Department of Biology, Baylor University, One Bear Place 97388, Waco, TX 76798, USA.
Parasitol Res. 2010 Jun;107(1):75-87. doi: 10.1007/s00436-010-1836-8. Epub 2010 Apr 8.
Gregarines are ubiquitous protozoan parasites that infect arthropods worldwide. More than 1,600 gregarine species have been described, but only a small percentage of invertebrates have been surveyed for these apicomplexan parasites. Adult dragonfly populations were surveyed for gregarines at two reservoirs in Texas, USA for 2 years. Gregarine prevalence and intensity were compared intraspecifically between host genders and reservoirs, among wing loads, and through time. Of the 29 dragonfly species collected, 41% hosted gregarines. Nine of these dragonfly species were previously undocumented as hosts. Among the commonly collected hosts, prevalence ranged from 18 to 52%. Parasites were aggregated among hosts and had a median intensity of five parasites per host. Gregarines were found only in hosts exceeding a minimum wing load, indicating that gregarines are likely not transferred from the naiad to adult during emergence. Prevalence and intensity increased during both years, suggesting that gregarine oocyst viability parallels increasing host population densities and may be short-lived. Prevalence and intensity also differed between dragonfly populations at two reservoirs. Regression analyses revealed that host species, host gender, month, and year were significant explanatory variables related to gregarine prevalence and intensity. Abundant information on odonate distributions, diversity, and mating activities makes dragonfly-gregarine systems excellent avenues for ecological, evolutionary, and parasitological research. Our results emphasize the importance of considering season, hosts, and habitat when studying gregarine-dragonfly ecology.
血孢子虫是一种普遍存在的原生动物寄生虫，感染着全球的节肢动物。已经描述了超过 1600 种血孢子虫，但只有一小部分无脊椎动物被调查过这些顶复门寄生虫。在美国德克萨斯州的两个水库中，对成年蜻蜓种群进行了为期 2 年的血孢子虫调查。在宿主性别和水库之间、在翅膀负荷之间以及随时间比较了血孢子虫的流行率和强度。在所收集的 29 种蜻蜓中，有 41%携带血孢子虫。其中有 9 种蜻蜓以前没有被记录为宿主。在常见的宿主中，流行率范围从 18%到 52%不等。寄生虫在宿主之间聚集，中位数强度为每个宿主 5 个寄生虫。只有超过最小翅膀负荷的宿主才会发现血孢子虫，这表明血孢子虫在稚虫到成虫的变态过程中不太可能从稚虫转移到成虫。在两年中，流行率和强度都有所增加，这表明血孢子虫卵囊的活力与宿主种群密度的增加相平行，而且可能是短暂的。两个水库的蜻蜓种群之间的流行率和强度也存在差异。回归分析表明，宿主物种、宿主性别、月份和年份是与血孢子虫流行率和强度相关的显著解释变量。蜻蜓的分布、多样性和交配活动等丰富信息使蜻蜓-血孢子虫系统成为生态、进化和寄生虫学研究的绝佳途径。我们的研究结果强调了在研究血孢子虫-蜻蜓生态学时，考虑季节、宿主和栖息地的重要性。
