The influence of autotrophic and heterotrophic foods on the demography of Daphnia longispina under starved, semi-natural and enriched conditions
V. Picard, N. Lair-2000
Journal of Plankton Research, 22 (10) : 1925-1944
(from Current Contents)
Abstract :
We tested the influence of different types of food on
the fitness of Daphnia longispina during a period of poor resources by
comparing the growth and reproduction of individuals fed on different diets.
When Daphnia were under starvation conditions, both dissolved organic carbon
and metabolic products enhanced bacterial growth, and the cladoceran
produced 15 neonates and survived for the 55 days of experiment. In the
natural water, the edible food consisted essentially of bacteria and
heterotrophic flagellates, which enabled the cladoceran to grow and
reproduce. In water enriched with Cryptomonas (an alga) or Chilomonas (a
heterotrophic flagellate), the daphnid growth rates increased considerably
from generation to generation, but later in the time course of the
experiment with Chilomonas than with Cryptomonas. This alga enhanced the
phosphorus:carbon ratio. The primiparous daphnids fed with Cryptomonas were
smaller than those fed with the heterotrophic flagellate and enrichment with
the heterotrophic flagellate also enhanced reproduction. In Lake Tazenat,
when the algal biomass was insufficient to support the Daphnia life cycle,
the heterotrophic organisms were an essential food source. When feeding
essentially on bacteria, Daphnia has the capacity to grow and reproduce at
very low food concentrations, and this is important in determining its
fitness under competitive conditions.
(Univ Blaise Pascal, CNRS, 4 Rue Ledru, F-63057
Clermont Ferrand, France)