Abstract：
Ornamental trade has become an important introduction pathway of non-native aquatic species worldwide. Correspondingly, there has been an alarming increase in the number of established crayfish of aquarium origin in Europe over the previous decade. The oomycete Aphanomyces astaci, the pathogen causing crayfish plague responsible for serious declines of European crayfish populations, is dispersed with introduced North American crayfish. The role of ornamental taxa in introducing and spreading different genotypes of this pathogen in open waters remains unclear. We investigated the distribution, prevalence, and diversity of A. astaci in Budapest, Hungary, which became a hotspot of aquarium crayfish introductions. Their establishment in this area was facilitated by locally abundant thermal waters. We screened for A. astaci in six host taxa from 18 sites sampled between 2018 and 2021: five cambarids (Cambarellus patzcuarensis, Faxonius limosus, Procambarus alleni, P. clarkii, P. virginalis) and one native astacid (Pontastacus leptodactylus). The pathogen was confirmed at five sampled sites in four host taxa: P. virginalis, P. clarkii, F. limosus, and for the first time in European open waters also in P. alleni. Genotyping was successful only in individuals from two different brooks where multiple host species coexisted but revealed unexpected patterns. Mitochondrial B-haplogroup of A. astaci, previously usually reported from Pacifastacus leniusculus or infected European species, was detected in P. virginalis at both sites, and in both F. limosus and P. virginalis sampled from a thermally stable tributary of Barát brook in 2018. In contrast, A-haplogroup of A. astaci was detected in coexisting F. limosus, P. virginalis and P. clarkii sampled in the same watercourse just a few hundred meters downstream in 2020. Additional genotyping methods indicated that a previously unknown A. astaci strain was associated with the latter haplogroup. One P. virginalis individual from 2020 was apparently co-infected by strains representing both mitochondrial haplogroups. The results indicated multiple sources of A. astaci in Budapest, likely directly associated with the introduction of ornamental species, interspecific transmission of this pathogen among ornamental hosts, and potential for a quick spatial or temporal turnover of dominant A. astaci strains at a certain locality. This highlights that in regions with high richness of potential A. astaci hosts, host taxon/pathogen genotype combinations become unpredictable, which might prevent reliable genotyping of pathogen sources in local crayfish mass mortalities.
摘要：
观赏贸易已成为全球非本地水生物种的重要引进途径。相应地,在过去的十年中，欧洲水族馆起源的小龙虾数量惊人地增加。卵菌阿番酵母，导致小龙虾瘟疫的病原体是导致欧洲小龙虾种群严重减少的原因，被引入的北美小龙虾分散。观赏类群在开放水域中引入和传播该病原体的不同基因型中的作用尚不清楚。我们调查了分布，患病率,以及布达佩斯A.astaci的多样性，匈牙利,这成为水族馆小龙虾引进的热点。当地丰富的热水促进了他们在该地区的建立。我们在2018年至2021年之间采样的18个地点的6个宿主分类单元中筛选了A.astaci：5个山葵（Cambarelluspatzcuarensis，Faxoniuslimosus,Procambarusalleni,P.clarkii,virginalis）和一种天然的胃酸（Pontastacusleptodactylus）。在四个宿主分类群的五个采样点确认了病原体：virginalis，P.clarkii,F.Limosus,第一次在欧洲开放水域也在P.基因分型仅在来自两个不同小溪的个体中成功，其中多个宿主物种共存，但揭示了意想不到的模式。A.astaci的线粒体B-单倍群，以前通常从Pacifastacusleniusculus或受感染的欧洲物种报告，在这两个部位都检测到了P.virginalis，以及2018年从Barát溪的热稳定支流中采样的F.limosus和P.virginalis。相比之下,在共存的F.limosus中检测到A.astaci的A-单倍群，2020年，virginalis和clarkii在下游几百米的同一水道中采样。另外的基因分型方法表明，以前未知的阿司奇菌株与后者的单倍群相关。从2020年开始，一个virginalis个体显然被代表两种线粒体单倍群的菌株共同感染。结果表明布达佩斯有多种来源的astaci，可能与观赏物种的引入直接相关，这种病原体在观赏宿主之间的种间传播，以及在某一地区优势阿司奇菌株快速时空更替的潜力。这突出表明，在具有高丰富度的潜在A.astaci寄主的地区，宿主分类单元/病原体基因型组合变得不可预测，这可能会阻止当地小龙虾大量死亡率中病原体来源的可靠基因分型。
