Life table
demography and population growth of Daphnia laevis (Cladocera, Anomopoda)
under different densities of Chlorella vulgaris and Microcystis aeruginosa
S. Nandini, S.S.S. Sarma,
P. Ramirez-Garcia-2000
Crustaceana, 73
Part 10 : 1273-1286 (from
Current Contents)
Abstract:
The authors studied the life table demography and
population growth of Daphnia laevis using the green alga Chlorella vulgaris
and the cyanobacterium Microcystis aeruginosa (offered in colonial form)
under two food concentrations (1 x 10(6) and 3 x 10(6) cells ml(-1)). The
experimental design consisted of two types of food, and of two
concentrations of algae, each with three replicates. The design was the same
for both the life table study and the study of population growth. The
variables derived were: age specific survivorship, age-specific
reproduction, average lifespan, age-specific life expectancy, gross
reproductive rate, net reproductive rate, generation time, reproductive
effort, stable age distribution, and rate of population growth derived
iteratively. While survivorship variables were not affected significantly
either by the type of food or by the concentration offered, reproductive
variables of D. laevis were significantly influenced by the type of alga
rather by than its density. Cladocerans fed Chlorella reached maximal
population abundance earlier than those fed Microcystis. Throughout the
population growth study, peak population abundance values of D. laevis
varied from 0.34 to 0.49 ind. ml(-1). There was no significant difference in
the peak population density reached with respect to food type or food
concentration. The rate of population growth per day varied from 0.1 to
0.15. Our study indicates that D. laevis can successfully utilize a
basically toxic strain of M. aeruginosa, with which it co-exists in a
man-made reservoir in Mexico.
(Natl Autonomous Univ Mexico, CyMA Project, Campus
Iztacala, Av Los Barrios S-N, AP 314, Tlalnepantla 54090, Los Reyes, Mexico,
e-mail : nandini@servidor.unam.mx)