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  • life history  (2)
  • biomass  (1)
  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 11 (1997), S. 439-450 
    ISSN: 1573-8477
    Keywords: food ; life history ; predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Variation in offspring size and number has been described for a wide range of organisms. Many theoretical models predict that in a given environment, the production of one single offspring size would yield the highest parental fitness. In most planktonic cladocerans, however, offspring size has been found to increase with size and age of the mother, and as individuals of variable size often co-occur within a population, offspring of variable sizes can be produced simultaneously. In this study, I investigated the relationship between age of the mother and size of her offspring to assess at what age of the mother the optimal offspring size was produced. Optimal offspring size was defined as that size of the offspring yielding the highest parental fitness, which translates to a definition of optimal offspring size as the one having the highest juvenile fitness per unit effort put in these juveniles. I observed that the youngest females produced offspring with the highest juvenile fitness per unit effort, and hence concluded that offspring produced by these females were of optimal size. Larger offspring produced by older females were estimated to yield only 70% of the potential fitness of optimally sized offspring.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 307 (1995), S. 109-115 
    ISSN: 1573-5117
    Keywords: Daphnia ; food quality ; life history ; standard carbon content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper we describe the life history consequences of feeding Daphnia galeata with different food types in different concentrations. We fed the animals with four concentrations of two green algae Scenedesmus obliquus and Chlamydomonas globosa, given separately as well as in a 1:1 mixture. Growth, reproduction and condition of the animals and consequently the intrinsic rate of population increase, r, increased with the concentration of the food for all three experimental series. The life history parameters measured were lowest in the animals raised on C. globosa. Animals fed on S. obliquus showed higher values for r. We observed a distinct synergistic effect of the two algal species: growth, reproduction, condition and r were significantly higher for the animals raised on the mixed media as compared to the animals raised on the mono-algal media. We conclude that the two algal species represented complementary food resources.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5117
    Keywords: microcrustacean zooplankton ; tropical limnology ; biomass ; production ; empirical relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Production, biomass and productivity of the microcrustacean zooplanktonpopulations of three low-land reservoirs, Tissawewa (eutrophic), Ridiyagama(moderately eutrophic), and Muruthawela (mesotrophic) in South-east SriLanka were studied. The temporal variation of zooplankton production wasstudied in Tissawewa on basis of fortnightly sampling on five fixed samplingstations for 2 years. Zooplankton production was relatively high, mainlybecause of high copepod production predominantly realised due to twocalanoid copepods, Phyllodiaptomus annae and Heliodiaptomus viduus. Abouthalf of the copepod production was contributed by the naupliar instarstages, whereas the contribution of the eggs was generally much smaller(〈20%). In contrast, the cladoceran production consisted for ca50–70% of egg production. The results of this study werecompared with those from more than twenty other tropical and subtropicalwaterbodies reported in the literature by deriving empirical relationshipsbetween mean phytoplankton biomass and mean zooplankton biomass andproduction. Mean zooplankton biomass and annual zooplankton production werefound to be positively related to mean phytoplankton biomass, and meanphytoplankton biomass proved to be a good predictor of mean zooplanktonbiomass (r2 = 0.58) and a moderate good predictor ofannual zooplankton production (r2 = 0.43). However,the relationships between the mean phytoplankton biomass and zooplankton P/Bwere not significant neither for small-bodied and large-bodied cladoceransnor for copepods.
    Type of Medium: Electronic Resource
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