Demography and population growth of Asplanchna girodi (Rotifera) as a function of prey (Anuraeopsis fissa) density

Abstract

Laboratory studies on population growth and life table demography of Asplanchna girodi were conducted at 25±1 °c using Anuraeopsis fissa as prey at four (250, 500, 1000 and 2000 ind ml -1 ) densities . A prey density of 100 ind ml -1 per predator per day did not support A . girodi, while at the highest prey concentration, A . girodi reached a peak of 115±7 ind ml -1 . The age distribution of A. girodi indicated that non-adults constituted about 2/3rd of the population at all prey concentrations . A decrease in prey availability resulted in increased mortality of non-adults . At the highest prey density, the rate of population increase (r) was 1 .51 d -1 . The significance of estimating mortality in population growth studies is discussed .Life table demography of A . girodi was also studied using the same prey at the same concentrations . None of the survivorship parameters (e .g . mean lifespan and mean survivorship) showed a significant relation to prey density . Net reproductive rate and generation time (but not rate of population increase) were affected by prey abundance .

Combined effects of temperature and prey (Brachionus angularis) density on life-table demography and population growth ofAsplanchna brightwelli(Rotifera)

“…The data of net reproductive rate of A. brightwelli obtained in the present study were much lower than those reported for Asplanchna (e.g., 9-15 offspring female x1 lifespan x1 for A. girodi; Dumont and Sarma, 1995), which might be attributed to the much lower prey biomass used here.…”

“…The intrinsic rate of population increase of A. girodi obtained from life-table demography increased with increasing prey (B. havanaensis or B. calyciflorus) availability in the medium , but that of A. girodi was not significantly affected by A. fissa density (Dumont and Sarma, 1995). Similarly, in the present study, at 16 and 20 xC, B. angularis density did not affect the intrinsic rate of population increase of A. brightwelli.…”

“…The survival of A. girodi De Guerne was not significantly affected by the density of both B. havanaensis Rousselet (densities ranged from 1 to 8 ind.mL x1 ) and Anuraeopsis fissa Gosse (250-2000 ind.mL x1 ), but the average lifespan of A. girodi fed B. calyciflorus Pallas at 1 ind.mL x1 was longer than that at 2-8 ind.mL x1 . The generation time of A. girodi decreased with increasing prey (B. havanaensis or B. calyciflorus) density, but increased with increasing A. fissa density (Dumont and Sarma, 1995;Sarma et al, 2003). In the present study, we found that the effect of prey density on survival and development of A. brightwelli also depended on temperature.…”

“…The net reproductive rate of A. girodi fed B. calyciflorus at 2 ind.mL x1 or B. havanaensis at 1 ind.mL x1 was the lowest , but that of A. girodi fed A. fissa increased with increasing prey density (Dumont and Sarma, 1995). In the present study, we found that the effect of prey density on the net reproductive rate of A. brightwelli depended on temperature.…”

“…Much literature is available on the food and feeding habits of Asplanchna, both from field and laboratory studies (reviewed in Dumont, 1977;Pourriot, 1977;Williamson, 1983;Arndt, 1993;Sarma, 1993;Conde-Porcuna and Sarma, 1995;Iyer and Rao, 1996;Nandini and Sarma, 1999;Nandini et al, 2003;Sarma et al, 2011). Although there are some data on the life-table demography and the population growth rate of Asplanchna as a function of prey levels (e.g., Urabe, 1992;Dumont and Sarma, 1995;Conde-Porcuna and Declerck, 1998;Sarma et al, 1998Sarma et al, , 2002aSarma et al, , 2003Sarma, 1999, 2000;Nandini et al, 2003), the combined effects of temperature and the prey level are inadequately studied (Verdone-Smith and Enesco, 1982).…”