In this study, several experiments were performed to determine the effects of cell toxin concentration, composition and toxicity of Alexandrium minutum on ingestion rate, egg production, hatching success and naupliar fitness of the copepod Acartia clausi. A combined of A. minutum and nontoxic algae (Tetraselmis suecica, Isochrysis galbana and Prorocentrum micans) was used as food. The strain of A. minutum used in this study (A1 1V) only contains gonyautoxins. Copepods ingested a higher amount of A. minutum cells as the concentration of toxic dinoflagellates increased, and in response to decreasing total food concentration available for the copepods. A positive relationship was obtained between A. minutum cells ingested by copepods and total toxin concentration per copepod. Only gonyautoxins were detected in the copepods. Egg production, hatching success and naupliar production were lower as copepods ingested a higher amount of toxic dinoflagellates. The negative effect of A. minutum on copepods was higher as A. minutum had a higher cell concentration of GTX1. Finally, the results obtained from nauplii incubated with T. suecica and I. galbana showed that, nauplii hatched from females fed nontoxic food (T. suecica and I. galbana ) reached copepodite stage earlier, than those nauplii hatched from females fed with a combined of toxic (A. minutum ) and nontoxic food (T. suecica and I. galbana).