Charalambous M, Ready P D, Shelley A J, Arzube M, Lowry C A
Department of Entomology, Natural History Museum, London, U.K.
Mem Inst Oswaldo Cruz. 1993 Jan-Mar;88(1):39-48. doi: 10.1590/s0074-02761993000100008.
Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotype and assess its degree of genetic separation from the Bucay cytotype. Both cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by possessing a differentiated X chromosome, which is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been established, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or most adult females of any one (cytotypepure) collection.
微小蚋在厄瓜多尔存在四种细胞型，该形态物种是盘尾丝虫病的主要传播媒介。在本文中，我们首次全面描述了克韦多细胞型幼虫多线染色体的带型，并评估了其与布卡伊细胞型的遗传分离程度。这两种细胞型与（卡亚帕细胞型的）染色体标准序列的差异在于固定倒位IIL - 5和IIL - 6。克韦多细胞型与标准细胞型和布卡伊细胞型的不同之处还在于其拥有一条分化的X染色体，这由倒位IIS - A表明。由于布卡伊细胞型和克韦多细胞型之间的生殖隔离程度尚未确定，它们必须被视为同一物种的种内变体。事实上，同工酶特征表明，布卡伊细胞型和克韦多细胞型的分化程度仅达到初始物种或地理种群预期的程度。此外，先前赋予布卡伊细胞型的姐妹种地位需要重新评估，因为在厄瓜多尔布卡伊与标准卡亚帕细胞型同域分布的地区缺乏充分的分析。未发现能鉴定任何一个（细胞型纯合）样本中所有或大多数成年雌性的同工酶电形态。
