Intra- and Interspecific Differences in the Response of Two Lentic Species of Leeches to Seasonal Hyperoxia

1991 ◽  
Vol 48 (6) ◽  
pp. 1124-1127 ◽  
Author(s):  
Ronald W. Davies ◽  
T. E. Gates
Keyword(s):  
Reproductive Success ◽  
Seasonal Movements ◽  
Percent Survival ◽  
Size Classes ◽  
Interspecific Differences ◽  
Nephelopsis Obscura ◽  
Microhabitat Distribution ◽  
Flow Through ◽  
Ecological Success ◽  
Higher Temperature

Intra- and interspecific differences in survivorship of Nephelopsis obscura and Erpobdella punctata exposed to hyperoxia (200 or 300%) at spring (5 °C) and summer (20 °C) water temperatures were examined in a flow-through system. In general, percent survival and time of 50% survival increased with leech size and decreased with higher temperature for both species. All size classes could survive the maximum recorded duration of hyperoxia in the spring, and we conclude that spring hyperoxia probably does not directly affect the ecological success or microhabitat distribution of either species. At 20 °C, medium and large E. punctata had much higher survivorship than N. obscura. As summer hyperoxia can last for 30 d, these differences could contribute to changes in numerical dominance. Intra- and interspecific differences in response to hyperoxia may also influence seasonal movements between different microhabitats of different size classes of N. obscura and E. punctata. We suggest that seasonal and annual variability in littoral hyperoxia regimes can differentially influence the survivorship, reproductive success, and microhabitat distribution of many macroinvertebrates.

Assessment of Activity-Specific Metabolism of Aquatic Organisms: An Improved System

1992 ◽  
Vol 49 (6) ◽  
pp. 1142-1148 ◽  
Author(s):  
Ronald W. Davies ◽  
Frederick J. Wrona ◽  
V. Kalarani
Keyword(s):  
Oxygen Consumption ◽  
Individual Variation ◽  
Aquatic Organisms ◽  
Size Classes ◽  
Interspecific Differences ◽  
Nephelopsis Obscura ◽  
Highly Sensitive ◽  
Similar Weight ◽  
Flow Through

An improved flow-through respirometer capable of assessing activity-specific metabolism of aquatic organisms is presented and assessed. The system is highly sensitive and versatile, since it continuously monitors and records activity-specific oxygen consumption readings for periods up to 72 h and is capable of detecting differences in metabolism of individual specimens of similar weight. Using this system, we demonstrated individual variation and intraspecific differences in metabolism between two size classes of the freshwater leech Nephelopsis obscura and interspecific differences between N. obscura and another freshwater leech, Erpobdella montezuma, and compared these findings with the metabolism of the amphipod Hyalella montezuma.

Reproductive success and growth of two species of Erpobdellidae: the effect of water temperature

1987 ◽  
Vol 65 (5) ◽  
pp. 1253-1256 ◽  
Author(s):  
Frederick J. Wrona ◽  
L. R. Linton ◽  
Ronald W. Davies
Keyword(s):  
Reproductive Success ◽  
Water Temperature ◽  
Growth Rates ◽  
Hatching Success ◽  
The Other ◽  
Cocoon Production ◽  
Lotic Ecosystems ◽  
Interspecific Differences ◽  
Nephelopsis Obscura ◽  
The Mean

Cocoon production and hatchling growth of two species of Erpobdellidae (Nephelopsis obscura and Erpobdella punctata) were compared at different water temperatures (5–20 °C). Based on the mean number of cocoons produced per individual, mean numbers of eggs per cocoon, cocoon hatching success, and hatchling growth rates, E. punctata has an ecological advantage over N. obscura at 5 and 10 °C. At 15 and 20 °C, neither species displayed a clear advantage over the other in relation to production or growth of offspring. It is suggested that the observed interspecific differences may at least in part explain the numerical dominance of E. punctata in colder lotic ecosystems.

Reproductive Success of Amnicola limosa (Gastropoda) in Low Alkalinity Lakes in South-Central Ontario

1989 ◽  
Vol 46 (5) ◽  
pp. 863-869 ◽  
Author(s):  
Margo A. Shaw ◽  
Gerald L. Mackie
Keyword(s):  
Life Cycle ◽  
Reproductive Success ◽  
Hatching Success ◽  
Low Ph ◽  
Critical Stage ◽  
Percent Survival ◽  
South Central ◽  
Order Of Magnitude ◽  
Magnitude Difference

The reproductive success of the gastropod Amnicola limosa was examined in six lakes ranging in pH from 4.62 to 7.42 to determine which stages in the life cycle were most sensitive to acidification. Although fecundity was significantly greater (p < 0.01) for adults reared at pH 7.42 than at pH 5.89–6.64, a failure to oviposit was documented only at pH 4.62. Hatching success was uniformly high (88–97%) at pH 5.59 to 7.42, while embryos incubated at pH 4.62 suffered complete mortality. The most critical stage in the life cycle is the newly hatched stage. Survival during the 20 d post hatch ranged from 23% at pH 5.59 to 69% at pH 7.42. There was an order of magnitude difference in the cumulative percent survival of recruits in lakes ranging in pH from 5.59 (5.1%) to 7.42 (44.0%). Juveniles raised at low pH (5.59–5.70) were on average 0.20 mm (20%) smaller than those in circumneutral lakes (pH 6.64–7.42). The present low densities of Amnicola limosa in Heney Lake (pH 5.59) can be explained by low recruitment since 1980. Evidence presented suggests that the disappearance of this species from clear low pH lakes (pH < 5.8) is due to reductions in fecundity and hatchling survival.

scholarly journals Air Temperature Rises in Compressor and Turbine Stator Wells

1994 ◽  
Author(s):  
F. J. Bayley ◽  
P. R. N. Childs
Keyword(s):  
Fluid Dynamic ◽  
Axial Flow ◽  
Labyrinth Seal ◽  
Published Data ◽  
Flow Conditions ◽  
Turbine Stator ◽  
Substantial Temperature ◽  
Feasible Range ◽  
Flow Through ◽  
Higher Temperature

This paper considers the fluid dynamic principles determining the consequences of mainstream fluid ingressing to the comparatively shallow space between the rotor disc and the ring used in many designs of axial-flow turbo-machine, especially compressors, to support the stator blades at their inner ends. Windage power due to friction between this fluid and the bounding walls of this annular space, or ‘stator well’, can lead to substantial temperature rises in this region. The feasible range of flow regimes is first developed, especially as influenced by leakage through the internal seals beneath the stators separating adjacent wells. Using published data, on windage coefficients and the effects of geometry on the flow through the wells, very little of which has been obtained from truly representative flow conditions or geometries, calculations have been made to estimate the likely rises in temperature to be anticipated in realistic well designs. Leakage rates appear, not unexpectedly, to be crucial in determining these temperature rises, but the geometries of the system are little less critical, in particular the ratio of the outer to inner radiuses of the stator well and the outer peripheral clearances between rotor and stator surfaces. Leakage into a well from its adjacent neighbour is shown to lead to higher temperature rises downstream of the labyrinth seal and the possible effects of recirculation through stator wells from the mainstream boundary layer could be significant.

Predation on the erpobdellid leech Nephelopsis obscura in the laboratory

1989 ◽  
Vol 67 (11) ◽  
pp. 2689-2693 ◽  
Author(s):  
A. Cywinska ◽  
Ronald W. Davies
Keyword(s):  
High Abundance ◽  
Prairie Pothole ◽  
Size Classes ◽  
Nephelopsis Obscura ◽  
Consumption Rates ◽  
Predation Rates

Six size classes of Nephelopsis obscura ranging from cocoons through hatchlings (2–4 mg) to mature individuals (150 mg) were exposed to a range of potential predators and also tested for cannibalism. Neither cannibalism nor interspecific leech predation was found, but nine species of Coleoptera, Amphipoda, Hemiptera, and Zygoptera consumed one or more size classes of N. obscura. In general, predation rates were highest on individuals <10 mg and declined with increasing size of N. obscura. Larger predators (intra- and inter-specifically) usually had higher consumption rates than smaller ones. Because of the high abundance of the nine species of predators in prairie pothole lakes during the summer, it is speculated that predation on N. obscura hatchlings and cocoons is directly related to the recorded reductions in these size classes in the macrophyte zones during the summer.

Influence of Overwintering Stresses on Respiration Throughout the Life History of the Freshwater Leech, Nephelopsis obscura

1993 ◽  
Vol 50 (4) ◽  
pp. 841-845 ◽  
Author(s):  
Ronald W. Davies ◽  
V. Kalarani
Keyword(s):  
Life History ◽  
Oxygen Consumption ◽  
Dry Weight ◽  
Low Oxygen ◽  
Nephelopsis Obscura ◽  
Stage 4 ◽  
Metabolic Costs ◽  
History Of ◽  
Flow Through ◽  
Low Oxygen Concentration

The effects of overwintering stresses (low temperature, low oxygen concentration) on the life history patterns of activity-specific oxygen consumption by Nephelopsis obscura were determined using a flow-through respirometer system and compared with leeches hatched and maintained under summer conditions. While resting and active oxygen consumption increased with body dry weight, weight-specific resting (Rm) and active (Ra) oxygen consumption and aerobic scope (AS) decreased with increase in body weight in both winter and summer N. obscura. Rm in winter leeches was higher than in summer leeches, probably reflecting the higher metabolic costs of tissue repair and maintenance after winter stresses. Although Ra and AS in winter leeches were initially lower than in summer leeches, by stage 4, compensation in winter leeches was complete and by stage 6, over-compensation occurred. The effects of overwintering on oxygen consumption and AS persisted throughout the life history and help explain some of the differences in allocation of energy storage observed in winter and summer leeches.

scholarly journals Reproductive strategies of a population of a freshwater amphipod (Crustacea, Amhipoda, Hyalellidae) from southern Brazil

2018 ◽  
Vol 18 (2) ◽  
Author(s):  
Daniela da Silva Castiglioni ◽  
Morgana Taís Streck ◽  
Stella Gomes Rodrigues ◽  
Alessandra Angélica de Padua Bueno
Keyword(s):  
Body Size ◽  
Reproductive Success ◽  
Reproductive Strategies ◽  
Reproductive Period ◽  
Lower Probability ◽  
Southern Brazil ◽  
Size Classes ◽  
Cephalothorax Length ◽  
Males And Females ◽  
The Mean

Abstract: The aim of this study was to characterize the reproductive strategies of a population of Hyalella bonariensis from southern Brazil. Pairing success, reproductive period of males and females, fecundity, and body size at the onset of reproduction were evaluated. Animals were sampled four times (August 2012, October 2012, January 2013, and April 2013) with the 250 µm-mesh dip net during 20 minutes by only one person. In the field, precopulatory pairs and ovigerous females were individualized. In the laboratory, cephalothorax length (CL) were measured and eggs and juveniles were removed from the females' marsupium and counted. The mean CL of paired males and females was significantly higher than that of non-paired males and females. A sexual dimorphism in body size was observed in the population - both paired and non-paired males were larger than females. Probably larger males have a higher probability of losing females during precopulatory behavior. A significant correlation was observed between the size of paired males and females - larger males often paired with larger females and smaller males paired with smaller females (r = 0.81). The pairing success of males increased with body size and we can assume that males from all size classes are able to find mates. The pairing success of females was independent of body size - paired and non-paired females had similar mean CL. The reproductive success increased with body size in males and females, and was more evident in males. Females from the largest size classes had null reproductive success. The idea that larger females can produce more eggs but might have a lower probability of finding a mate than smaller females was corroborated by our results. Therefore, smaller females have higher pairing success because they are capable of mating with a higher percentage of males. The estimated mean fecundity of H. bonariensis was 17.4 (± 3.89) eggs/juveniles. Our results are similar to those of other species of Hyalella from Brazil.

scholarly journals Production effect of various feeds on two size classes of juvenile tench (Tinca tinca) under the conditions of intensive rearing

2007 ◽  
Vol 55 (1) ◽  
pp. 111-116 ◽  
Author(s):  
Jan Mareš ◽  
Jiří Jirásek ◽  
Vít Baránek ◽  
Jiří Fiala ◽  
Radovan Kopp
Keyword(s):  
Specific Growth ◽  
Nutrient Content ◽  
Conversion Ratio ◽  
Size Class ◽  
Feed Conversion ◽  
Tinca Tinca ◽  
Size Classes ◽  
Intensive Rearing ◽  
Flow Through ◽  
Tench Tinca Tinca

The experimental rearing of tench (Tinca tinca) juveniles of two size classes with initial individual weight of 0.8 and 1.2 g was performed into flow-through aquaria connected to recirculation system during a period of 63 days. Three feeds (KARPICO Supreme 7 Ex, ASTA 2, L05/CH) with nutrient content of 37/8, 42/7 and 35/7 (% proteins/ fat) were used in the experiment. Achieved values of production indicators – feed conversion ratio (FCR) and specific growth rate (SGR) ranged from 1.84 to 4.15 and from 0.70 to 1.49 %.d–1, respectively in relationship to the size class and feed used. More favourable values were achieved with the bigger size class regardless to the diet used (FCR 1.84–3.53 and SGR 0.83–1.49 %.d–1) and the best results were achieved when using ASTA 2 feed (2.05 and 1.84 or more precisely 1.36 and 1.49%.d–1).

On the Scaling of Aeroelastic Parameters for High Pressure Applications in Centrifugal Compressors

2016 ◽  
Author(s):  
Florian Fruth ◽  
Peter Jeschke ◽  
Holger Franz
Keyword(s):  
Reynolds Number ◽  
Density Ratio ◽  
Development Stage ◽  
Flow Coefficient ◽  
Mode Shapes ◽  
Centrifugal Compressors ◽  
Reynolds Number Effects ◽  
Flow Through ◽  
Higher Temperature ◽  
Temperature Levels

A centrifugal compressor has been evaluated numerically for the scalability of aeroelastic parameters for different pressure levels. By maintaining the flow coefficient, as done in the development process, comparable aerodynamics for the compressor cases have been generated ranging from 0.96 bar to 40 bar inlet pressure. It has been found, that the mean static pressure as well as the aerodynamic damping can be scaled by the inlet density ratio. The gained results proofed for this case to be sufficient in magnitude and distribution for an early development stage. Harmonic pressure scaling for centrifugal compressors however has resulted in non-negligible errors. The origin of changes for the setup presented is found in the variation of Reynolds number. Especially the hub and tip sections are influenced and therefore also the secondary flow through the impeller tip gap. This generally results in lower scalability after the transition from axial to radial flow. Hence impeller trailing edge mode shapes have to be considered carefully. The Reynolds number effects become smaller however for higher temperature levels, reducing the scaling errors.

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