Fourie L J, Belozerov V N, Kok D J
Department of Zoology and Entomology, University of the Orange Free State, Bloemfontein, South Africa.
Exp Appl Acarol. 1996 Aug;20(8):477-81. doi: 10.1007/BF00053311.
The sex ratio is an important parameter which characterizes the state and dynamics of natural populations of animals. Although ixodid ticks are specialized ectoparasites, most species are bisexual and are characterized by a 1:1 sex ratio for their progeny. In natural populations and even in laboratory colonies, biased sex ratios are often observed. Ixodes rubicundus, the Karoo paralysis tick, parasitizes domestic stock and wild ungulates in South Africa. Adults quest from vegetation, can mate off or on the host and males are seldom parasitic. We hypothesized that the sex ratio for I. rubicundus would be 1:1 when observed directly in the progeny but that it would be strongly biased towards females in samples of parasitic adults. The results mostly supported the hypothesis but it was also shown that unexplained and unpredictable variations can occur. On hosts, females dominated strongly, except on adult angora goats where the sex ratio was biased in favour of the males. This disparity may be related to a greater retention of males in the coarse, curly hair of angora goats compared to the other hosts. Monthly variations in the sex ratios of the tick on hosts are believed to be related to the large fluctuations in sex ratios of questing ticks.
性别比例是表征动物自然种群状态和动态的一个重要参数。尽管硬蜱是特化的体外寄生虫，但大多数种类是两性的，其后代的性别比例特征为1:1。在自然种群中，甚至在实验室群体中，经常观察到偏态的性别比例。南非的卡鲁麻痹蜱红硬蜱寄生于家畜和野生有蹄类动物。成虫从植被上寻觅宿主，可在宿主身上或体外交配，且雄性很少寄生。我们推测，直接观察红硬蜱的后代时其性别比例将为1:1，但在寄生成虫样本中其性别比例将强烈偏向雌性。结果大多支持了这一假设，但也表明可能会出现无法解释和不可预测的变化。在宿主身上，雌性占主导地位，除了在成年安哥拉山羊身上，其性别比例偏向雄性。这种差异可能与雄性相比其他宿主更易滞留在安哥拉山羊粗糙卷曲的毛发中有关。宿主上蜱的性别比例的月度变化被认为与寻觅宿主的蜱的性别比例的大幅波动有关。
