Mating Biologyof Male Anopheles Arabiensis Patton (Diptera: Culicidae): Implications in The Use of Sterile Insect Technique in Vector Control

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Seidahmed, Osama Mohamed Elmekki
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The failure of control programs of mosquito borne diseases, including malaria, constitutes a major obstacle to the development of Sudan and other developing countries. This situation induced renewal of interest in the use of Sterile Insect Technique (SIT) in vector control. However, the potential role of SIT to eliminate malaria burden in developing countries is much challenged by the less available knowledge on biology of male malaria mosquito, particularly mating biology. This study was carried out both in the field and laboratory, during 2005-2006. It aimed to explore some issuess on mating biology of male Anopheles arabiensis that are pertinent to the fittness of the releases in a SIT project. In the laboratory, an optimal releasing age when males are physiologically able to mate, factors affecting male mating propensity and mating competitiveness between different age-categories were explored under laboratory conditions. Comparisons were made between two different colonies of An. arabiensis. In addition, effect of meal type on mating success was investigated. Intriguingly, a new male marking approach to study the mating competitiveness of male mosquito using fluorescent dyes was pioneered and experimentally designed. Mating and swarming behaviour of An. arabiensis were observed in the laboratory. Effect of swarm markers on mating success was investigated at the same settings. A fieldwork was accomplished in Dongola area, where a pilot project of SIT will take place. Observations on swarming behaviour of An. arabiensis were made. Characteristics of swarming statio ns at Dongola area were explored. Time of swarming start, five males, ten males, and maximum number of males joining the swarm, and ending of the swarm, over the swarming stations, were recorded. Moreover, susceptibility of the two sexes of An. arabiensis to four types of insecticides was tested in the area. Males were able to mate after they spent the first 24 hours after their emergence. Interestingly, a significant difference on insemination rate was obtained between the males of one-day-old and above age-groups of males both in the two colonies. Although doubling the number of males had no significant increase on mating success, a significant increase was recorded when the number was tripled. Elongating mating period to two, three and four nights had significantly augmented the mating success compared to a one night group. Feeding of males for five consecutive days on 10%Sucrose + 2%Methyl parbene, water, or 10%Date-palm juice had significantly reduced the mating success in comparison to 10%Sucrose. In the same way, feeding of one-day-old males on 10%Sucrose gave a significant higher insemination rate over the other feeding meals. In a consecutive series of experiments on fixed male-subjects, a decrease in insemination rate was observed in the 10%Sucrose+ 2%Methyl parbene group. Interestingly, a new marking method was developed to discriminate which type of males coupled with under-dissection females. While the males were topically treated with a fluorescent dye on their last abdominal segments, investigation for the marker was alternatively bounded to the females. By combining the male marking method with dissection of spermathecae, males of one day old were found uncompetitive to mate in comparison to 3 and 5 days old males. On the other hand, Males of 1One days old are uncompetitive to mate with the females in comparison to 5 and 8 days old ones. Three swarming stations were identified in a village 70km north of Dongola. Characteristics of the swarming stations were described. The earliest time to start swarming was observed at 18:32 evening. The maximum number of swarming males was shown at 18:58.30 + 00:04.30 at the first station; 19:02:30 + 00:12.30 at the second station; and at 19:06:30 + 00:01:30 at the third station. However, complete darkness had set on at 19:05 preventing observation of the end of swarming beyond this time. No ground marker was distinguished on any one of the three stations. On the other hand, no effect of swarm marker on mating success was earlier shown in the laboratory. It was also revealed that both sexes of males and females of An. arabiensis originated from the breeding site near the swarming stations are susceptible to Bendiocarb 0.1%, DDT 4%, Malathion 5% and Permethrin 0.75%. Implications of the above findings on mosquito SIT programs were discussed from a perspective to enhance the management of resources and to promote quality control of the mosquito pilot project in Northern State-Sudan
Mating Biology, Male Anopheles,Arabiensis,Patton,Sterile Insect Technique,Vector Control