oogonia or oocytes. The intercellular bridges (ring canals) are filled with fusomes. Most of the fusomes assemble to polyfusomes and some of the intercellular bridges move together and their cells assemble to rosettes. Results indicate that existence of polyfusomes is not sufficient for rosette formation. The oogonia or oocytes of each cluster develop synchronously. Oocytes detach from clusters next to intercellular bridges. A transdetermination of oogonia to nurse cells does not occur. Thus, the stone flies remain true panoists.     

Life histories of Nemouridae and Leuctridae in Southern Ontario (Plecoptera)

The life-histories of seven species of Nemouridae and two of Leuctridae have been investigated in Southern Ontario. Eleven sampling stations were chosen to illustrate the range of temperature conditions found in local streams.The Nemouridae and Leuctridae make up most of the stonefly fauna of the upstream cooler stations, but their numerical importance decreases considerably downstream.There is a definite seasonal succession of the species: Soyedina aallicularia, Prostoia completa and Shipsa rotunda appear in late spring, Nemoura trispinosa, Amphinemura delosa} and A. nigritta in early summer, Leuctra tenuis in midsummer and A. linda in late summer. L. ferruginea emerges throughout most of the summer, at least in the headwater streams.All the species are univoltine, except L. ferruginea which is usually semivoltine. Most Nemouridae, A. spp., P. completa and S. rotunda undergo a long embryonic diapause, whereas N. trispinosa and S. vallicularia develop directly. The nymphal development of N. trispinosa was compared in three streams; although the general pattern is similar, the growth is much more synchronized in the warmest station. There appears to be 16 nymphal instars in this species. L. ferruginea was common in seven stations; in the coolest, the life-cycle lasts two years, but in the warmest, many specimens succeed in completing their cycle in one year.

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Résumé Les cycles vitaux de sept espèces de Nemouridae et deux espèces de Leuctridae ont été étudiés dans onze ruisseaux du Sud de l'Ontario; ces stations d'échantillonnage représentent la gamme des températures des ruisseaux de cette région.Les Nemouridae et les Leuctridae constituent la majeure partie de la faune des Plécoptères dans les stations froides de l'amont. Cependant, leur importance décroît de façon significative dans les stations plus en aval.On reconnaît une succession bien définie des espèces durant l'année: Soyedina aallicularia, Prostoia completa et Shipsa rotunda apparaissent à la fin du printemps, Nemoura trispinosa, Amphinemura delosa et A. nigritta au début de l'été, Leuctra tenuis au milieu de l'ete et A. linda à la fin de l'été. L. ferruginea emerge pendant presque toute la saison chaude, du moins dans les stations de l'amont.Toutes ces espèces sont univoltines, sauf L. ferruginea qui est ordinairement semivoltine. La plupart des Nemouridae, soient A. spp., P. completa et S. rotunda doivent compléter une longue diapause embryonnaire, alors que N. trispinosa et S. vallicularia se développent directement. On a comparé la vie larvaire de N. trispinosa dans trois ruisseaux: bien que l'essentiel de la biologie soit semblable dans les trois cas, on remarque un plus grand synchronisme de la croissance dans la station la plus en aval. Il semble y avoir 16 stades larvaires chez cette espèce. L. ferruginea était abondante dans sept stations; dans la plus froide, le cycle vital dure deux ans, alors que dans la plus chaude, plusieurs specimens arrivent a boucler leur cycle en un an.

     

The Group of Amphinemura flavostigma (Plecoptera,Nemouridae)

Three closely related species from Japan are treated and defined as composing the Amphinemura flavostigma group (Okamoto, 1922). One species, A. nikkoensis, is described as new to science. Two already known species, A. flavostigma and A. monotuberculata (Kawai, 1956), are redescribed, while the female of the latter is described for the first time. Another species, A. tetraspinosa Kawai, 1960, is regarded as a subjective synonym of Nemoura flavostigma Okamoto, 1922.     

The biology and life cycle of Nemoura avicularis Morton (Plecoptera)

Data are presented on the biology and life cycle of Nemoura avicularis Morton in a North Wales lake, Llyn Dinas, and in the laboratory. Aspects of egg, nymphal and adult biology are described and discussed. Special attention is given to the early instars. The life cycle in the field was followed for a 2-year period. Eggs hatched during April, May and the first half of June, and growth then continued more or less continuously until late January when the nymphs were fully grown. Emergence, however, did not begin until March, reaching a peak in April and continuing into the early part of May. In the laboratory N avicularis was reared through its life cycle from egg to adult. The results of the present study are discussed in relation to previous research on the biology and life cycle of N. avicularis.     

Food preference, growth and maturation of Nemurella pictetii (Plecoptera: Nemouridae)

1. The stonefly Nemurella pictetii has a highly variable life cycle and is semi‐ and uni‐, but also plurivoltine in different geographical areas. 2. The influence of the type of food on growth and maturation of larvae was studied in laboratory experiments. Food preference was also assessed. 3. Larvae of N. pictetii are strongly opportunistic feeders utilising a broad range of food sources. However, biofilm was preferred over detritus (conditioned leaves), green algae and animal food. The highly mobile larvae quickly found the preferred food. Larvae fed on biofilm grew and developed significantly faster than larvae fed on conditioned leaves. 4. Larval growth and maturation in experiments as well as in the field differed with available food qualities. Phases of faster growth and maturation corresponded well with maximum availability of biofilm in the field. This contributes to the interpretations of differences in life cycles in the field.     

Life history and parasites of the invasive mosquitofish (Gambusia holbrooki) along a latitudinal gradient

The eastern mosquitofish (Gambusia holbrooki) is among the most invasive fish worldwide and yet, while very abundant in most Mediterranean countries, it is unable to tolerate the colder winters of northern and central Europe. Understanding the effects of latitude on its life-history traits is essential to predict the potential for its invasion of central Europe in current scenarios of climate change. We studied the variation of life-history traits and parasite load in the eastern mosquitofish along a latitudinal gradient from southern France to southern Spain, sampling mosquitofish populations in eight Mediterranean river mouths ranging 5° in latitude. Southern mosquitofish populations displayed higher catch rates, allocated more energy to reproduction (gonadosomatic index and gonadal weight after accounting for fish size) and had a lower condition (total weight and eviscerated weight after accounting for fish size) than in northern populations. Despite variability among populations, size-at-maturity (L₅₀) significantly varied with latitude and northern individuals matured at smaller size (lower L₅₀). Parasite prevalence ranged from 0.0 to 26.7% but parasite richness was very low; all the parasites identified were larvae of pleurocercoid cestodes belonging to the order Pseudophyllidea. The abundance of mosquitofish parasites decreased with latitude and the presence and number of parasites infecting the mosquitofish had a significant negative effect on fish condition. The significant effects of latitude on the catch rates, life history and parasites of mosquitofish highlight the importance of latitudinal studies of invasive species to understand the interactive mechanisms of climate change and biological invasions.     

新疆倍叉(虫责)属一新种记述(襀翅目:叉(虫责)科)

本文记述了采自新疆喀纳斯的倍叉[虫责]属Amphinemura 1新种：环齿倍叉[虫责]Amphinemura tricintusidens Wang＆Zhu,sp．nov。根据肛侧突中叶端部有3或4个环绕的小齿和肛上突背骨片端部形成的圆形腔可将该新种与其它种类相区别。正模♂,新疆喀纳斯,2005-Ⅷ—01,朱江艳等采。副模1♂,采集资料同正模。新种的模式标本保存在扬州大学昆虫标本馆。     

Plurimodal emergence and plurivoltinism of Central European populations of Nemurella pictetii (Plecoptera: Nemouridae)

Summary Nemurella pictetii Klapálek, 1900 (Plecoptera: Nemouridae) has bi-or trimodal emergence patterns in Central Europe. The emergence threshold temperature is about 8°C. Egg development is direct. The slopes of regressions describing its temperature dependence do not differ significantly between English, Norwegian and German populations, but the intercepts (i.e., the incubation period at 0°C) do. Regular sampling of a benthic population near Schlitz, in Hesse, West Germany, showed that part of the offspring of the first emergence group grew quickly and produced a second emergence peak. The remaining offspring of the first generation grew more slowly and overwintered, together with the offspring of the second emergence peak. This population exhibits partial bivoltinism. The potential for bivoltinism was also shown in laboratory rearings of a German population at a constant 14°C: many eggs yielded normal adults after about 120 days. Larval growth rates were up to 2.2% body length day^-1, much higher than for English Nemurella (unimodal emergence), or any other stonefly. The thermal sum (degree-days above 0°C) accumulated between the two emergence peaks, at the German sites studied, resembled cumulated degree-days in a laboratory culture. For an Austrian population with trimodal emergence, degree-days accumulated in the field were lower, suggesting a lower temperature demand and partial trivoltinism. This is the only case of confirmed plurivoltinism in Plecoptera. Nemurella pictetii seems to have lost seasonal life cycle cues, enabling the opportunistic use of favourable local conditions. Population synchrony appears to be regulated by the thermal demand for development and the emergence threshold temperature.     

Hatching time and growth of Nemurellapictetii (Plecoptera: Nemouridae) in the laboratory and a Lake District stream

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.     

The temperature dependence of embryonic and larval development in Protonemura intricata (Plecoptera: Nemouridae)

SUMMARY. 1. Egg development and larval growth of Protonemura intricata (Ris, 1902) (Plecoptera: Nemouridae) were studied in the laboratory and in the Breitenbach, a small stream-in Germany (F.R.G.). 2. The mean number of eggs in batches collected from the field was 627 (S=314). 3. Mean batching success in the laboratory was 60–100% at 2–18°C. Cumulative hatch in individual batches could be described by asymmetrically sigmoid curves. The length of the hatching period was positively correlated with the length of the incubation period. 4. The incubation period of I', intricata normally consists of an initial dormancy followed by subsequent development. The length of embryonic development (Y. days) is strongly inversely temperature (T, °C) dependent and can be described by the equation: 5. The length of dormancy is dependent on oviposition dale, and is shorter the later that the eggs are laid. It also depends on temperature during incubation and is increased by rising temperatures. As a consequence, larvae hatch more or less synchronously in the field during autumn. Total incubation period, i.e. dormancy and actual development, exhibits a complex dependence on both incubation temperature and oviposition date. Under constant laboratory temperatures, a late sharp fall in temperature can terminate dormancy earlier. 6. Photoperiod probably induces dormancy and may already act on the last larval instars of the parent generation. The dormancy of P. intricata is classified as an oligopause (Müller. 1970, 1976). 7. In the laboratory. P. intricata larvae from early batches with long dormancy grew faster than larvae from late batches with direct development. Final size was the same in both cases. This acted against the population synchrony induced through egg dormancy. Benthos samples suggest the same in the field. 8. Avoidance of the suboptimal summer conditions in streams by the cold stenothermous P. intricata is suggested to partly explain the success of the species, which contributes more to total emergence biomass than do other Plecoptera in the Breitenbach.     

Life cycle of three stonefly species (Plecoptera) from an Apenninic stream (Italy) with the description of the nymph of Nemoura hesperiae

The life cycles of Isoperla grammatica, Amphinemura sulcicollis and Nemoura hesperiae are studied in a Northern Italy stream, sited in the Apennines. The three species show a univoltine life cycle and their development coincides approximately in the same period of the year, although the one of I. grammatica is longer. Possible egg dormancy could exist in the A. sulcicollis and N. hesperiae life cycles, but this needs to be proved. The three taxa show a spring flight period in the study area. Growth is almost constant through the life cycle, except in A. sulcicollis in which an increase is observed at the end of the development. N. hesperiae exhibits a faster growth than the other species. In addition, in this paper, the nymph of N. hesperiae is described and designed for the first time.     

Life history adaptation along a latitudinal cline in the water strider Aquarius remigis (Heteroptera: Gerridae)

We addressed the general hypothesis that life history differences among eastern populations of the North American water strider, Aquarius remigis (Heteroptera: Gerridae), along a north-south gradient are manifestations of genetic differentiation due to natural selection. We raised offspring of two field-caught populations from each of three latitudes in a common laboratory environment at 20° C and two photoperiods. Nearly all Quebec (PQ) individuals (ca. 46° N) entered diapause to reproduce the following spring (univoltine life cycle), while intermediate proportions of New York (NY; ca. 43° N) and New Jersey (NJ; ca. 41° N) individuals reproduced directly, producing a second generation (bivoltine life cycle). PQ females were smaller, developed faster, and laid smaller eggs than NY and NJ individuals; NY and NJ populations differed little in these variables. NY females had longer life spans than either PQ or NJ females, but lower oviposition rates. Total reproductive output did not differ across latitudes. Photoperiod affected body length, development time, and reproductive pathway, resulting in a latitude by environmental interaction. PQ individuals reproduced directly under 15L : 9D (summer) conditions only, while the NY and NJ populations exhibited more direct reproduction under 13L : 11D (spring or fall) conditions. Some life history characters of the NY and NJ populations displayed the higher variability indicative of phenological transition zones. These results indicate local adaptation of populations to long-term climatic patterns. Water striders appear to adapt to longer seasons by extending development, growing larger, and breeding directly. Larger body size and extended or rapid development are associated with bivoltinism and increase in egg size, but not necessarily with higher fecundity or oviposition rate. The phenological transition zone appears to be unrelated to a transition zone a little further south established by allozyme data and morphology, as all populations studied here could be electrophoretically identified as northern "type".     

Variability In the rate of egg development of the stonefly, Nemoura cinerea (Plecoptera)

SUMMARY. 1. The egg development of the widely distributed European stonefly. Nemoura cinerea Retzius. was investigated in the laboratory. There was a significant relationship between water temperature (T°C) and incubation period (Ydays), expressed by the regression equation: Y = 239 T^−0.85 (r²= 0.85. P<0.001).
2. The number of day-degrees above 0°C required for hatching showed a curvilinear relationship with water temperature, with a minimum requirement around 12°C.
3. Nemoura cinerea shows more variation in the rate of egg development than most other stoneflies. This, in part, explains the wide size range in nymphal populations and the species' extended emergence period. Flexibility in life cycle and asynchrony in egg development enable this species to colonize a wide range of freshwater habitats.     

A New Species of Mesonemoura from Yunnan: Mesonemoura sbordonii sp.n. (Plecoptera: Nemouridae)

Mesonemoura sbordonii, a new species of Nemouridae (Plecoptera) from Yunnan (China) is described. Remarks on its relationships with the closest species, M. vaillanti, are given.     

Behaviour and growth of dragonfly larvae along a permanent to temporary water habitat gradient

Abstract.  1. Freshwaters form a gradient from small temporary waters to large permanent waters. Identifying and examining traits that restrict the distribution of species along this gradient are crucial to the understanding of community structure in these habitats.
2. Using dragonfly larvae species, differences in traits important for growth and survival were studied.
3. The traits were studied in a series of laboratory experiments using two pairs of dragonfly species that coexist in the Namibian semi-desert. One species pair was from the most temporary part of the water permanence gradient and the other species pair from an intermediate part of the gradient.
4. As predicted, activity, capture rate, and growth rate were significantly greater in the two temporary water species. Contrary to the prediction made in the work reported here, species differences in microhabitat selection were not related to the species' habitat origin. Cannibalism did not differ between species.
5. The results lend support to the hypothesis that selection has favoured certain combinations of trait values and that these traits are important for a successful life in temporary and permanent waters.     

Differences in protein expression among five species of stream stonefly (Plecoptera) along a latitudinal gradient in Japan

Proteome variation among natural populations along an environmental gradient may provide insights into how the biological functions of species are related to their local adaptation. We investigated protein expression in five stream stonefly species from four geographic regions along a latitudinal gradient in Japan with varying climatic conditions. The extracted proteins were separated by two‐dimensional gel electrophoresis and identified by matrix‐assisted laser desorption/ionization of time‐of‐flight (MALDI TOF/TOF), yielding 446 proteins. Low interspecies variation in the proteome profiles was observed among five species within geographical regions, presumably due to the co‐occurring species sharing the environments. However, large spatial variations in protein expression were found among four geographic regions, suggesting strong regulation of protein expression in heterogeneous environments, where the spatial variations were positively correlated with water temperature. We identified 21 unique proteins expressed specifically in a geographical region and six common proteins expressed throughout all regions. In warmer regions, metabolic proteins were upregulated, whereas proteins related to cold stress, the photoperiod, and mating were downregulated. Oxygen‐related and energy‐production proteins were upregulated in colder regions with higher altitudes. Thus, our proteomic approach is useful for identifying and understanding important biological functions related to local adaptations by populations of stoneflies.     

Ecological species replacement of Liolaemus lizards along a habitat gradient

Summary Ecological species replacement of Liolaemus platei by Liolaemus lemniscatus appears to occur along a north-south oriented herb density gradient. Both congeners are the only ground-dwelling lizards in the area; this suggests that L. lemniscatus is an ecological counterpart of L. platei in herbaceous habitats. Relatively longer legs appear to be associated with the utilization of herb-free habitats by L. platei; the shorter legs possessed by L. lemniscatus are associated with the utilization of habitats of higher herb density. Morphological evidence indicates the presence of intermediate populations in the zone of intermediate herb density. Alternatives of a single-species cline versus interspecific hybridization between the two taxa are discussed.