Hydrocarbons Depress Growth and Reproduction of Daphnia pulex (Cladocera)

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Abstract
Daphnia pulex were acutely and chronically exposed to water-soluble fractions of hydrocarbons. In acute studies, the most-to-least toxic were coal-tar creosote, No. 2 fuel oil, naphthalene, and phenanthrene. During chronic studies, Daphnia were monitored for molting frequency, growth rates, production of total and live young, number of nonviable eggs, partial and full abortions, and whether or not abortions occurred prior to completion of embryonic development. For creosote and phenanthrene, marked reduction occurred in growth rates, number of broods, and impairment of molting, and an increase occurred in abortion rates. No. 2 fuel oil produced similar effects, but results were less significant. Naphthalene only produced a slight reduction in growth rate at the concentrations studied. It is hypothesized that the effect on growth and reproduction may be due to PAH-induced disturbance on some aspect of metabolic control of reproduction and molting.Key words: phenanthrene, naphthalene, creosote, No. 2 fuel oil, Daphnia, toxicity