Childress Jasmine N, Rogers Sean C, Bolek Matt G, Langford Gabriel J
Department of Biology, Florida Southern College, Lakeland, Florida 33801.
J Parasitol. 2017 Dec;103(6):663-668. doi: 10.1645/17-30. Epub 2017 Jul 21.
Phenotypic plasticity is a process in which multiple phenotypes arise from 1 genotype because of environmental selection pressures. Gyrinicola batrachiensis has a heterogeneous reproductive strategy such that females reproduce either via parthogenesis with thick-shelled eggs in a single uterus or sexual reproduction with thick- and thin-shelled eggs in separate uterine horns. No evidence exists that strains of G. batrachiensis are able to switch between parthenogenetic and sexual reproduction. Thin-shelled eggs are autoinfective, and thick-shelled eggs act as transmission agents once shed into the aquatic environment. Our primary goal was to determine whether dioecious, didelphic pinworms that infect Rana sphenocephala, a slow-developing tadpole, and Osteopilus septentrionalis, a quick-developing tadpole, display reproductive plasticity with concern to thick- and thin-egg development. We performed experimental cross-infections in aquatic mesocosms to determine if dioecious, didelphic worms vary (based on tadpole host) in their ability to produce thin-shelled eggs: O. septentrionalis (hylid) egg masses were exposed to infected R. sphenocephala (ranid) tadpoles, ranid egg masses to infected hylid tadpoles, and a fully crossed infection that exposed ranid and hylid egg masses to infected tadpoles of both anuran families. Results indicated that worms reproduced via didelphic haplodiploidy in experimental ranid and hylid hosts, but that worms from hylids produced only thick-shelled eggs, which supports an intermediate reproductive strategy in O. septentrionalis. There was a significant difference in the mean intensities of ranid and hylid hosts, supporting our assertion that females infecting ranids are capable of producing autoinfective, thin-shelled eggs, and females infecting hylids do not produce such thin-shelled, autoinfective eggs because of the host microenvironment.
表型可塑性是指由于环境选择压力，单一基因型产生多种表型的过程。蛙栖筒线虫具有异质的繁殖策略，即雌性要么通过孤雌生殖在单个子宫内产生厚壳卵，要么通过有性生殖在不同的子宫角产生厚壳卵和薄壳卵。没有证据表明蛙栖筒线虫菌株能够在孤雌生殖和有性生殖之间切换。薄壳卵具有自身感染性，厚壳卵一旦排入水生环境则充当传播媒介。我们的主要目标是确定感染发育缓慢的蝌蚪——斯氏林蛙和发育迅速的蝌蚪——北方棱蛙的雌雄异体、双子宫蛲虫，在厚卵和薄卵发育方面是否表现出繁殖可塑性。我们在水生微宇宙中进行了实验性交叉感染，以确定雌雄异体、双子宫线虫（基于蝌蚪宿主）产生薄壳卵的能力是否存在差异：将北方棱蛙（雨蛙科）的卵团暴露于感染的斯氏林蛙（蛙科）蝌蚪中；将蛙科的卵团暴露于感染的雨蛙科蝌蚪中；以及进行完全交叉感染，将蛙科和雨蛙科的卵团暴露于两个无尾目科感染的蝌蚪中。结果表明，线虫在实验性的蛙科和雨蛙科宿主中通过双子宫单倍二倍体进行繁殖，但雨蛙科的线虫只产生厚壳卵，这支持了北方棱蛙的中间繁殖策略。蛙科和雨蛙科宿主的平均感染强度存在显著差异，这支持了我们的观点，即感染蛙科的雌性能够产生具有自身感染性的薄壳卵，而感染雨蛙科的雌性由于宿主微环境不会产生这种薄壳的、具有自身感染性的卵。
