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.

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.

Importance of individual species of predators on nesting success of ducks in the Canadian Prairie Pothole Region

1989 ◽  
Vol 67 (2) ◽  
pp. 291-297 ◽  
Author(s):  
Douglas H. Johnson ◽  
Alan B. Sargeant ◽  
Raymond J. Greenwood
Keyword(s):  
Nest Predation ◽  
Prairie Pothole Region ◽  
Individual Species ◽  
Prairie Pothole ◽  
Canadian Prairie ◽  
Vegetation Growth ◽  
Striped Skunk ◽  
Franklin's Ground Squirrel ◽  
Predation Rates ◽  
Activity Indices

We followed 3094 upland nests of several species of ducks. Clutches in most nests were lost to predation. We related daily nest predation rates to indices of activity of eight egg-eating predators, precipitation during the nesting season, and measures of wetland conditions. Activity indices of red fox (Vulpes vulpes), striped skunk (Mephitis mephitis), and raccoon (Procyon lotor) activity were positively correlated, as were activity indices of coyote (Canis latrans), Franklin's ground squirrel (Spermophilus franklinii), and black-billed magpie (Pica pica). Indices of fox and coyote activity were strongly negatively correlated (r = −0.51), as were those of badger (Taxidea taxus) and skunk (r = −0.46). Nest predation rates in the early part of the breeding season were positively related to indices of fox, American crow (Corvus brachyrhynchos), and badger activity. Predation rates in the latter part of the season were positively related to indices of fox and skunk activity. Predation rates on early-season nests were lower in areas and years in which larger fractions of seasonal wetlands contained water. For late-season nests, a similar relationship held involving semipermanent wetlands. We suspect that the wetland measures, which reflect precipitation during some previous period, also indicate vegetation growth and the abundance of buffer prey, factors that may influence nest predation rates.

Indirect effects in predator-prey interaction: development and predation rates by immature Neoseiulus cucumeris increased by odour from its prey (Tyrophagus putrescentiae)

2020 ◽  
Vol 25 (7) ◽  
pp. 1247-1256
Author(s):  
Xin-yao Gu ◽  
Guang-yun Li ◽  
Zhi-qiang Zhang
Keyword(s):  
Indirect Effects ◽  
Survival Rates ◽  
Predatory Mites ◽  
Tyrophagus Putrescentiae ◽  
Neoseiulus Cucumeris ◽  
Predator Prey ◽  
Factitious Prey ◽  
Consumption Rates ◽  
Prey Interaction ◽  
Predation Rates

Predator-prey interactions have long been of great interest to ecologists. Although the direct consumptive effects have received extensive research, indirect influences of odour derived from their conspecifics and prey on predators have largely been underestimated and overlooked. In this study, the indirect effects of predator-prey interactions were determined with predatory mites Neoseiulus cucumeris and its factitious prey Tyrophagus putrescentiae. The responses of immature N. cucumeris to mixed odour with their conspecifics and prey were determined in a laboratory experiment. Our results showed that the mixed odour with their conspecifics did not demonstrate any obvious influences on the survival rates, developmental periods, predation rates and activities of the predatory mites. Intriguingly, the predators prolonged their protonymphal stage and consumed more prey eggs when exposed to mixed odour with their prey. Our results indicated that the mixed odour with their conspecifics was weak and its influence was insignificant for this species, but the prey odour showed a signifcant influence on the growth and consumption rates of immature predators, which highlighted that the indirect influences of predator-prey interactions on the predator were substantial and cannot be neglected.

scholarly journals Assessing multiple predator, diurnal and search area effects on predatory impacts by ephemeral wetland specialist copepods

2019 ◽  
Vol 54 (1) ◽  
pp. 181-191 ◽  
Author(s):  
Ross N. Cuthbert ◽  
Tatenda Dalu ◽  
Ryan J. Wasserman ◽  
Cristián J. Monaco ◽  
Amanda Callaghan ◽  
...  
Keyword(s):  
Surface Area ◽  
Population Level ◽  
Time Of Day ◽  
Habitat Characteristics ◽  
Physical Habitat ◽  
Trophic Groups ◽  
Ephemeral Wetland ◽  
Consumption Rates ◽  
Prey Interaction ◽  
Predation Rates

AbstractPredator–prey interaction strengths can be highly context-dependent. In particular, multiple predator effects (MPEs), variations in predator sex and physical habitat characteristics may affect prey consumption rates and thus the persistence of lower trophic groups. Ephemeral wetlands are transient ecosystems in which predatory copepods can be numerically dominant. We examine the interaction strengths of a specialist copepod Paradiaptomus lamellatus towards mosquito prey in the presence of conspecifics using a functional response approach. Further, we examine sex variability in predation rates of P. lamellatus under circadian and surface area variations. Then, we assess the influence of a co-occurring heterospecific predatory copepod, Lovenula raynerae, on total predation rates. We demonstrate MPEs on consumption, with antagonism between conspecific P. lamellatus predatory units evident, irrespective of prey density. Furthermore, we show differences between sexes in interaction strengths, with female P. lamellatus significantly more voracious than males, irrespective of time of day and experimental arena surface area. Predation rates by P. lamellatus were significantly lower than the heterospecific calanoid copepod L. raynerae, whilst heterospecific copepod groups exhibited the greatest predatory impact. Our results provide insights into the predation dynamics by specialist copepods, wherein species density, diversity and sex affect interaction strengths. In turn, this may influence population-level persistence of lower trophic groups under shifting copepod predator composition.

Functional response analysis of size-selective predation by the notonectid predator Anisops deanei (Brooks) on Daphnia thomsoni (Sars)

1984 ◽  
Vol 35 (6) ◽  
pp. 725 ◽  
Author(s):  
JG Reynolds ◽  
MC Geddes
Keyword(s):  
Functional Response ◽  
Prey Type ◽  
Size Class ◽  
Response Analysis ◽  
Response Curves ◽  
Selective Predation ◽  
Size Classes ◽  
Effective Predator ◽  
Typical Type ◽  
Predation Rates

The functional response of A. deanei to uncrested D. thomsoni was calculated by predation experiments in the laboratory. A. deanei produced typical type 11 functional response curves when presented with increasing densities of any given size-class of D. thomsoni Predation rates were highest for small size-classes and decreased for prey sizes above 2 mm In mixed-prey populations A deanet showed a greater preference towards the smaller, preferred prey than was predicted from the angle-prey-type expenments, thus demonstrating an exercise of choice by the predator. Crests developed by the smaller, preferred size-classes of D. thomsoni did not act as effective anti-predator mechanisms against A. deanei which may be able to remam an effective predator on crested populations of D. thomsonl.

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.

Cereal Consumption, Production, and Prices in West Pakistan (Notes & Comments)

1968 ◽  
Vol 8 (2) ◽  
pp. 288-306 ◽  
Author(s):  
G. C. Hufbauer
Keyword(s):  
Food Consumption ◽  
Ad Hoc ◽  
Dry Weight ◽  
Small Sample ◽  
Tax Rates ◽  
Active Population ◽  
Early Settlement ◽  
Consumption Rates ◽  
Late Nineteenth ◽  
Better Than

In the late nineteenth and early twentieth centuries, several Punjab Settlement Officers attempted to estimate food consumption rates. These estimates, based on direct observation and ad hoc guesses, were made partly out of academic curiosity, but more urgently, as an aid in establishing the land revenue (i.e., tax) rates. The pre-1926 estimates are summarized in Table I, expressed in pounds of wheat and other foodgrain consumption per person per year1. Broadly speaking, the later, more systemtic observers (e.g., Sir Ganga Ram and C. B. Barry), found lower consumption levels than the earlier observers. It was generally accepted that the rural populace ate better than urban dwellers. Despite the ingenuity of the early Settlement Officers, their compiled estimates suffer from all the difficulties of haphazard small sample observation. Given the revenue purpose of the estimates, they may be biased towards the able-bodied, economically active, population. Further, the very early estimates may have confused dry weight with cooked weight, including water.

KOMPOSISI JENIS DAN KELIMPAHAN IKAN DI PERAIRAN TELUK DORERI, MANOKWARI

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Maria Massora
Keyword(s):  
Fish Species ◽  
Economic Value ◽  
High Abundance ◽  
Abundance Index

<em>A study was done to search the composition and abundance of fish species in the waters of the Doreri Gulf the District of Manokwari, from September - October 2005.  The fish catchments wash about 143 specimens consist of 49 species included in 23 families.  The species of fish with a high abundance index consists of Nemipterus celebicus, Upeneus sundaicus, and Upeneus sulphureus.  Those fishes have a high economic value in the market of Manokwari</em>

Effects of Predation and Trophic Conditions on the Reproduction of Tylototriton verrucosus (Caudata: Salamandridae) in Darjeeling

2011 ◽  
Vol 4 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Ritwik Dasgupta
Keyword(s):  
Frequency Distribution ◽  
Primary Productivity ◽  
Egg Size ◽  
Zooplankton Abundance ◽  
Trophic Conditions ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
High Predation ◽  
Hatchling Size ◽  
Predation Rates

The facts that small hatchlings emerged from small eggs laid under high predation levels prevailing at the lower altitudes of distribution of this species in Darjeeling while larger hatchlings emerged from larger eggs laid under lower levels of predation at higher altitudes, show that predation is not selected for large egg and initial hatchling size in this salamandrid species. Metamorphic size was small under high predation rates because this species relied on crypsis for evading predators. Egg and hatchling size are related inversely to levels of primary productivity and zooplankton abundance in lentic habitats. Hatchling sizes are related positively to egg size and size frequency distribution of zooplankton. Small egg and small hatchling size have been selected for at the lower altitudes of distribution of this salamandrid in Darjeeling because predation rates increased in step with improvement in trophic conditions at the lower altitudes.

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