Interactions of Adult Stoneflies (Plecoptera) with Riparian Zones II. Diet

The diets of three species of gripopterygid stonefly adults (Acroperla trivacuata, Zelandoperla decorata and Zelandobius furcillatus) from New Zealand were investigated using field studies and laboratory experiments. Guts of female stoneflies were generally fuller than those of males, suggesting that terrestrial feeding was particularly important for females. Adult A. trivacuata and Z. decorata collected from riparian vegetation had fuller guts than those collected from rocks, indicating that adults may move towards riparian vegetation to feed after emergence. Fungi and pollen formed the core food categories found in the guts of adult stoneflies collected from riparian vegetation. Stable isotope analyses of stoneflies and potential food sources collected from the near-stream riparian zone indicated that adult body carbon was derived primarily from autochthonous sources and/or from lichen growing on exposed stream channel rocks. The absence of mature females in our near-stream field collections may explain the lack of congruence between results of gut content and stable isotope analyses, as there would be a time lag between feeding following emergence and incorporation of any terrestrial carbon into body tissue. Assays for the presence of fructose were typically negative, even though pollen and sooty mould fungi were often ingested, probably because nectar or honeydew was rapidly assimilated after ingestion. Laboratory feeding trials indicated that adult Z. decorata lived significantly longer when fed a dilute sucrose solution than when fed a yeast extract solution or water. Our results demonstrate that terrestrial food sources are consumed by these adult gripopterygid stoneflies and that feeding is important for longevity. The provision of dietary requirements for the completion of adult aquatic insect life cycles may be an important consideration in riparian vegetation management. Dietary and assimilation studies of mature females which may move deep into riparian zones are required to resolve the strength of these linkages.     

Stoneflies (Plecoptera) in the diet of brook trout (Salvelinus fontinalis Mitchell) in Libby Creek,Wyoming, USA

The stonefly component of a naturally reproducing population of brook trout ( Salvelinus fontinalis) was studied by analyzing 216 stomach pump samples collected between May 15 and August 10, 1991 and 1992, from Libby Creek, an alpine stream in the Medicine Bow National Forest in Wyoming. Stoneflies constituted 10.3% of the total items recovered and were the second most abundant order in the samples. Nineteen species of Plecoptera representing five families were identified. Approximately 43% of all stoneflies were Sweltsa lamba; the next most prevalent species was Zapada haysi (12%). The other prevalent insect orders in the samples were Diptera (57.2%), Ephemeroptera (8.4%) and Trichoptera (6.1%). Terrestrial Coleoptera, Hymenoptera, and Hemiptera were most common in July and August. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adult feeding habits of three Perloidea species (Plecoptera: Perlidae and Chloroperlidae)

The gut content composition of three species of the superfamily Perloidea, Marthamea selysii (Pictet, 1842), Dinocras cephalotes (Curtis, 1827), and Siphonoperla torrentium (Pictet, 1842), from northwestern Spain is analyzed and described. The quantity of food found in all adults of M. selysii and D. cephalotes was very low. Spores of fungi and pollen of angiosperms were the most abundant components in the diet of M. selysii. Pollen of angiosperms, followed by fungal spores, detritus, and animal matter were the most abundant components in the diet of both sexes of D. cephalotes. The adult diet of both sexes of S. torrentium consists mainly of pollen and agrees with data of the previous studies on this same species in other areas. Our results also show that the consumption of animal matter could be a way to get a nutritional complement and is more common than previously considered in adult stoneflies. The obtained data support the hypothesis that adult feeding is less important for large stoneflies (as M. selysii and D. cephalotes) than for other smaller Perloidea (as S. torrentium), but feeding habits in these large Plecoptera could not be as negligible as previously supposed.     

Distribution Patterns,Species Assemblages and Habitat Selection of the Stoneflies (Plecoptera) from Two Mediterranean River Basins in Southern Spain

The stonefly distribution and its relationship with habitat changes, based on stream physico chemical features, were investigated in two Mediterranean river basins (Guadaira and Guadalete, S Spain). Plecopteran nymph distribution varied along an elevation gradient. Both stonefly species richness and species diversity increased with altitude. Stoneflies were able to tolerate a wide range of environmental conditions but were absent from low altitude sites, temporary streams with high salinity values and high water temperature. A total of 13 stonefly species were found in the study area, from which Tyrrhenoleuctra minuta (Klapálek ) and Protonemura sp. were dominant. The most widespread species were Nemoura lacustris and Capnioneura mitis. Three distinct species assemblages were observed according to their distribution patterns, but with similar environmental preferences. Capnioneura petitpierreae and T. minuta showed preferences to low altitude sites, whereas C. mitis and N. lacustris were found throughout all sites. T. minuta and N. lacustris inhabited permanent and temporary sites, while the same species and C. mitis also were found in semipermanent streams. Temporally, most stoneflies were caught during winter (85.9%), especially at the low altitude sites.     

Effects of insulin-like growth factor I (IGF-I) on enzymatic activity in human adrenocortical cells. Interactions with ACTH

Cells obtained from 6 adult human adrenals or adrenal fragments were cultured in serum-free synthetic medium (McCoy's) in order to study the isolated effects of IGF-I on steroidogenesis and its interactions with ACTH. After addition of peptide, changes in the activities of steroidogenic enzymes were assessed by measuring certain steroids in the spent medium. These included pregnenolone, 17-hydroxypregnenolone (17-OH-Preg), dehydroepiandrosterone (DHA), 17-hydroxyprogesterone (17-OH-P), androstenedione (AD), 11-deoxycortisol and glucocorticoids (chiefly cortisol and its immediate precursors, 11-deoxycortisol and 17-OH-P) and cortisol itself.

The steroid responses obtained with repeated doses of IGF-I (40 ng/ml ≈ 10⁻⁹ M), added at 0, 48 and 72 h, over 4 days' culture were quite different from those obtained with repeated doses of ACTH (0.25 ng/ml ≈ 10⁻¹⁰ M). All the steroids measured increased with time of culture under the influence of ACTH and, apart from pregnenolone which peaked, tended to reach a plateau. With IGF-I, by contrast, DHA, AD, 11-deoxycortisol and glucocorticoid production increased initially, then decreased progressively, whereas pregnenolone, 17-OH-Preg and 17-OH-P production was either absent or negative.

Cumulative steroid production over 4 days reached similar levels in response to a single dose of IGF-I and/or ACTH, with two major exceptions: pregnenolone dropped significantly with IGF-I [46% ± 6 (SEM) as opposed to 93% ± 11 with ACTH, P < 0.005, N = 5], as did 17-OH-P (48% ± 11 vs 113% ± 8 with ACTH, P < 0.001, N = 6). Increased formation of down-stream metabolites (DHA, AD, 11-deoxycortisol and glucocorticoids) would suggest that IGF-I induced stimulation of the 17-, 21- and 11β-hydroxylases.

The responses to ACTH stimulation of cells which 4 days previously had been pre-treated with an initial and single dose of IGF-I and/or ACTH emphasized the impact of IGF-I on the 3-hydroxylation steps in cortisol biosynthesis. Compared with ACTH pre-treatment, the effects of which faded in the long term, pre-treatment with IGF-I resulted in a significantly increased steroidogenic response (P between < 0.05 and < 0.01). With the single exception of pregnenolone (43% ± 4.7), production of all the metabolites was amplified: 17-OH-Preg: 348% ± 88; DHA: 643% ± 127; 17-OH-P: 193% ± 36; AD: 725% ± 200; 11-deoxycortisol: 573% ± 110; cortisol: 1000%.

Our findings strongly suggest that IGF-I plays a major rôle in the regulation of steroidogenesis by promoting and maintaining enzymatic activity (17, 21- and 11β-hydroxylases) via which the function of ACTH is achieved, viz., biosynthesis of cortisol.     

Effects of Interactions Between Low and High Temperature Treatments on Flowering of Spring Rape (Brassica napusvar.annua)

Exposure to high temperature (30 °C) before or after exposureto low temperature (0, 4 or 8 weeks at 4 °C) consistentlyincreased the number of leaf nodes at flowering and delayedflowering in a range of genotypes of spring rape(Brassica napusvar.annuaL.).Four days of prior exposure to high temperature had more effectthan 2 d, and the effect of subsequent exposure to high temperaturewas maximized when exposure commenced 1 week after the end ofthe low-temperature treatment. In genotypes that showed a vernalizationresponse (i.e. in which the number of leaf nodes at floweringwas reduced or flowering was advanced by low temperature), thisresponse was reduced or eliminated by either prior high-temperaturetreatment (antivernalization) or subsequent high-temperaturetreatment (devernalization). A biochemical model to accountfor these effects is proposed.Copyright 1998 Annals of BotanyCompany Brassica napusvar.annua, spring rape, antivernalization, devernalization, vernalization     

Effects of CO2 and Temperature on Tritrophic Interactions

There has been a significant increase in studies of how global change parameters affect interacting species or entire communities, yet the combined or interactive effects of increased atmospheric CO₂ and associated increases in global mean temperatures on chemically mediated trophic interactions are mostly unknown. Thus, predictions of climate-induced changes on plant-insect interactions are still based primarily on studies of individual species, individual global change parameters, pairwise interactions, or parameters that summarize communities. A clear understanding of community response to global change will only emerge from studies that examine effects of multiple variables on biotic interactions. We examined the effects of increased CO₂ and temperature on simple laboratory communities of interacting alfalfa, chemical defense, armyworm caterpillars, and parasitoid wasps. Higher temperatures and CO₂ caused decreased plant quality, decreased caterpillar development times, developmental asynchrony between caterpillars and wasps, and complete wasp mortality. The effects measured here, along with other effects of global change on natural enemies suggest that biological control and other top-down effects of insect predators will decline over the coming decades.     

Effects of Temperature and Relative Humidity on Development,Reproduction, and Predation in Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae)

The predatory gall midge Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) is a biological control agent for twospotted spider mites on greenhouse vegetable crops. Effects of temperature and relative humidity (RH) on development of immatures, reproduction, and prey capture were determined in order to confirm the suitability of F. acarisuga for use in greenhouses. Developmental time ranged from 10 days at 27°C to 34 days at 15°C. At 20°C, developmental time was significantly shorter at 96% RH than at 84% RH. There was very poor survival of immatures at 64% RH and none at 36%. Lifespan of adult females decreased with increasing temperature, but temperature had no significant effect on number of eggs laid. At 20°C, lifespan was longer at 84 and 96% RH than at 64 or 36% RH. The number of spider mites attacked by 3-day-old larvae over 8 h increased with increasing temperature from 15 to 27°C. The number of mites attacked also increased with increasing RH at 27°C. We conclude that F. acarisuga will complete its life cycle and reproduce under conditions typically found in vegetable greenhouses in northern temperate climates. However, extended periods of low RH (<60% RH) could reduce reproduction and survivorship sufficiently to impair the predator's action against spider mite populations.     

Notes on Plecoptera (19) Isoperla lugens (Klapalek, 1923), replaces I. alpicola Brinck, 1949

A male lectotype and several paralectotypes of Chloroperla lugens Klapálek, 1923 are designated. The species is transferred to genus Isoperla and is the valid name for Isoperla alpicola Brinck, 1949.     

Notes on Plecoptera (23). The Anchor of the Tetropina Egg (Plecoptera: Perlidae)

After a study of the type material of Baetis nexus Navás, 1918 and a comparison with Hungarian specimens of Baetis pentaphlebodes Ujhelyi, 1966 it is concluded that the two nominal species are synonyms and that B. nexus is the valid name.     

On Longevity of Adult Chaoborids (Diptera,Chaoboridae) under Sugar Feeding Conditions

Entomological Review - Longevity of the adult male and female Mochlonyx velutinus (Ruthe) and the adult male Chaoborus crystallinus (De Geer) that emerged under laboratory conditions was measured,...     

Effects of Atmospheric Humidity and Temperature on the Survival of Airborne Flavobacterium

The survival of airborne Flavobacterium sp. in particle sizes ranging from 1 to 5 μm was significantly influenced by atmospheric temperature. A progressive increase in temperature from −18 to 49 C resulted in increases in death rates of the airborne organism. The lowest death rates were observed in the temperature range of −40 to −18 C, and the highest death rates were observed in the 29 to 49 C range. At 24 C, the survival of airborne Flavobacterium did not appear to be significantly affected by relative humidity ranging from 25 to 99%.     

Interactions of Alcohols and Increased Air Pressure on Echinochloa crus-galli (L) Beauv. Seed Germination

In contrast to previous findings, where stimulation of E. crus-galliseed germination by n-propanol was reversed by simultaneoustreatment with 0.965 MPa air pressure, similar pressure wasunable to reverse stimulation by n-butanol. When pressure wasapplied up to 2 d prior to n-propanol, stimulation by n-propanolwas still prevented. Pressure appeared to exert its effect rapidly;only 15 min exposure gave the maximum effect. If temperatureduring treatment with pressure and n-propanol was 15 °C,rather than 35 °C, the inhibitory effect was not observed.The inhibitory action of pressure can persist but is not lethalsince drying the seeds after n-propanol and pressure treatmentrestored high levels of responsiveness to red irradiation. Theseseveral facts suggest that pressure may not simply prevent theaction of alcohols (anaesthetics) as previously thought, butmay have an action of its own, which may only be apparent uponinteraction with specific compounds, e.g. n-propanol. Phytochrome, anaesthesia, dormancy, membrane, Echinochloa crus-galli (L.) Beauv., barnyardgrass     

高温高湿胁迫下茉莉酸甲酯对紫苏种子萌发及生理特性的影响

以紫苏品系GS011种子为材料,在温度为50℃、空气相对湿度为95%、时间为12h的胁迫条件下,研究不同浓度(0.05、0.10、0.15、0.20和0.25mmol.L-1)茉莉酸甲酯(MeJA)对紫苏种子萌发、幼苗生长、叶片氧化损伤和抗氧化酶活性的影响。结果表明:0.15mmol.L-1 MeJA处理能显著缓解高温高湿对紫苏种子生长发育造成的胁迫伤害,使紫苏种子发芽率、发芽势、发芽指数、活力指数均达到最大值,分别为40.84%、31.83%、8.83和1.35;同时使其叶片MDA含量最低(0.15μmol.g-1),SOD、CAT、LOX、POD和APX活性均达到最大值,分别为0.27U.mg-1及4.7、5.7、4.9和8.9U.g-1.min-1。研究发现,MeJA在一定程度上能提高SOD等保护酶的活性,缓解高温高湿造成的氧化损伤,有效促进高温高湿胁迫下紫苏种子的萌发和幼苗生长。