Development of new combined method based on reading of ovarian tracheoles and the observation of follicular dilatations for determining the physiological age of Anopheles gambiae s.s.

The conventional dilaceration of ovaries is binding at the beginning of ovary development. However, reading ovarian tracheoles was very easy in stage I-II mean. The combination of both methods can really reduce the number of age indeterminations recorded with the two methods separately. The present study aimed to identify a method capable of determining physiological age of mosquitoes regardless of their ovarian development stage. In the present study, mosquitoes were caught in houses using window traps. After identification of Anopheles gambiae s.l species, their ovaries were dissected in distilled water. An ovary was left in distilled water for tracheoles reading and the other in a physiological liquid to search for follicular dilatation after dilaceration of ovary. The other body parts of mosquitoes were used to identify the species of the A. gambiae complex by polymerase chain reaction. The ovarian tracheoles reading method was unable to determine physiological age of 25% (n=28) of 112 A. gambiae s.s. analyzed. With follicular dilations observation method, the physiological age of 16.96% (n=19) mosquitoes was not determined; but, the age indetermination rates were reduced to 0.89% by combining the two methods. The combination of ovarian tracheoles reading method and follicular dilatation observation method significantly reduced (almost null) the number of physiological age indeterminations recorded using the two methods separately.