Веснянки Веснянки: рост в ручьях, Англия

Веснянки: дрифт, выбор убежищ.

OECOLOGIA 1995, Vol 103, Iss 1, pp 1-9

Abstract:

Patch structure in sandy, compared to rocky streams, is

characterized by isolated snags that can only be colonized by

drifting. By measuring drift from patches (snags) of various

quality we determined the factors that influence habitat

selection and drift of the predaceous stoneflies Acroneuria

abnormis and Paragnetina fumosa. The presence of refugia (loose

bark and leaf packs) was more important than hunger level and

modified the effects of increased predator densities and

aggressive interactions. Stoneflies concentrated to 8x natural

densities with access to refugia remained longer on snags than a

single stonefly without access to refugia. During periods of

activity, refugia were defended with larger stoneflies always

displacing smaller nymphs. During long periods of inactivity,

two and sometimes three nymphs would rest side-by-side sharing

the same refuge. Hunger level (starved versus satiated

stoneflies), an indirect measure of a predator's response to

prey availability, had no significant effect on drift or habitat

selection regardless of the presence of refugia. Stonefly

predators had a uniform distribution while their prey were

clumped. Drift was deliberate and almost always delayed until

night, usually at dusk or dawn. An examination of previous

research plus the results of this study suggest that non-

predatory intra- and interspecific interactions can be an

important mechanism causing drift in streams.

Веснянки: местообитания, сезонная динамика.

ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA 1994, Vol 87, Iss 3, pp 321-326

Личинки веснянок собирались с коряг (woody debris) и донных субстратов в 3 реках Арканзаса с февраля 1991 по февраль 1992. Обнаружены следующие эффекты. Плотность веснянок больше на дне, чем на корягах, и больше зимой и весной, чем летом и во время дождей (fall). Найдены корреляции между типом местообитания и сезоном. Плотность зимних видов веснянок (seasonal density of winter stoneflies) больше при низкой температуре, быстром течении и большом количестве кислорода. Плотность видов веснянок с slow univoltine, semivoltine и fast univoltine весенними и летними жизненными циклами не обнаруживает значимой связи с этими факторами. Большинство видов, населяющих коряги, найдены на корягах с гнилой корой (loose bark) или разложившихся корягах с обширными щелями (interstitial spaces). Prostoia completa была единственным видом, чья плотность положительно связана с развитием обрастаний на корягах (biofilm volume). Таким образом, донные биотопы предпочтительны для большинства веснянок, но и коряги - важный биотоп для некоторых видов.

Abstract:

Plecoptera nymphs were collected from coarse woody debris (CWD) and benthic habitats from the White River, Illinois River, and Clear Creek of Northwest Arkansas from February 1991 through February 1992. Two-way analysis of variance comparing habitat type and season showed significant main effects. Densities were significantly greater in benthic habitats than on CWD and greater during winter and spring than during summer and fall. Significant two-way interactions were found between habitat type and season. Multiple regression analysis revealed a significant relationship among the seasonal density of winter stoneflies and flow rate, water temperature, and dissolved oxygen; densities increased as water temperature decreased and as dissolved oxygen concentration and flow rate increased. Densities of stonefly species with slow univoltine, semivoltine, or fast univoltine spring and summer life cycles showed no significant relationship with these factors. Two-way analysis of variance indicated that most species inhabiting coarse woody debris are found on wood with loose bark or wood that is well decayed and has many interstitial spaces. Prostoia completa (Walker) was the only species whose abundance was influenced by the volume of biofilm present on CWD and increased biofilm volume led to increased density. These results suggest that benthic habitats are preferred by most species of Plecoptera, but that CWD may also be an important habitat type for some species.

Веснянки: движение и пищевая активность.

Volume 25 Issue 1 Page 26 - February 2000

J. M. Elliott

1. The hypothesis under test was that larvae of Dinocras cephalotes (Curtis), Perla bipunctata Pictet, Isoperla grammatica (Poda), and Perlodes microcephalus (Pictet) differed markedly in their diel activity and feeding patterns. Mature larvae collected about 1month prior to adult emergence were used either for gut analyses or for observations of their activity and feeding patterns in three stream tanks with natural substrata and glass bottoms, so that activity could be observed above and below the substratum. A dull red light was used for observations in the dark. Food (larvae of Ephemeroptera, Simuliidae, and Chironomidae) was provided in excess.

2. Larvae for gut analyses were taken 1h before dusk or dawn (n=30 larvae per species for each day or night sample). The only species with food in the gut for the day samples was P. microcephalus. All species fed at night, the mean number of prey per larva being very similar for D. cephalotes, P. bipunctata, and I. grammatica but significantly higher for P. microcephalus. Most prey were insect larvae, especially Simuliidae and Chironomidae.

3. Diel activity patterns of single larvae differed interspecifically but not intraspecifically. Larvae of D. cephalotes and P. bipunctata were rarely active during the day; their activity increased at dusk and decreased at dawn, and was highest during the night; their success at prey capture was highest at dusk and dawn, with an ambush rather than a search strategy. Isoperla grammatica was rarely active during the day, most active at dusk and dawn when prey capture was highest, using a search strategy, and less active for the rest of the night. Perlodes microcephalus was active during the day, but only below the substratum, and very active from dusk to dawn with a high prey-capture success, using a search strategy. These experiments provided support for the hypothesis under test. The discussion concludes that the results could also help to explain known differences in growth rate and the length of the life-cycle in these four species.

Веснянки: экология личинок Pteronarcys.

Addresses: UNIV-GEORGIA, DEPT ENTOMOL, ATHENS, GA 30602, USA

Abstract:

1. Individually tagged Pteronarcys californica (Newport) nymphs were caught and recaptured over a 3-month period to determine their movement patterns and home range size. Sex/age structure, population density, and food habits (from gut contents) were also recorded. More than 1000 nymphs were tagged of which 256 (25%) were recaptured at least once. Tagged insects were confined to contiguous fast water, cobble riffles. Low velocity, silt-bottomed pools acted as barriers.

2. This stonefly has a 3-year life cycle although only the two oldest nymphal size-classes were tagged. Females were larger than males at all ages. The population sex ratio was skewed 60:40 towards females. Densities averaged 1.7 m-2 +/- 0.17 SE (range 0-19 m-2).

3. Most movements were short, indicating that a majority   of the stoneflies stayed within a few metres of their first capture point (mean 1.8 m downstream +/- 0.51 SE, range 44 m downstream to 40 m upstream). Significant patch size is a stream reach 24 m long that would contain 85% of the average individual's movements. Time between captures averaged 16 d +/- 0.734 SE (maximum 81 d). Eight individuals were notable for   extremely rapid upstream movements ranging from 6 to 22 m d-1. 

4. Frequency of movements up and downstream differed   significantly between the sexes. Pteronarcys distribution was   clumped with certain quadrats representing 'zones of   attraction.' The stoneflies moved rapidly between zones, then   stayed many days in those areas. Movements differed   significantly from random walk models. 

5. Guts contained 75% diatoms, 15% vascular plant material, and 8% animal remains. Females ate significantly more diatoms than males on a volumetric basis.

Веснянки

Source: AMERICAN MIDLAND NATURALIST 1991, Vol 125, Iss 1, pp 47-54

Four 1 m2 box-emergence traps were positioned over four

substrates (boulder, cobble, gravel and sand) in a section of

riffle and an associated pool in the Roseau River. Sampling was

conducted during the open water seasons of 1976 and 1977 and

traps were emptied every 2nd day. Eighteen hundred and eighteen

stoneflies representing seven species, and 412 stoneflies

representing six species were caught in 1976 and 1977,

respectively. The reduction in density and numbers of species

in 1977 is postulated to be the result of a drought in late

1976.

1976 as a result of higher spring water temperatures in 1977.

Stonefly emergence date could be predicted from the sum of

degree-days in the spring of their emergence year. Most

emergence occurred at night or in the morning but a few

individuals emerged during the brightest part of the day.

Numerical abundance for most species was highest over

larger substrates (boulder and cobble) in 1976, whereas in 1977

an unexpectedly large number emerged over smaller substrates

(gravel and sand).

Веснянки: выбор местообитаний.

Authors: Hassage-RL Stewart-KW

Title: Use of Substrate Volume and Void Space to Examine the Presence of 3 Stonefly Species (Plecoptera) Among Stream Habitats

Source: ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA

1991, Vol 84, Iss 3, pp 309-315

Seasonality of habitat use among the dominant stonefly

species Isoperla fulva Classen, Triznaka signata (Banks), and

Prostoia besametsa (Ricker) in a New Mexico mountain stream is

examined using interstitial volume (void space), water

temperature, and current. Interaction of these variables with

individual size (growth) was important in explaining the

abundance of these species. Abundance was calculated as number

of individuals per liter of substrate (sample volume). The use

of sample volume permitted the comparison of biotic density

between organic and mineral substrates. Void space and sample

volume of leaf packs were highly related (r2 = 0.83 and 0.90,

respectively; P < 0.001) to leaf pack dry weight.

Веснянки, жизненные циклы.

Authors: Harper-PP Lauzon-M Harper-F

Title: Life-Cycles of 12 Species of Winter Stoneflies from

Quebec (Plecoptera, Capniidae and Taeniopterygidae)

Source: CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE

1991, Vol 69, Iss 3, pp 787-796

The life cycles of 12 species of winter stoneflies

belonging to the families Capniidae and Taeniopterygidae were

studied in six river systems (seven sampling sites) in southern

Quebec. Eight of the cycles were previously undescribed. All

species were univoltine. Adults emerged as soon as the ice

broke on the streams in late winter, except for Paracapnia

angulata, Taenionema atlanticum, and Strophopteryx fasciata,

which emerged about 3 weeks later. The simplest cycle occurred

in Paracapnia opis, and P. angulata: egg development was direct

and nymphal growth proceeded steadily from May to January. All

other species showed evidence of a nymphal diapause interrupting

development between June and September. In Allocapnia pygmaea,

A. recta, C. vernalis, Taeniopteryx maura, T. parvula, and

Oemopteryx glacialis, growth was completed by January, but A.

minima, A. maria, Taenionema atlanticum, and Strophopteryx

fasciata continued to develop through the winter and reached

maturity just before emergence. Allocapnia recta, the first

species to emerge, was also the first to mature, but the

population showed much variability and the last nymphs to emerge

were probably the only ones to survive and reproduce under

Quebec climatic conditions.

Веснянки: питание Perlodidae.

Authors: Peckarsky-BL

Title: A Field-Test of Resource Depression by Predatory Stonefly Larvae

Source: OIKOS 1991, Vol 61, Iss 1, pp 3-10

Experiments were conducted in two Rocky Mountain streams

(Gunnison County, Colorado) to determine the context within

which predatory stonefly larvae locally depress their prey

populations. In feeding trials where no migration of prey

(Baetis bicaudatus, Ephemeroptera) was allowed from flow-through

boxes containing natural substrates, Megarcys signata and

Kogotus modestus (Perlodidae) significantly depressed prey

densities over 14 and 38 h, respectively. However, increasing

predator density had no apparent effect on per capita predation

rate. In 1984 enclosure experiments allowing prey but not

predator migration, Kogotus significantly reduced total prey

density and that of two relatively sedentary prey species

(Cinygmula mimus, Ephemeroptera, Heptageniidae, and Zapada

haysi, Plecoptera, Nemouridae) during three-day trials. After

six and nine days, prey colonization swamped the effects of prey

resource depression. In contrast, in 1985 three-day enclosure

experiments allowing prey but not predator migration, Kogotus

did not depress total prey densities nor those of any individual

prey taxon at densities of one, two, or four predators per cage;

nor did predators affect the size distribution of any prey taxa.

These data indicate that local prey resource depression by

predatory stoneflies may be unusual in these streams, as long as

prey are allowed to migrate into or out of containers (patches)

with predators. Densities of mobile prey species are, thus,

less depressible than are more sedentary prey species. The

observation that very high predator densities had effects on

their prey resource no different from those of low predator

densities is consistent with the hypothesis that exploitative

competition is less important than behavioral interference

between stoneflies, documented by other studies as a determinant

of the distribution and abundance of predatory stoneflies in

streams.

Веснянки: механизмы конкуренции личинок.

Authors: Peckarsky-BL

Title: Mechanisms of Intraspecific and Interspecific

Interference Between Larval Stoneflies

Source: OECOLOGIA 1991, Vol 85, Iss 4, pp 521-529

Behavior of focal individuals of two potentially competing

sympatric stonefly species, Megarcys signata and Kogotus

modestus (Perlodidae), was videotaped in flow-through plexiglass

arenas placed in the East River, Gunnison County, Colorado.

Focal individuals were observed alone and in pairs with

conspecifics and allospecifics at four prey (Baetis bicaudatus,

Baetidae, Ephemeroptera) densities to determine whether

competitors and prey resource levels affected prey capture

rates. Presence of conspecific or allospecific competitors

reduced stonefly prey capture rates, especially for Kogotus, the

smaller of the two species, due to a significant decline in

predator-prey encounter rates with competitors present. This

competitive effect was not observed at the lowest and highest

prey densities due to very low or very high predator-prey

encounter rates, respectively. Thus, interference affected

feeding rates only at intermediate prey densities. Competitors

had no effect on the probability of attacks per prey encounter

or capture success per attack. Within each stonefly species the

effects of intra- and interspecific interference on feeding

rates were similar, even though behavioral responses by both

stoneflies to interspecific encounters were more frequent than

to encounters with conspecifics. Kogotus showed the highest

levels of response to encounters with other stone-flies,

maintaining those high levels of response to Megarcys over all

prey densities. Further, male Kogotus, which are the smaller

sex, responded more frequently to competitive interactions than

did females. These data are consistent with the hypothesis that

interspecific interference was asymmetrical with Megarcys, the

larger species, being the superior competitor.

Веснянки: межвидовая конкуренция.

Authors: Peckarsky-BL Cowan-CA

Title: Consequences of Larval Intraspecific Competition to

Stonefly Growth and Fecundity

Source: OECOLOGIA

1991, Vol 88, Iss 2, pp 277-288

Language: English

Document type: Article

Addresses:

CORNELL-UNIV, DEPT ENTOMOL, ITHACA, NY 14853, USA

ROCKY-MT-BIOL-LABS, CRESTED-BUTTE, CO 81224, USA

Author keywords:

Body Size; Competition; Fecundity; Growth Rate; Stoneflies

Keywords Plus:

AGE-DEPENDENT INTERFERENCE; AEDES-AEGYPTI; EXPLOITATIVE

COMPETITION; POPULATION-DYNAMICS; PREY DENSITY; ODONATA;

COENAGRIONIDAE; PLECOPTERA; BEHAVIOR; STREAM

Abstract:

We conducted experiments in replicated circular streams to

measure the effect of intraspecific larval density on growth

rates, size at emergence, timing of emergence, and fecundity of

two species of predatory stoneflies (Megarcys signata and

Kogotus modestus, Perlodidae). Early instars of both species

showed no significant effect of intraspecific larval density on

mean growth rates, despite the observation that in the absence

of competitors stoneflies ate on average, significantly more

prey (Baetis bicaudatus, Ephemeroptera, Baetidae) than in the

presence of competitors. However, larval size of stoneflies

held at higher densities (two per chamber) diverged over time,

resulting in a greater size variability (coefficient of

variation) among Kogotus than in treatments with low densities

of stoneflies (one per chamber). The effect of doubling the

density of early-instar Megarcys larvae was also asymmetrical,

resulting in one larger and one smaller individual. In

contrast, doubling the density of last-instar stoneflies whose

feeding rates declined significantly prior to emergence had few

measurable consequences, except that male Megarcys, which

continued to feed throughout the last instar, had lower average

feeding rates in high-density than in low-density chambers, and

emerged at a significantly smaller mean size. We conclude that

competition between early-instar stonefly larvae results in an

asymmetry of body sizes, but that competitive effects are

reduced as larvae slow or cease feeding before emergence. Since

larger females of both stonefly species produced more eggs, the

probable cost to females of early-instar larval competition was

a reduction in their potential contribution of offspring to the

next generation. The cost of attaining a smaller body size for

male stoneflies is unknown; but if, as in many other insects,

larger males have greater reproductive success, larval

competition may increase the opportunity for sexual selection

among males. This hypothesis remains to be tested

experimentally.

Веснянки: Austroperlidae.

Authors: Albarino-RJ

Title: The Food-Habits and Mouthpart Morphology of a South

Andes Population of Klapopteryx Kuscheli (Plecoptera,

Austroperlidae)

Source: AQUATIC INSECTS

2001, Vol 23, Iss 3, pp 171-181

The food habits of two size groups of larvae of Klapopteryx

kuscheli, belonging to intermediate and late instars, were

studied for mouthpart morphology, gut content and were tested in

food particle size preference experiments. Gut content of 103

larvae collected seasonally (in April, July, October and January

1996-97) in a 1(st) order mountain stream in Argentina was

determined. Particle size preference experiments consisted of

offering simultaneously to each larval size group fine (FPOM)

and coarse (CPOM) particle sizes of Nothofagus pumilio leaves.

Mouthparts are characterized by stout mandibles bearing both

cutting teeth and a well-developed molar region. The gut content

of K. kuscheli in all seasons was dominated by leaf fragments

(sizes from 0.5 mum to 1 mm), representing annually 79.9% and

83.4% of the gut content, respectively, for intermediate and

late instars. In particle size preference experiments both

larval size groups fed selectively on CPOM; those of

intermediate instars consumed 6 times and those of late instars

4 times more CPOM than FPOM. Therefore, both groups of K.

kuscheli larvae are functionally classified as shredders,

preferring coarse particle size.

жүктеу/скачать 1.21 Mb.

Достарыңызбен бөлісу: