[Sequence analysis of ribosomal DNA internal transcribed spacer 2 of sympatric populations of Anopheles sinensis of different feeding preferences].

Objective: To investigate the existence of genetic divergence of sympatric populations of Anopheles sinensis of different feeding preferences based on the rDNA-ITS2 sequence differences.

Methods: A large number of wild anopheles populations were trapped all night by man-baited net and calf-baited net that had been set up between high-density natural villages of An. sinensis populations and vector-breeding sites, from which two groups of An. sinensis were separated by morphological identification and brought back to the lab for conventional breeding. A large closed greenhouse which temperature and humidity was appropriate was selected as research settings of mark-release-recapture methods by female mosquitoes, in the center of which above An. sinensis populations baited by man and calf and respectively correspondingly marked by red and yellow phosphors were released in together, in each side of which An. sinensis were recaptured simultaneously by man-baited net and calf-baited net. An. sinensis populations trapped by man twice were brought back to the lab and bred with man-blood, correspondingly ones trapped by calf with calf-blood. Man-preferring and calf-preferring strains were screened respectively from An. sinensis which had been baited by man and calf by the mark-release-recapture methods after parent and F1 mosquitoes, and sequencing and aligning of both rDNA-ITS2 were conducted via PCR amplification.

Results: The recapture ratios of wild parental mosquitoes An. sinensis of man-preferring group by man-baited net and calf-baited net were 54.07% (339/627) and 45.93% (288/627) respectively, and ones of calf-preferring group by man-baited net and calf-baited net were 58.01% (409/705) and 41.99% (296/ 705) respectively. Two groups of parental mosquitoes trended towards selecting the original blood hosts in host-seeking preference (Χ2 = 19.42, P < 0.01). The recapture ratios of F1 mosquitoes An. sinensis of man-preferring group by man-baited net and calf-baited net were 63.43% (765/1 206) and 36.57% (441/1 206), and ones of calf-preferring group by man-baited net and calf-baited net were 68.22% (1 039/1 523) and 31.78% (484/1 523). Two groups of F1 mosquitoes had more significant characteristics of selecting the original blood hosts in host-seeking preference (Χ2 = 271.69, P < 0.01) and showed the genetic differentiation phenomenon, but the results of sequencing and aligning of the rDNA-ITS2 via PCR amplification showed no difference in base sequence between the two strains and both were 469 bp.

Conclusions: The genetic divergence based on the rDNA-ITS2 sequence does not happen in An. sinensis sympatric populations of different feeding preferences.