Hammoud Cyril, Kayenbergh Annelies, Tumusiime Julius, Verschuren Dirk, Albrecht Christian, Huyse Tine, Van Bocxlaer Bert
Ghent University, Limnology Unit, Department of Biology, B-9000, Gent, Belgium.
Royal Museum for Central Africa, Department of Biology, B-3080, Tervuren, Belgium.
Int J Parasitol Parasites Wildl. 2022 Jul 20;18:300-311. doi: 10.1016/j.ijppaw.2022.07.003. eCollection 2022 Aug.
Trematodes can increase intraspecific variation in the phenotype of their intermediate snail host. However, the extent of such phenotypic changes remains unclear. We investigated the influence of trematode infection on the shell morphology of , a common host of medically important trematodes. We focused on a snail population from crater lake Kasenda (Uganda). We sampled a single homogeneous littoral habitat to minimize the influence of environmental variation on shell phenotype, and barcoded snails to document snail genotypic variation. Among the 257 adult snails analysed, 99 tested positive for trematode infection using rapid-diagnostic PCRs. Subsequently we used high-throughput amplicon sequencing to identify the trematode (co-)infections. For 86 out of the 99 positive samples trematode species delineation could discriminate among combinations of (co-)infection by 11 trematode species. To avoid confounding effects, we focused on four prevalent trematode species. We performed landmark-based geometric morphometrics to characterize shell phenotype and used regressions to examine whether shell size and shape were affected by trematode infection and the developmental stage of infection (as inferred from read counts). Snails infected by sp. 5, sp. or sp. 2 had larger shells than uninfected snails or than those infected by Plagiorchiida sp. Moreover, the shell shape of snails infected solely by sp. 5 differed significantly from that of uninfected snails and snails infected with other trematodes, except from sp. 2. Shape changes included a more protuberant apex, an inward-folded outer apertural lip and a more adapically positioned umbilicus. Size differences were more pronounced in snails with 'late' infections (>25 days) compared to earlier-stage infections. No phenotypic differences were found between snails infected by a single trematode species and those harbouring co-infections. Further work is required to assess the complex causal links between trematode infections and shell morphological alterations of snail hosts.
吸虫可增加其中间螺宿主表型的种内变异。然而，这种表型变化的程度仍不清楚。我们研究了吸虫感染对一种医学上重要吸虫的常见宿主——[螺的名称未给出]贝壳形态的影响。我们重点研究了来自乌干达卡森达火山口湖的一个螺种群。我们在一个单一的同质沿岸栖息地进行采样，以尽量减少环境变异对贝壳表型的影响，并对螺进行条形码编码以记录螺的基因型变异。在分析的257只成年螺中，99只通过快速诊断PCR检测出吸虫感染呈阳性。随后，我们使用高通量扩增子测序来鉴定吸虫（共）感染情况。在99个阳性样本中的86个样本中，吸虫物种划分能够区分11种吸虫（共）感染的组合情况。为避免混淆效应，我们重点关注了四种常见的吸虫物种。我们进行了基于地标点的几何形态测量来表征贝壳表型，并使用回归分析来检验贝壳大小和形状是否受到吸虫感染及其感染发育阶段（根据读数计数推断）的影响。感染了[吸虫物种5名称未给出]、[吸虫物种名称未给出]或[吸虫物种2名称未给出]的螺比未感染的螺或感染了斜睾目吸虫的螺有更大的贝壳。此外，仅感染[吸虫物种5名称未给出]的螺的贝壳形状与未感染的螺以及感染其他吸虫的螺（除[吸虫物种2名称未给出]外）有显著差异。形状变化包括更突出的顶端、向内折叠的外唇孔和更靠近顶端的脐。与早期感染相比，“晚期”感染（>25天）的螺的大小差异更明显。在感染单一吸虫物种的螺和有混合感染的螺之间未发现表型差异。需要进一步开展工作来评估吸虫感染与螺宿主贝壳形态改变之间复杂的因果关系。
