Taai Kritsana, Harbach Ralph E, Aupalee Kittipat, Srisuka Wichai, Yasanga Thippawan, Otsuka Yasushi, Saeung Atiporn
Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand.
Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK.
Parasit Vectors. 2017 Feb 21;10(1):97. doi: 10.1186/s13071-017-2035-6.
Species of the Anopheles minimus complex are considered to be the primary vectors of malaria in South and Southeast Asia. Two species of the complex, Anopheles minimus and Anopheles harrisoni, occur in Thailand. They are sympatric and difficult to accurately distinguish based on morphological characters. The aim of this study was to investigate the potential of antennal sensory organs to distinguish these two species. Additionally, we investigated their ability to mate in cages of different sizes, as well as the possible mechanism(s) that evokes stenogamous behavior.
Large sensilla coeloconica present on the antennae of females of An. minimus and An. harrisoni were counted under a conventional light microscope and various types of antennal sensilla were examined under a scanning electron microscope (SEM). Determinations of mating ability were carried out in 20 and 30 cm cages with a density resting surface (DRS) of 7.2. The insemination rate, frequency of clasper (gonocoxopodite) movement of the male genitalia during induced copulation and duration of mating of the two species were compared.
The mean numbers of large sensilla coeloconica on antennal flagellomeres 1-8 and the mean number of large sensilla coeloconica on each flagellum in An. minimus (26.25) and An. harrisoni (31.98) were significantly different. Females of both species bear five types of antennal sensilla: chaetica, trichodea, basiconica, coeloconica and ampullacea. Marked differences in the structure of the large sensilla coeloconica were observed between the two species. Furthermore, only An. minimus could copulate naturally in the small cages. The frequency of clasper movement in the stenogamous An. minimus was significantly higher than in An. harrisoni, but there was no difference in the duration of mating.
To our knowledge, this study is the first to examine and discover the usefulness of large sensilla coeloconica on the antennae of females and the frequency of clasper movement in males for distinguishing the sibling species An. minimus and An. harrisoni. The discovery provides an effective and relatively inexpensive method for their identification. Additionally, the greater frequency of clasper movement of An. minimus might influence its ability to mate in small spaces.
微小按蚊复合体的物种被认为是南亚和东南亚疟疾的主要传播媒介。该复合体的两个物种，即微小按蚊和哈氏按蚊，在泰国存在。它们同域分布，基于形态特征难以准确区分。本研究的目的是调查触角感觉器官区分这两个物种的潜力。此外，我们研究了它们在不同大小笼子中的交配能力，以及引发狭域交配行为的可能机制。
在传统光学显微镜下对微小按蚊和哈氏按蚊雌蚊触角上的大型腔锥感器进行计数，并在扫描电子显微镜（SEM）下检查各种类型的触角感器。在密度静止表面（DRS）为7.2的20厘米和30厘米笼子中进行交配能力测定。比较了两种按蚊的受精率、诱导交配期间雄性生殖器抱握器（gonocoxopodite）运动频率和交配持续时间。
微小按蚊触角鞭节1 - 8上大型腔锥感器的平均数量以及每根触角上大型腔锥感器的平均数量（26.25）与哈氏按蚊（31.98）有显著差异。两种按蚊的雌蚊都有五种类型的触角感器：刺形感器、毛形感器、锥形感器、腔锥感器和瓶形感器。在两种按蚊之间观察到大型腔锥感器结构上的明显差异。此外，只有微小按蚊能够在小笼子中自然交配。狭域交配的微小按蚊抱握器运动频率显著高于哈氏按蚊，但交配持续时间没有差异。
据我们所知，本研究首次检查并发现雌蚊触角上的大型腔锥感器以及雄蚊抱握器运动频率对于区分近缘物种微小按蚊和哈氏按蚊的有用性。这一发现为它们的鉴定提供了一种有效且相对廉价的方法。此外，微小按蚊抱握器运动频率更高可能影响其在小空间中的交配能力。
