Bi-autogenous ovarian cycles in Egyptian aedes caspius pallas [Diptera: culicidae]

ABSTRACT

Autogenous Aedes [Ochlerotatus] caspins Pallas from Aswan deposits 1 to 2 egg batches without a blood meal. Repeated ovarian developmental cycles were responsible for the bi-ovipositional pattern as indicated by the presence of 2 dilatations in the ovariolar pedicel of bi-autogenous females and by the early stages of development of the ovaries [II and II B] observed 1-3 days following initial oviposition, later stages of maturation occurred progressively. Three levels of autogeny were distinguished within the population mono-autogenous females that deposited 1 egg batch and were unable to initiate further oogenesis [54.4%], mono-autogenous females in which various degrees of vitellogenesis developed posterior to initial sole oviposition [40%] and bi-autogenous females [5.6%] that deposited 2 autogenous egg batches but were unable to develop any further oogenesis. The fecundity of mono-autogenous females [about 56 eggs] whether they could develop a 2nd autogenous cycle or not, was comparable to that of bi-autogenous mosquitoes in their initial egg batch [53 eggs], suggesting that ability to develop a subsequent autogenous follicular cycle is determined by factors independant of nutrient reserves accumulated during the larval stage. The 2nd egg batch of bi-autogenous females was smaller [21 eggs] than the initial batch. The total reproductive effort of bi-autogenous individuals [about 74 eggs] was superior to that of mono-autogenous females. However, bi-autogenous females laid the totality of their eggs within about 16 days, whereas the average initial gonotrophic cycle of mono-autogenous females was 6 days. It is concluded that bi-autogeny in Ae. caspius would be of little value in the population increase although it may contribute maintaining the species when the host is not available