An experimental test of the egg‐ratio method with instantaneous birth rate as an independent variable

Bennett, William N.; Boraas, Martin E.

doi:10.4319/lo.1989.34.6.1120

Cited by 12 publications

(4 citation statements)

References 11 publications

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“…This assumes a constant mortality rate over all life stages including eggs. In a comparison of calculated and observed birth rates with steady state cultures of B. calyciflorus, Paloheimo's equation showed the best fit to the calculated data (Bennett & Boraas, 1989) . Introducing Paloheimo's b in Lotka's equation r=b-m (Lotka, 1922), where m is mortality rate, and plotting r versus In (ER + 1), the inverse slope of a linear regression gives DE and the intercept gives the mortality rate (Rothhaupt, 1990) .…”

Section: Experimental Designmentioning

confidence: 89%

Influence of the filamentous cyanobacterium Planktothrix agardhii on population growth and reproductive pattern of the rotifer Brachionus calyciflorus

Weithoff

Walz

1995

Hydrobiologia

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The population dynamics of B . calyciflorus was investigated using a green alga, Monoraphidium minutum, and a blue-green alga Planktothrix agardhii as food sources, separately and as mixtures . Growth rate (r), egg ratio (ER), and juvenile development time (DJ) were measured in the laboratory and mortality rate and embryonic development time (DE) were calculated . With M. minutum, Brachionus showed a typical growth curve ('Monodkinetics') dependent on food concentration . In contrast B. calyciflorus did not grow well on P. agardhii. With all food concentrations the measured growth rates were about r=0 . At low food concentrations r was low with both food types, but the ER of B. calycilorus was significantly higher with P. agardhii as food source. Furthermore the relative egg volume of females carrying one egg was higher with Planktothrix than with Monoraphidium.An addition of P. agardhii to M. minutum led to increasing growth rates . Highest growth rates were found with complementary food sources . High food concentrations of M. minutum shortened the juvenile development (DJ) time, but D J was uneffected by different P. agardhii food concentrations . A mixture of both algae did not shorten D j compared with M. minutum as single food . The calculated DE was not effected by different food qualities but the calculated mortality was nearly 3 times higher with P agardhii as food .

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Section: Experimental Designmentioning

confidence: 89%

Influence of the filamentous cyanobacterium Planktothrix agardhii on population growth and reproductive pattern of the rotifer Brachionus calyciflorus

Weithoff

Walz

1995

Hydrobiologia

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“…Bennet & Present et ai, 1987Boraas, 1989 Choice of model Non-steady-state dynamic Selective predation Sampling error Accurate estimate of D Emigration and immigration Hatching of resting eggs compared to death-rate estimates obtained using various birth-rate models. The design employed allowed for an assessment of selective predation, deviations from steady-state dynamics, and sampling error in non-patchy populations on model accuracy.…”

Section: Gabrielmentioning

confidence: 99%

“…The directly determined death rates were Table 1 The various sources of error, when estimating birth rates of zooplankton ptipulations in the field, accounted for in those studies which have directly measured demographic rates and compared these rates to rates estimated using the egg-ratio method. An X means the source of error was included in the experiment design Source of error Gabriel Bennet & Present et ai, 1987Boraas, 1989 Choice of model Non-steady-state dynamic Selective predation Sampling error Accurate estimate of D Emigration and immigration Hatching of resting eggs compared to death-rate estimates obtained using various birth-rate models. The design employed allowed for an assessment of selective predation, deviations from steady-state dynamics, and sampling error in non-patchy populations on model accuracy.…”

Section: Introductionmentioning

confidence: 99%

An experimental test of the egg‐ratio method: estimated versus observed death rates

1992

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1. The accuracy of death-rate estimates provided by the egg-ratio method was assessed by directly measuring the real death rates of six large laboratory Daphnia populations for 40 days.2. Of six models tested the Kawecki iterative model gave the best relationship to real death rates in terms of variance explained, bias, and fit at both 4-and 8-day sampling intervals. Although considered theoretically correct by persons familiar with the mathematics of egg-ratio models, the Edmondson-Paloheimo model gave slightly worse results in terms of bias and fit. 3. Using raw data, as opposed to smoothed data, gave the best fit between estimated and observed rates for both the Kawecki iterative and Edmondson-Paloheimo models. 4. Size-selective predation did not increase error in estimates of the death rate; however, non-steady-state dynamics were correlated with error in model estimates. 5. In general, the models gave a relatively good description of real dynamics, but they* regularly produced negative death rates, and were grossly wrong for some individual estimates. The present study also gives practical suggestions on application of this technique to field populations.

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“…This, coupled with mathematical modelling and computer simulations, have greatly improved the applicability of ER for estimating population growth rates (Keen & Nassar, 1981;Bennett & Boraas, 1989;Devetter & SedÕa, 2003). Population growth rate experiments in the laboratory are simplified and allow separate measurement of both the natality and mortality rates.…”

Section: Introductionmentioning

confidence: 99%

Factors Affecting Egg-ratio in Planktonic Rotifers

2005

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EdmondsonÕs egg ratio (number of amictic eggs per female) is an important life history variable, which has been in wide use to understand and predict patterns of population growth in planktonic rotifers under field conditions. It is also useful as an indicator of the health of rotifers under culture conditions. Generally, an inverse relationship exists between the egg ratio and the density of females in a population. A number of abiotic and biotic factors influence the egg ratio. For example, temperature can cause marked changes in the egg ratio by influencing the frequency of egg production and the hatching times of parthenogenetic eggs. Also, preferential feeding on ovigerous females of rotifers by invertebrate predators such as Asplanchna will lower the egg ratios of the population. The easy detachment of eggs, as may be the case in some members of the Brachionidae especially during enhanced reproduction when food levels are high, may also cause an underestimation of the egg ratio. In this review, we discuss the egg ratio of selected rotifer species in relation to the role of diel changes in egg production, the frequency or the intensity of feeding, the problems of distinguishing between different egg types and the negative effect of stressors such as toxicants and diet quality.

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An experimental test of the egg‐ratio method with instantaneous birth rate as an independent variable

Cited by 12 publications

References 11 publications

Influence of the filamentous cyanobacterium Planktothrix agardhii on population growth and reproductive pattern of the rotifer Brachionus calyciflorus

Influence of the filamentous cyanobacterium Planktothrix agardhii on population growth and reproductive pattern of the rotifer Brachionus calyciflorus

An experimental test of the egg‐ratio method: estimated versus observed death rates

Factors Affecting Egg-ratio in Planktonic Rotifers

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