Gambusia affinis (western mosquitofish) serves as a host for a variety of larval and adult parasites. Gambusia affinis is also an incipient matrotroph, exhibiting adjustments in post-fertilization provisioning to some offspring within a brood using recently acquired resources. Nutrient transfer to embryos is expected to limit the loss of embryo mass during development resulting in larger offspring. Since larger offspring are more likely to survive, maternal contributions are expected to increase fitness. The presence of parasites, particularly intestinal helminths, potentially reduces body condition and resources available for developing offspring, thereby reducing host fitness. The effects of parasitism on the fitness of G. affinis were investigated in the present study. Fish were collected from 3 sites monthly from June 2015 through August 2016. All helminth parasites were collected during necropsy and identified. Brood size and embryo developmental stage were recorded for each female fish. Additionally, 10 ova/embryos of each developmental stage from each female fish collected from May through August 2016 were haphazardly selected and individually weighed. From 429 female mosquitofish, 5,072 helminths were collected. Brood size varied among collection sites and was positively influenced by maternal body condition, the number of daylight hours, water temperature, and the intensity of both plerocercoid and adult Schyzocotyle acheilognathi. However, brood size was negatively related to the intensity of Neoechinorhynchus cylindratus cystacanth and an increasing number of days between collection and dissection. Embryo weight increased with the presence of either Camallanidae or Contracaecum multipapulatum, embryo developmental stage, and relative host density. These results indicate that some parasitic helminth species negatively affect the fitness of G. affinis, while some positively affect fitness, and that effect can vary with intensity.

中文翻译：

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冈比亚象属中的寄生虫：最初的雌性营养体中的健身作用。

Gambusia affinis（西部蚊子）是各种幼虫和成虫的宿主。Gambusia affinis还是一种原始的自养生物，利用最近获得的资源，对育雏后代中的某些后代进行了调配。营养物质向胚胎的转移有望限制发育过程中导致更大后代的胚胎质量的损失。由于较大的后代更有可能存活，因此预计母体的贡献会增加体质。寄生虫，特别是肠道蠕虫的存在，可能会降低身体状况和可用于发育后代的资源，从而降低宿主的适应性。在本研究中调查了寄生虫对亲和菌的适应性的影响。从2015年6月到2016年8月，每月从3个地点采集鱼。尸检时收集所有寄生虫并鉴定。记录每只雌鱼的卵大小和胚胎发育阶段。此外，从2016年5月至2016年8月收集的每只雌性鱼类的每个发育阶段的10个卵/胚被随机选择并分别称重。从429只雌性蚊子中，收集了5,072个蠕虫。产卵量在采集地点之间有所不同，并受到孕产妇身体状况，日光小时数，水温以及拟除虫菊酯和成年裂殖子蟹（Schizocotyle acheilognathi）强度的积极影响。然而，育雏的大小与新棘皮鱼的囊藻的强度和收集与解剖之间增加的天数成负相关。胚重随着金龟科或多瓣菜的存在，胚胎发育阶段和相对寄主密度的增加而增加。这些结果表明，某些寄生性蠕虫物种对石的适应性产生了负面影响，而对寄生虫的适应性产生了积极影响，并且这种影响会随强度的变化而变化。