Interaction between insect larvae and tadpoles in tropical rain pools

Abstract. 1. Ephemeral rain pools on rock surfaces are common in Africa and are inhabited by dense populations of aquatic dipteran larvae. About 30% of the pools also support large numbers of tadpoles of the frog Ptychadena anchietae .
2. Experiments reveal that the presence of tadpoles suppress eclosion of the rock pool dwelling midge Chironomus imicola .
3. However, the presence of tadpoles also shortens the larval life-span of C. imicola by speeding up growth rates. Since the larval stages must be completed before the pool dries tadpoles may help 'fine-tune' the dipteran to the rock pool habitat.
4. A change in the diet of Cimicola larvae is associated with the accelerated development. Grazing by tadpoles results in algae, growing on the water surface, reaching the mud in tadpole faeces. These algae represent a high protein and energy food not otherwise accessible to mud dwelling dipteran larvae.
5. When pools dry tadpoles are killed, but a second species of dipteran Dasyhelea thompsoni have larvae able to survive to dry phase in situ . These larvae are scavengers so that on reflooding dead tadpoles are available as food. Experiments show that the presence of tadpoles again increase larval growth rates.
6. Both alive and dead tadpoles therefore are responsible for increasing the quality and quantity of food available to dipteran larvae and are thus among the mechanisms ensuring an abundance of food for rock pool dwelling insect larvae.