Effet du phytoplancton Scenedesmus quadricauda (Meyen, 1929) sur les larves de Anopheles gambiae (Giles, 1902) en présence de leur aliment de référence

Abstract

The present study was initiated to understand the effect of the phytoplankton Scenedesmus quadricauda on Anopheles gambiae larvae in the presenc e of other food sources. An. gambiae larvae were exposed to S. quadricauda alone, to cat food
alone and to a mixture of the two foods. The gut contents of the larvae were observed microscopically immediately after feeding to determine the type of food inge sted by the larvae. Feed digestibility was determined by observing the condition
of the larval gut after dissection of the larvae every hour until 8 hours after exposure of the larvae to the feed. In parallel, b ioassays were performed with the same design and the mortality rates of An. gambiae larvae were determinate . The results showed that An. gambiae larvae ingested both phytoplankton and cat food in the presence of these two foods. When the larvae consumed the cat food, this food disappeared from the la rvae's intestine 5 hours after exposure. In contrast, the larvae's gut content changed very little when they consumed the phytoplankton S. quadricauda , which was observed in the larvae's gut throughout the experiment. Larval mortality rates were 0%, 100% a nd 85% when the larvae were exposed to cat food alone, S
quadricauda alone and to a mixture of this phytoplankton and cat food, respectively.
From the present study, it appears that , even if in presence of their reference food, An. gambiae consumed S. qua dricauda phytoplankton, were unable to digest it and died After trial in natural conditions, S. quadricauda could therefore be associated
with current malaria vector control tools.