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首页> 外文期刊>Parasitology >Lack of seasonal variation in the life-history strategies of the trematode Coitocaecum parvum: no apparent environmental effect.
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Lack of seasonal variation in the life-history strategies of the trematode Coitocaecum parvum: no apparent environmental effect.

机译：短小吸虫的生活史策略缺乏季节性变化：没有明显的环境影响。

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摘要

Parasites with complex life cycles have developed numerous and very diverse adaptations to increase the likelihood of completing this cycle. For example, some parasites can abbreviate their life cycles by skipping the definitive host and reproducing inside their intermediate host. The resulting shorter life cycle is clearly advantageous when definitive hosts are absent or rare. In species where life-cycle abbreviation is facultative, this strategy should be adopted in response to seasonally variable environmental conditions. The hermaphroditic trematode Coitocaecum parvum is able to mature precociously (progenesis), and produce eggs by selfing while still inside its amphipod second intermediate host. Several environmental factors such as fish definitive host density and water temperature are known to influence the life-history strategy adopted by laboratory raised C. parvum. Here we document the seasonal variation of environmental parameters and its association with the proportion of progenetic individuals in a parasite population in its natural environment. We found obvious seasonal patterns in both water temperature and C. parvum host densities. However, despite being temporally variable, the proportion of progenetic C. parvum individuals was not correlated with any single parameter. The results show that C. parvum life-history strategy is not as flexible as previously thought. It is possible that the parasite's natural environment contains so many layers of heterogeneity that C. parvum does not possess the ability to adjust its life-history strategy to accurately match the current conditions.
机译：具有复杂生命周期的寄生虫已发展出多种多样的适应方法，以增加完成这一周期的可能性。例如，某些寄生虫可以通过跳过确定的宿主并在其中间宿主内部繁殖来缩短其生命周期。如果没有或很少使用最终宿主，则缩短的生命周期显然是有利的。在生命周期缩写为兼性的物种中，应针对季节性变化的环境条件采用此策略。雌雄同体的拟南芥（Coitocaecum parvum）能够早熟（生殖），并在仍然处于其两足纲第二中间宿主内部的情况下通过自交产生卵。已知几种环境因素（如鱼类的定居宿主密度和水温）会影响实验室饲养的小球藻所采用的生活史策略。在这里，我们记录了环境参数的季节性变化及其与自然环境中寄生虫种群中后代个体的比例的关系。我们发现水温和小球藻寄主密度均存在明显的季节性模式。然而，尽管随时间变化，但后代小球藻个体的比例与任何单个参数均不相关。结果表明，细小隐孢子虫的生活史策略不像以前想象的那样灵活。寄生虫的自然环境可能包含如此多的异质性层，以致小球藻不具备调整其生活史策略以准确匹配当前条件的能力。

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