Dunn A M, Terry R S, Taneyhill D E
School of Biology, University of Leeds, UK.
Parasitology. 1998 Jul;117 ( Pt 1):21-30. doi: 10.1017/s0031182098002753.
The amphipod Gammarus duebeni harbours several species of vertically transmitted microsporidian parasites. G. Duebeni were collected from 3 localities in the UK. Animals from Budle Bay, Northumberland, were infected with Octosporea effeminans, and those from Millport, Isle of Cumbrae and Fenham Flats, Northumberland were infected with microsporidia of the genus Nosema. We derived expected distributions of parasites per host embryonic cell by modelling parasite transmission as a multitype, Galton-Watson branching process. Parasite prevalence (proportion of females infected) was significantly heterogeneous among localities. Parasite burden in zygotes was much higher for females infected with Nosema than in animals infected with O. effeminans. There was no significant difference between localities in the number of Nosema in the zygotes. Comparison of models and data from 64-cell host embryos showed that the distributions of parasites per cell were consistent with the hypothesis that sorting of parasites into daughter cells is biased for at least 1 cell lineage. Host embryos infected with O. effeminans could expect to contain a growing number of parasites in each cell generation within such biased cell lineages; similar estimates for Nosema predict a decline in the number of parasites per cell within a biased lineage. We discuss the possibility that the 2 species of parasite may be employing different strategies in order to ensure transmission to the next host generation.
双齿长臂虾（Gammarus duebeni）携带多种垂直传播的微孢子虫寄生虫。双齿长臂虾采自英国的3个地点。诺森伯兰郡布德尔湾的虾感染了柔弱八孢虫（Octosporea effeminans），而坎布里亚岛米尔波特和诺森伯兰郡芬纳姆滩涂的虾感染了 Nosema 属的微孢子虫。我们通过将寄生虫传播建模为多类型高尔顿 - 沃森分支过程，得出了每个宿主胚胎细胞中寄生虫的预期分布。寄生虫感染率（受感染雌性的比例）在不同地点之间存在显著差异。感染 Nosema 的雌性受精卵中的寄生虫负荷远高于感染柔弱八孢虫的动物。不同地点受精卵中 Nosema 的数量没有显著差异。对64细胞宿主胚胎的模型和数据进行比较表明，每个细胞中寄生虫的分布与以下假设一致：寄生虫在至少一个细胞谱系中偏向于进入子细胞。在这种有偏向的细胞谱系中，感染柔弱八孢虫的宿主胚胎预计在每个细胞世代中寄生虫数量会不断增加；对 Nosema 的类似估计预测，在有偏向的谱系中每个细胞内寄生虫数量会下降。我们讨论了这两种寄生虫可能采用不同策略以确保传播到下一代宿主的可能性。
