Duration of the Aquatic Stages of Povilla adusta Navás (Ephemeroptera: Polymitarcidae)

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Abstract
The duration of the aquatic stages of the mayfly, Povilla adusta Navás, in Lake Victoria, Uganda, has been determined by analysing larval samples from the stomachs of an insectivorous fish, Mormyrus kannume Forsk., and by culturing eggs in vitro. Emergence shows a well-defined lunar rhythm and, since adults live for only about one hour, duration of the aquatic stages must be an integral number of lunar months. Results indicate that a generation is usually completed in four or five months. Approximately the first two weeks of this period are spent in the egg.The periodicity of reproduction imposes a feeding rhythm on certain species of fish in Lake Victoria. Some biological implications of the need for synchronisation are briefly discussed.