Miguel F.Acevedo
ABSTRACTS
MODELING CLADOCERAN POPULATION RESPONSES TO STRESS WITH PARTICULAR
REFERENCE
TO SEXUAL REPRODUCTION
Non Linear World. 2:97-129. 1995
M.F.Acevedo 1,2,5; Waller W.T. 1,3; Smith D.P. 1,3; Poage D.W.4; and
McIntyre
P.B. 1
1 .-Institute of Applied Sciences, 2.- Department of Geography, 3.-
Department
of Biology University of North Texas, Denton, TX 76203. 4.- Eli Lilly
and
Company, Greenfield, IN 46140. 5.- Universidad de Los Andes, Merida,
Venezuela
Abstract
This paper describes a model of the population-level consequences of
the
effects of physical and chemical stressors on the reproduction,
mortality
and growth of cladocerans. Ceriodaphnia dubia is selected for
this
effort due to its extensive use in toxicity testing. The model is based
on the dynamics of the life cycle and includes net rates of
reproduction,
hatching, maturation and mortality. The density of neonates and mature
individuals, males and females, as well as of sexual eggs are
calculated
as a function of these rates. The model includes the consequences of
reducing
growth rates, decreasing fertility rates, increasing mortality rates
and
switching to sexual reproduction conditioned by changes of ingestion
rate,
which in turn depends on physical conditions, temperature and
photoperiod,
chemical stress, and food quantity and/or quality. Three indices are
used
to infer the population- level consequences of these stresses: number
of
sexual eggs at the end of the season, maximum number of neonates and
maximum
number of adults during the season. This model contributes to
understanding
populations under stress, and may aid in conducting risk assessments.
Key words: Cladocera, Daphnia, Ceriodaphnia, sexual reproduction,
stress,
epphipia, population.
AMS subject classification: 92D25, 34A34.
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